1.\" Copyright (c) 2007 The DragonFly Project. All rights reserved. 2.\" 3.\" This code is derived from software contributed to The DragonFly Project 4.\" by Matthew Dillon <dillon@backplane.com> 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in 14.\" the documentation and/or other materials provided with the 15.\" distribution. 16.\" 3. Neither the name of The DragonFly Project nor the names of its 17.\" contributors may be used to endorse or promote products derived 18.\" from this software without specific, prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25.\" INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.Dd April 9, 2016 34.Dt HAMMER 8 35.Os 36.Sh NAME 37.Nm hammer 38.Nd HAMMER file system utility 39.Sh SYNOPSIS 40.Nm 41.Fl h 42.Nm 43.Op Fl 2ABFqrvXy 44.Op Fl b Ar bandwidth 45.Op Fl C Ar cachesize Ns Op Ns Cm \&: Ns Ar readahead 46.Op Fl R Ar restrictcmd 47.Op Fl T Ar restrictpath 48.Op Fl c Ar cyclefile 49.Op Fl e Ar scoreboardfile 50.Op Fl f Ar blkdevs 51.\" .Op Fl s Ar linkpath 52.Op Fl i Ar delay 53.Op Fl p Ar ssh-port 54.Op Fl S Ar splitsize 55.Op Fl t Ar seconds 56.Op Fl m Ar memlimit 57.Ar command 58.Op Ar argument ... 59.Sh DESCRIPTION 60This manual page documents the 61.Nm 62utility which provides miscellaneous functions related to managing a 63.Nm HAMMER 64file system. 65For a general introduction to the 66.Nm HAMMER 67file system, its features, and 68examples on how to set up and maintain one, see 69.Xr HAMMER 5 . 70.Pp 71The options are as follows: 72.Bl -tag -width indent 73.It Fl 2 74Tell the mirror commands to use a 2-way protocol, which allows 75automatic negotiation of transaction id ranges. 76This option is automatically enabled by the 77.Cm mirror-copy 78command. 79.It Fl A 80Make per PFS commands perform on all PFSs if possible. 81If the command supports this option, it targets all PFSs of the 82.Nm HAMMER 83filesystem that the 84.Ar filesystem 85argument (of that command) belongs to. 86Currently 87.Cm rebalance , 88.Cm reblock , 89.Cm reblock-btree , 90.Cm reblock-inodes , 91.Cm reblock-dirs 92and 93.Cm reblock-data 94commands support this option. 95If the command does not support this option, it does nothing. 96.It Fl B 97Bulk transfer. 98.Cm Mirror-stream 99will not attempt to break-up large initial bulk transfers into smaller 100pieces. 101This can save time but if the link is lost in the middle of the 102initial bulk transfer you will have to start over from scratch. 103For more information see the 104.Fl S 105option. 106.It Fl b Ar bandwidth 107Specify a bandwidth limit in bytes per second for mirroring streams. 108This option is typically used to prevent batch mirroring operations from 109loading down the machine. 110The bandwidth may be suffixed with 111.Cm k , m , 112or 113.Cm g 114to specify values in kilobytes, megabytes, and gigabytes per second. 115If no suffix is specified, bytes per second is assumed. 116.Pp 117Unfortunately this is only applicable to the pre-compression bandwidth 118when compression is used, so a better solution would probably be to 119use a 120.Xr ipfw 8 121pipe or a 122.Xr pf 4 123queue. 124.It Fl C Ar cachesize Ns Op Ns Cm \&: Ns Ar readahead 125Set the memory cache size for any raw 126.Tn I/O . 127The default is 16MB. 128A suffix of 129.Cm k 130for kilobytes and 131.Cm m 132for megabytes is allowed, 133else the cache size is specified in bytes. 134.Pp 135The read-behind/read-ahead defaults to 4 136.Nm HAMMER 137blocks. 138.Pp 139This option is typically only used with diagnostic commands 140as kernel-supported commands will use the kernel's buffer cache. 141.It Fl R Ar restrictcmd 142This option is used by hammer ssh-remote to restrict the command later 143on in the argument list. Multiple commands may be specified, separated 144by a comma (all one argument). 145.It Fl T Ar restrictpath 146This option is used by hammer ssh-remote to restrict the filesystem path 147specified later on in the argument list. 148.It Fl c Ar cyclefile 149When pruning, rebalancing or reblocking you can tell the utility 150to start at the object id stored in the specified file. 151If the file does not exist 152.Nm 153will start at the beginning. 154If 155.Nm 156is told to run for a specific period of time 157.Pq Fl t 158and is unable to complete the operation it will write out 159the current object id so the next run can pick up where it left off. 160If 161.Nm 162runs to completion it will delete 163.Ar cyclefile . 164.It Fl e Ar scoreboardfile 165Update scoreboard file with progress, primarily used by mirror-stream. 166.It Fl F 167Force operation. 168E.g.\& 169.Cm cleanup 170will not check that time period has elapsed if this option is given. 171.It Fl f Ar blkdevs 172Specify the volumes making up a 173.Nm HAMMER 174file system. 175.Ar Blkdevs 176is a colon-separated list of devices, each specifying a 177.Nm HAMMER 178volume. 179.It Fl h 180Show usage. 181.It Fl i Ar delay 182Specify delay in seconds for 183.Cm mirror-read-stream . 184When maintaining a streaming mirroring this option specifies the 185minimum delay after a batch ends before the next batch is allowed 186to start. 187The default is five seconds. 188.It Fl m Ar memlimit 189Specify the maximum amount of memory 190.Nm 191will allocate during a dedup pass. 192Specify a suffix 'm', 'g', or 't' for megabytes, gigabytes, or terabytes. 193By default 194.Nm 195will allocate up to 1G of ram to hold CRC/SHA tables while running dedup. 196When the limit is reached the dedup code restricts the range of CRCs to 197keep memory use within bounds and runs multiple passes as necessary until 198the entire filesystem has been deduped. 199.It Fl p Ar ssh-port 200Pass the 201.Fl p Ar ssh-port 202option to 203.Xr ssh 1 204when using a remote 205specification for the source and/or destination. 206.It Fl q 207Decrease verboseness. 208May be specified multiple times. 209.It Fl r 210Specify recursion for those commands which support it. 211.It Fl S Ar splitsize 212Specify the bulk splitup size in bytes for mirroring streams. 213When a 214.Cm mirror-stream 215is first started 216.Nm 217will do an initial run-through of the data to calculate good 218transaction ids to cut up the bulk transfers, creating 219restart points in case the stream is interrupted. 220If we don't do this and the stream is interrupted it might 221have to start all over again. 222The default is a 223.Ar splitsize 224of 4GB. 225.Pp 226At the moment the run-through is disk-bandwidth-heavy but some 227future version will limit the run-through to just the B-Tree 228records and not the record data. 229.Pp 230The splitsize may be suffixed with 231.Cm k , m , 232or 233.Cm g 234to specify values in kilobytes, megabytes, or gigabytes. 235If no suffix is specified, bytes is assumed. 236.Pp 237When mirroring very large filesystems the minimum recommended 238split size is 4GB. 239A small split size may wind up generating a great deal of overhead 240but very little actual incremental data and is not recommended. 241.It Fl t Ar seconds 242Specify timeout in seconds. 243When pruning, rebalancing, reblocking or mirror-reading 244you can tell the utility to stop after a certain period of time. 245A value of 0 means unlimited. 246This option is used along with the 247.Fl c Ar cyclefile 248option to prune, rebalance or reblock incrementally. 249.It Fl v 250Increase verboseness. 251May be specified multiple times. 252.It Fl X 253Enable compression for any remote ssh specifications. 254This option is typically used with the mirroring directives. 255.It Fl y 256Force 257.Dq yes 258for interactive questions. 259.El 260.Pp 261The commands are as follows: 262.Bl -tag -width indent 263.\" ==== synctid ==== 264.It Cm synctid Ar filesystem Op Cm quick 265Generate a guaranteed, formal 64-bit transaction id representing the 266current state of the specified 267.Nm HAMMER 268file system. 269The file system will be synced to the media. 270.Pp 271If the 272.Cm quick 273keyword is specified the file system will be soft-synced, meaning that a 274crash might still undo the state of the file system as of the transaction 275id returned but any new modifications will occur after the returned 276transaction id as expected. 277.Pp 278This operation does not create a snapshot. 279It is meant to be used 280to track temporary fine-grained changes to a subset of files and 281will only remain valid for 282.Ql @@ 283access purposes for the 284.Cm prune-min 285period configured for the PFS. 286If you desire a real snapshot then the 287.Cm snapq 288directive may be what you are looking for. 289.\" ==== bstats ==== 290.It Cm bstats Op Ar interval 291Output 292.Nm HAMMER 293B-Tree statistics until interrupted. 294Pause 295.Ar interval 296seconds between each display. 297The default interval is one second. 298.\" ==== iostats ==== 299.It Cm iostats Op Ar interval 300Output 301.Nm HAMMER 302.Tn I/O 303statistics until interrupted. 304Pause 305.Ar interval 306seconds between each display. 307The default interval is one second. 308.\" ==== stats ==== 309.It Cm stats Op Ar interval 310Output 311.Nm HAMMER 312B-Tree and 313.Tn I/O 314statistics until interrupted. 315Pause 316.Ar interval 317seconds between each display. 318The default interval is one second. 319.\" ==== history ==== 320.It Cm history Ns Oo Cm @ Ns Ar offset Ns Oo Cm \&, Ns Ar length Oc Oc Ar path Ns Oo Cm @ Ns Ar offset Ns Oo Cm \&, Ns Ar length Oc Oc Ar ... 321Show the modification history for inode and data of 322.Nm HAMMER 323files. 324If 325.Ar offset 326is given history is shown for data block at given offset, 327otherwise history is shown for inode. 328If 329.Fl v 330is specified 331.Ar length 332data bytes at given offset are dumped for each version, 333default is 32. 334.Pp 335For each 336.Ar path 337this directive shows object id and sync status, 338and for each object version it shows transaction id and time stamp. 339Files has to exist for this directive to be applicable, 340to track inodes which has been deleted or renamed see 341.Xr undo 1 . 342.Pp 343Different 344.Ar offset 345and 346.Ar length 347can be used for each 348.Ar path 349by specifying 350.Ar offset 351and 352.Ar length 353for each 354.Ar path . 355.\" ==== blockmap ==== 356.It Cm blockmap 357Dump the blockmap for the file system. 358The 359.Nm HAMMER 360blockmap is two-layer 361blockmap representing the maximum possible file system size of 1 Exabyte. 362Needless to say the second layer is only present for blocks which exist. 363.Nm HAMMER Ns 's 364blockmap represents 8-Megabyte blocks, called big-blocks. 365Each big-block has an append 366point, a free byte count, and a typed zone id which allows content to be 367reverse engineered to some degree. 368.Pp 369In 370.Nm HAMMER 371allocations are essentially appended to a selected big-block using 372the append offset and deducted from the free byte count. 373When space is freed the free byte count is adjusted but 374.Nm HAMMER 375does not track holes in big-blocks for reallocation. 376A big-block must be completely freed, either 377through normal file system operations or through reblocking, before 378it can be reused. 379.Pp 380Data blocks can be shared by deducting the space used from the free byte 381count for each shared references. 382This means the free byte count can legally go negative. 383.Pp 384This command needs the 385.Fl f Ar blkdevs 386option. 387.\" ==== checkmap ==== 388.It Cm checkmap 389Check the blockmap allocation count. 390.Nm 391will scan the freemap, B-Tree, UNDO/REDO FIFO, then collect allocation information, 392and construct a blockmap in-memory. 393It will then check that blockmap against the on-disk blockmap. 394.Pp 395This command needs the 396.Fl f Ar blkdevs 397option. 398.\" ==== show ==== 399.It Cm show Op Ar localization Ns Op Cm \&: Ns Ar object_id Ns Op Cm \&: Ns Ar rec_type Ns Op Cm \&: Ns Ar key Ns Op Cm \&: Ns Ar create_tid 400Dump the B-Tree. 401By default this command will validate all B-Tree 402linkages and CRCs, including data CRCs, and will report the most verbose 403information it can dig up. 404Any errors will show up with a 405.Ql B 406in column 1 along with various 407other error flags. 408.Pp 409If you specify 410.Ar localization 411or 412.Ar localization Ns Cm \&: Ns Ar object_id 413or 414.Ar localization Ns Cm \&: Ns Ar object_id Ns Cm \&: Ns Ar rec_type 415or 416.Ar localization Ns Cm \&: Ns Ar object_id Ns Cm \&: Ns Ar rec_type Ns Cm \&: Ns Ar key 417or 418.Ar localization Ns Cm \&: Ns Ar object_id Ns Cm \&: Ns Ar rec_type Ns Cm \&: Ns Ar key Ns Cm \&: Ns Ar create_tid 419the dump will 420search for the key printing nodes as it recurses down, and then 421will iterate forwards. 422These fields are specified in HEX. 423Note that the PFS id is the top 16 bits of the 32-bit localization 424field so PFS#1 would be 00010000. 425.Pp 426If you use 427.Fl q 428the command will report less information about the inode contents. 429.Pp 430If you use 431.Fl qq 432the command will not report the content of the inode or other typed 433data at all. 434.Pp 435If you use 436.Fl qqq 437the command will not report volume header information, big-block fill 438ratios, mirror transaction ids, or report or check data CRCs. 439B-Tree CRCs and linkages are still checked. 440.Pp 441This command needs the 442.Fl f Ar blkdevs 443option. 444.\" ==== show-undo ==== 445.It Cm show-undo 446.Nm ( HAMMER 447VERSION 4+) 448Dump the UNDO/REDO map. 449.Pp 450This command needs the 451.Fl f Ar blkdevs 452option. 453.\" .It Ar blockmap 454.\" Dump the B-Tree, record, large-data, and small-data blockmaps, showing 455.\" physical block assignments and free space percentages. 456.\" ==== ssh-remote ==== 457.It Cm ssh-remote Ar command Ar targetdir 458Used in a ssh authorized_keys line such as 459command="/sbin/hammer ssh-remote mirror-read /fubarmount" ... to allow 460mirror-read or mirror-write access to a particular subdirectory tree. 461This way you do not have to give shell access to the remote box. 462.Nm 463will obtain the original command line from the SSH_ORIGINAL_COMMAND 464environment variable, validate it against the restriction, and then 465re-exec hammer with the validated arguments. 466.Pp 467The remote hammer command does not allow the 468.Fl c 469or 470.Fl f 471options to be passed in. 472.\" ==== recover ==== 473.It Cm recover Ar targetdir 474Recover data from a corrupted 475.Nm HAMMER 476filesystem. 477This is a low level command which operates on the filesystem image and 478attempts to locate and recover files from a corrupted filesystem. 479The entire image is scanned linearly looking for B-Tree nodes. 480Any node 481found which passes its CRC test is scanned for file, inode, and directory 482fragments and the target directory is populated with the resulting data. 483files and directories in the target directory are initially named after 484the object id and are renamed as fragmentary information is processed. 485.Pp 486This command keeps track of filename/object_id translations and may eat a 487considerably amount of memory while operating. 488.Pp 489This command is literally the last line of defense when it comes to 490recovering data from a dead filesystem. 491.Pp 492This command needs the 493.Fl f Ar blkdevs 494option. 495.\" ==== namekey1 ==== 496.It Cm namekey1 Ar filename 497Generate a 498.Nm HAMMER 49964-bit directory hash for the specified file name, using 500the original directory hash algorithm in version 1 of the file system. 501The low 32 bits are used as an iterator for hash collisions and will be 502output as 0. 503.\" ==== namekey2 ==== 504.It Cm namekey2 Ar filename 505Generate a 506.Nm HAMMER 50764-bit directory hash for the specified file name, using 508the new directory hash algorithm in version 2 of the file system. 509The low 32 bits are still used as an iterator but will start out containing 510part of the hash key. 511.\" ==== namekey32 ==== 512.It Cm namekey32 Ar filename 513Generate the top 32 bits of a 514.Nm HAMMER 51564 bit directory hash for the specified file name. 516.\" ==== info ==== 517.It Cm info Ar dirpath ... 518Show extended information about all 519.Nm HAMMER 520file systems mounted in the system or the one mounted in 521.Ar dirpath 522when this argument is specified. 523.Pp 524The information is divided into sections: 525.Bl -tag -width indent 526.It Volume identification 527General information, like the label of the 528.Nm HAMMER 529filesystem, the number of volumes it contains, the FSID, and the 530.Nm HAMMER 531version being used. 532.It Big-block information 533Big-block statistics, such as total, used, reserved and free big-blocks. 534.It Space information 535Information about space used on the filesystem. 536Currently total size, used, reserved and free space are displayed. 537.It PFS information 538Basic information about the PFSs currently present on a 539.Nm HAMMER 540filesystem. 541.Pp 542.Dq PFS ID 543is the ID of the PFS, with 0 being the root PFS. 544.Dq Snaps 545is the current snapshot count on the PFS. 546.Dq Mounted on 547displays the mount point of the PFS is currently mounted on (if any). 548.El 549.\" ==== cleanup ==== 550.It Cm cleanup Op Ar filesystem ... 551This is a meta-command which executes snapshot, prune, rebalance, dedup 552and reblock commands on the specified 553.Nm HAMMER 554file systems. 555If no 556.Ar filesystem 557is specified this command will clean-up all 558.Nm HAMMER 559file systems in use, including PFS's. 560To do this it will scan all 561.Nm HAMMER 562and 563.Nm null 564mounts, extract PFS id's, and clean-up each PFS found. 565.Pp 566This command will access a snapshots 567directory and a configuration file for each 568.Ar filesystem , 569creating them if necessary. 570.Bl -tag -width indent 571.It Nm HAMMER No version 2- 572The configuration file is 573.Pa config 574in the snapshots directory which defaults to 575.Pa <pfs>/snapshots . 576.It Nm HAMMER No version 3+ 577The configuration file is saved in file system meta-data, see 578.Nm 579.Cm config . 580The snapshots directory defaults to 581.Pa /var/hammer/<pfs> 582.Pa ( /var/hammer/root 583for root mount). 584.El 585.Pp 586The format of the configuration file is: 587.Bd -literal -offset indent 588snapshots <period> <retention-time> [any] 589prune <period> <max-runtime> 590rebalance <period> <max-runtime> 591dedup <period> <max-runtime> 592reblock <period> <max-runtime> 593recopy <period> <max-runtime> 594.Ed 595.Pp 596Defaults are: 597.Bd -literal -offset indent 598snapshots 1d 60d # 0d 0d for PFS /tmp, /var/tmp, /usr/obj 599prune 1d 5m 600rebalance 1d 5m 601#dedup 1d 5m # not enabled by default 602reblock 1d 5m 603recopy 30d 10m 604.Ed 605.Pp 606Time is given with a suffix of 607.Cm d , 608.Cm h , 609.Cm m 610or 611.Cm s 612meaning day, hour, minute and second. 613.Pp 614If the 615.Cm snapshots 616directive has a period of 0 and a retention time of 0 617then snapshot generation is disabled, removal of old snapshots are 618disabled, and prunes will use 619.Cm prune-everything . 620.Pp 621If the 622.Cm snapshots 623directive has a period of 0 but a non-zero retention time 624then this command will not create any new snapshots but will remove old 625snapshots it finds based on the retention time. 626This form should be 627used on PFS masters where you are generating your own snapshot softlinks 628manually and on PFS slaves when all you wish to do is prune away existing 629snapshots inherited via the mirroring stream. 630.Pp 631By default only snapshots in the form 632.Ql snap- Ns Ar yyyymmdd Ns Op - Ns Ar HHMM 633are processed. 634If the 635.Cm any 636directive is specified as a third argument on the 637.Cm snapshots 638config line then any softlink of the form 639.Ql *- Ns Ar yyyymmdd Ns Op - Ns Ar HHMM 640or 641.Ql *. Ns Ar yyyymmdd Ns Op - Ns Ar HHMM 642will be processed. 643.Pp 644A period of 0 for prune, rebalance, dedup, reblock or recopy disables the directive. 645A max-runtime of 0 means unlimited. 646.Pp 647If period hasn't passed since the previous 648.Cm cleanup 649run nothing is done. 650For example a day has passed when midnight is passed (localtime). 651If the 652.Fl F 653flag is given the period is ignored. 654By default, 655.Dx 656is set up to run 657.Nm Cm cleanup 658nightly via 659.Xr periodic 8 . 660.Pp 661The default configuration file will create a daily snapshot, do a daily 662pruning, rebalancing, deduping and reblocking run and a monthly recopy run. 663Reblocking is defragmentation with a level of 95%, 664and recopy is full defragmentation. 665.Pp 666By default prune, dedup and rebalance operations are time limited to 5 minutes, 667and reblock operations to a bit over 5 minutes, 668and recopy operations to a bit over 10 minutes. 669Reblocking and recopy runs are each broken down into four separate functions: 670B-Tree, inodes, dirs and data. 671Each function is time limited to the time given in the configuration file, 672but the B-Tree, inodes and dirs functions usually does not take very long time, 673full defragmentation is always used for these three functions. 674Also note that this directive will by default disable snapshots on 675the following PFS's: 676.Pa /tmp , 677.Pa /var/tmp 678and 679.Pa /usr/obj . 680.Pp 681The defaults may be adjusted by modifying the configuration file. 682The pruning and reblocking commands automatically maintain a cyclefile 683for incremental operation. 684If you interrupt (^C) the program the cyclefile will be updated, 685but a sub-command 686may continue to run in the background for a few seconds until the 687.Nm HAMMER 688ioctl detects the interrupt. 689The 690.Cm snapshots 691PFS option can be set to use another location for the snapshots directory. 692.Pp 693Work on this command is still in progress. 694Expected additions: 695An ability to remove snapshots dynamically as the 696file system becomes full. 697.\" ==== abort-cleanup ==== 698.It Cm abort-cleanup 699This command will terminate all active 700.Cm cleanup 701processes. 702.\" ==== config ==== 703.It Cm config Op Ar filesystem Op Ar configfile 704.Nm ( HAMMER 705VERSION 3+) 706Show or change configuration for 707.Ar filesystem . 708If zero or one arguments are specified this function dumps the current 709configuration file to stdout. 710Zero arguments specifies the PFS containing the current directory. 711This configuration file is stored in file system meta-data. 712If two arguments are specified this function installs a new configuration file 713.Ar configfile . 714.Pp 715In 716.Nm HAMMER 717versions less than 3 the configuration file is by default stored in 718.Pa <pfs>/snapshots/config , 719but in all later versions the configuration file is stored in file system 720meta-data. 721.\" ==== viconfig ==== 722.It Cm viconfig Op Ar filesystem 723.Nm ( HAMMER 724VERSION 3+) 725Edit the configuration file and reinstall into file system meta-data when done. 726Zero arguments specifies the PFS containing the current directory. 727.\" ==== volume-add ==== 728.It Cm volume-add Ar device Ar filesystem 729Add volume 730.Ar device 731to 732.Ar filesystem . 733This will format 734.Ar device 735and add all of its space to 736.Ar filesystem . 737A 738.Nm HAMMER 739file system can use up to 256 volumes. 740.Pp 741.Em NOTE! 742All existing data contained on 743.Ar device 744will be destroyed by this operation! 745If 746.Ar device 747contains a valid 748.Nm HAMMER 749file system, formatting will be denied. 750You can overcome this sanity check by using 751.Xr dd 1 752to erase the beginning sectors of the device. 753.Pp 754Remember that you have to specify 755.Ar device , 756together with any other device that make up the file system, 757colon-separated to 758.Pa /etc/fstab 759and 760.Xr mount_hammer 8 . 761If 762.Ar filesystem 763is root file system, also remember to add 764.Ar device 765to 766.Va vfs.root.mountfrom 767in 768.Pa /boot/loader.conf , 769see 770.Xr loader 8 . 771.\" ==== volume-del ==== 772.It Cm volume-del Ar device Ar filesystem 773Remove volume 774.Ar device 775from 776.Ar filesystem . 777.Pp 778Remember that you have to remove 779.Ar device 780from the colon-separated list in 781.Pa /etc/fstab 782and 783.Xr mount_hammer 8 . 784If 785.Ar filesystem 786is root file system, also remember to remove 787.Ar device 788from 789.Va vfs.root.mountfrom 790in 791.Pa /boot/loader.conf , 792see 793.Xr loader 8 . 794.Pp 795It is not possible to remove the 796.Ar root-volume 797as it contains 798.Ar filesystem 799meta data such as 800.Nm HAMMER Ns 's 801layer1 blockmap and UNDO/REDO FIFO. 802.Pp 803This command may 804.Cm reblock 805filesystem before it attempts to remove the volume if the volume is not empty. 806.\" ==== volume-list ==== 807.It Cm volume-list Ar filesystem 808List the volumes that make up 809.Ar filesystem . 810If -v is specified the command shows volume number for each volume as well as 811.Ar root-volume 812information. 813.\" ==== volume-blkdevs ==== 814.It Cm volume-blkdevs Ar filesystem 815List the volumes that make up 816.Ar filesystem 817in 818.Ar blkdevs 819format. 820.\" ==== snapshot ==== 821.It Cm snapshot Oo Ar filesystem Oc Ar snapshot-dir 822.It Cm snapshot Ar filesystem Ar snapshot-dir Op Ar note 823Take a snapshot of the file system either explicitly given by 824.Ar filesystem 825or implicitly derived from the 826.Ar snapshot-dir 827argument and creates a symlink in the directory provided by 828.Ar snapshot-dir 829pointing to the snapshot. 830If 831.Ar snapshot-dir 832is not a directory, it is assumed to be a format string passed to 833.Xr strftime 3 834with the current time as parameter. 835If 836.Ar snapshot-dir 837refers to an existing directory, a default format string of 838.Ql snap-%Y%m%d-%H%M 839is assumed and used as name for the newly created symlink. 840.Pp 841Snapshot is a per PFS operation, so each PFS in a 842.Nm HAMMER 843file system have to be snapshot separately. 844.Pp 845Example, assuming that 846.Pa /mysnapshots 847is on file system 848.Pa / 849and that 850.Pa /obj 851and 852.Pa /usr 853are file systems on their own, the following invocations: 854.Bd -literal -offset indent 855hammer snapshot /mysnapshots 856 857hammer snapshot /mysnapshots/%Y-%m-%d 858 859hammer snapshot /obj /mysnapshots/obj-%Y-%m-%d 860 861hammer snapshot /usr /my/snaps/usr "note" 862.Ed 863.Pp 864Would create symlinks similar to: 865.Bd -literal -offset indent 866/mysnapshots/snap-20080627-1210 -> /@@0x10d2cd05b7270d16 867 868/mysnapshots/2008-06-27 -> /@@0x10d2cd05b7270d16 869 870/mysnapshots/obj-2008-06-27 -> /obj@@0x10d2cd05b7270d16 871 872/my/snaps/usr/snap-20080627-1210 -> /usr@@0x10d2cd05b7270d16 873.Ed 874.Pp 875When run on a 876.Nm HAMMER 877version 3+ file system the snapshot is also recorded in file system meta-data 878along with the optional 879.Ar note . 880See the 881.Cm snapls 882directive. 883.\" ==== snap* ==== 884.It Cm snap Ar path Op Ar note 885.Nm ( HAMMER 886VERSION 3+) 887Create a snapshot for the PFS containing 888.Ar path 889and create a snapshot softlink. 890If the path specified is a 891directory a standard snapshot softlink will be created in the directory. 892The snapshot softlink points to the base of the mounted PFS. 893.It Cm snaplo Ar path Op Ar note 894.Nm ( HAMMER 895VERSION 3+) 896Create a snapshot for the PFS containing 897.Ar path 898and create a snapshot softlink. 899If the path specified is a 900directory a standard snapshot softlink will be created in the directory. 901The snapshot softlink points into the directory it is contained in. 902.It Cm snapq Ar dir Op Ar note 903.Nm ( HAMMER 904VERSION 3+) 905Create a snapshot for the PFS containing the specified directory but do 906not create a softlink. 907Instead output a path which can be used to access 908the directory via the snapshot. 909.Pp 910An absolute or relative path may be specified. 911The path will be used as-is as a prefix in the path output to stdout. 912As with the other 913snap and snapshot directives the snapshot transaction id will be registered 914in the file system meta-data. 915.It Cm snaprm Ar path Ar ... 916.It Cm snaprm Ar transaction_id Ar ... 917.It Cm snaprm Ar filesystem Ar transaction_id Ar ... 918.Nm ( HAMMER 919VERSION 3+) 920Remove a snapshot given its softlink or transaction id. 921If specifying a transaction id 922the snapshot is removed from file system meta-data but you are responsible 923for removing any related softlinks. 924.Pp 925If a softlink path is specified the filesystem and transaction id 926is derived from the contents of the softlink. 927If just a transaction id is specified it is assumed to be a snapshot in the 928.Nm HAMMER 929filesystem you are currently chdir'd into. 930You can also specify the filesystem and transaction id explicitly. 931.It Cm snapls Op Ar path ... 932.Nm ( HAMMER 933VERSION 3+) 934Dump the snapshot meta-data for PFSs containing each 935.Ar path 936listing all available snapshots and their notes. 937If no arguments are specified snapshots for the PFS containing the 938current directory are listed. 939This is the definitive list of snapshots for the file system. 940.\" ==== prune ==== 941.It Cm prune Ar softlink-dir 942Prune the file system based on previously created snapshot softlinks. 943Pruning is the act of deleting file system history. 944The 945.Cm prune 946command will delete file system history such that 947the file system state is retained for the given snapshots, 948and all history after the latest snapshot. 949By setting the per PFS parameter 950.Cm prune-min , 951history is guaranteed to be saved at least this time interval. 952All other history is deleted. 953.Pp 954The target directory is expected to contain softlinks pointing to 955snapshots of the file systems you wish to retain. 956The directory is scanned non-recursively and the mount points and 957transaction ids stored in the softlinks are extracted and sorted. 958The file system is then explicitly pruned according to what is found. 959Cleaning out portions of the file system is as simple as removing a 960snapshot softlink and then running the 961.Cm prune 962command. 963.Pp 964As a safety measure pruning only occurs if one or more softlinks are found 965containing the 966.Ql @@ 967snapshot id extension. 968Currently the scanned softlink directory must contain softlinks pointing 969to a single 970.Nm HAMMER 971mount. 972The softlinks may specify absolute or relative paths. 973Softlinks must use 20-character 974.Ql @@0x%016llx 975transaction ids, as might be returned from 976.Nm Cm synctid Ar filesystem . 977.Pp 978Pruning is a per PFS operation, so each PFS in a 979.Nm HAMMER 980file system have to be pruned separately. 981.Pp 982Note that pruning a file system may not immediately free-up space, 983though typically some space will be freed if a large number of records are 984pruned out. 985The file system must be reblocked to completely recover all available space. 986.Pp 987Example, lets say your that you didn't set 988.Cm prune-min , 989and snapshot directory contains the following links: 990.Bd -literal -offset indent 991lrwxr-xr-x 1 root wheel 29 May 31 17:57 snap1 -> 992/usr/obj/@@0x10d2cd05b7270d16 993 994lrwxr-xr-x 1 root wheel 29 May 31 17:58 snap2 -> 995/usr/obj/@@0x10d2cd13f3fde98f 996 997lrwxr-xr-x 1 root wheel 29 May 31 17:59 snap3 -> 998/usr/obj/@@0x10d2cd222adee364 999.Ed 1000.Pp 1001If you were to run the 1002.Cm prune 1003command on this directory, then the 1004.Nm HAMMER 1005.Pa /usr/obj 1006mount will be pruned to retain the above three snapshots. 1007In addition, history for modifications made to the file system older than 1008the oldest snapshot will be destroyed and history for potentially fine-grained 1009modifications made to the file system more recently than the most recent 1010snapshot will be retained. 1011.Pp 1012If you then delete the 1013.Pa snap2 1014softlink and rerun the 1015.Cm prune 1016command, 1017history for modifications pertaining to that snapshot would be destroyed. 1018.Pp 1019In 1020.Nm HAMMER 1021file system versions 3+ this command also scans the snapshots stored 1022in the file system meta-data and includes them in the prune. 1023.\" ==== prune-everything ==== 1024.It Cm prune-everything Ar filesystem 1025Remove all historical records from 1026.Ar filesystem . 1027Use this directive with caution on PFSs where you intend to use history. 1028.Pp 1029This command does not remove snapshot softlinks but will delete all 1030snapshots recorded in file system meta-data (for file system version 3+). 1031The user is responsible for deleting any softlinks. 1032.Pp 1033Pruning is a per PFS operation, so each PFS in a 1034.Nm HAMMER 1035file system have to be pruned separately. 1036.\" ==== rebalance ==== 1037.It Cm rebalance Ar filesystem Op Ar saturation_percentage 1038Rebalance the B-Tree, nodes with small number of 1039elements will be combined and element counts will be smoothed out 1040between nodes. 1041.Pp 1042The saturation percentage is between 50% and 100%. 1043The default is 85% (the 1044.Sq % 1045suffix is not needed). 1046.Pp 1047Rebalancing is a per PFS operation, so each PFS in a 1048.Nm HAMMER 1049file system have to be rebalanced separately. 1050.\" ==== dedup ==== 1051.It Cm dedup Ar filesystem 1052.Nm ( HAMMER 1053VERSION 5+) 1054Perform offline (post-process) deduplication. 1055Deduplication occurs at 1056the block level, currently only data blocks of the same size can be 1057deduped, metadata blocks can not. 1058The hash function used for comparing 1059data blocks is CRC-32 (CRCs are computed anyways as part of 1060.Nm HAMMER 1061data integrity features, so there's no additional overhead). 1062Since CRC is a weak hash function a byte-by-byte comparison is done 1063before actual deduping. 1064In case of a CRC collision (two data blocks have the same CRC 1065but different contents) the checksum is upgraded to SHA-256. 1066.Pp 1067Currently 1068.Nm HAMMER 1069reblocker may partially blow up (re-expand) dedup (reblocker's normal 1070operation is to reallocate every record, so it's possible for deduped 1071blocks to be re-expanded back). 1072.Pp 1073Deduplication is a per PFS operation, so each PFS in a 1074.Nm HAMMER 1075file system have to be deduped separately. 1076This also 1077means that if you have duplicated data in two different PFSs that data 1078won't be deduped, however the addition of such feature is planned. 1079.Pp 1080The 1081.Fl m Ar memlimit 1082option should be used to limit memory use during the dedup run if the 1083default 1G limit is too much for the machine. 1084.\" ==== dedup-simulate ==== 1085.It Cm dedup-simulate Ar filesystem 1086Shows potential space savings (simulated dedup ratio) one can get after 1087running 1088.Cm dedup 1089command. 1090If the estimated dedup ratio is greater than 1.00 you will see 1091dedup space savings. 1092Remember that this is an estimated number, in 1093practice real dedup ratio will be slightly smaller because of 1094.Nm HAMMER 1095big-block underflows, B-Tree locking issues and other factors. 1096.Pp 1097Note that deduplication currently works only on bulk data so if you 1098try to run 1099.Cm dedup-simulate 1100or 1101.Cm dedup 1102commands on a PFS that contains metadata only (directory entries, 1103softlinks) you will get a 0.00 dedup ratio. 1104.Pp 1105The 1106.Fl m Ar memlimit 1107option should be used to limit memory use during the dedup run if the 1108default 1G limit is too much for the machine. 1109.\" ==== reblock* ==== 1110.It Cm reblock Ar filesystem Op Ar fill_percentage 1111.It Cm reblock-btree Ar filesystem Op Ar fill_percentage 1112.It Cm reblock-inodes Ar filesystem Op Ar fill_percentage 1113.It Cm reblock-dirs Ar filesystem Op Ar fill_percentage 1114.It Cm reblock-data Ar filesystem Op Ar fill_percentage 1115Attempt to defragment and free space for reuse by reblocking a live 1116.Nm HAMMER 1117file system. 1118Big-blocks cannot be reused by 1119.Nm HAMMER 1120until they are completely free. 1121This command also has the effect of reordering all elements, effectively 1122defragmenting the file system. 1123.Pp 1124The default fill percentage is 100% and will cause the file system to be 1125completely defragmented. 1126All specified element types will be reallocated and rewritten. 1127If you wish to quickly free up space instead try specifying 1128a smaller fill percentage, such as 90% or 80% (the 1129.Sq % 1130suffix is not needed). 1131.Pp 1132Since this command may rewrite the entire contents of the disk it is 1133best to do it incrementally from a 1134.Xr cron 8 1135job along with the 1136.Fl c Ar cyclefile 1137and 1138.Fl t Ar seconds 1139options to limit the run time. 1140The file system would thus be defragmented over long period of time. 1141.Pp 1142It is recommended that separate invocations be used for each data type. 1143B-Tree nodes, inodes, and directories are typically the most important 1144elements needing defragmentation. 1145Data can be defragmented over a longer period of time. 1146.Pp 1147Reblocking is a per PFS operation, so each PFS in a 1148.Nm HAMMER 1149file system have to be reblocked separately. 1150.\" ==== pfs-status ==== 1151.It Cm pfs-status Ar dirpath ... 1152Retrieve the mirroring configuration parameters for the specified 1153.Nm HAMMER 1154file systems or pseudo-filesystems (PFS's). 1155.\" ==== pfs-master ==== 1156.It Cm pfs-master Ar dirpath Op Ar options 1157Create a pseudo-filesystem (PFS) inside a 1158.Nm HAMMER 1159file system. 1160Up to 65536 PFSs can be created. 1161Each PFS uses an independent inode numbering space making it suitable 1162for replication. 1163.Pp 1164The 1165.Cm pfs-master 1166directive creates a PFS that you can read, write, and use as a mirroring 1167source. 1168.Pp 1169A PFS can only be truly destroyed with the 1170.Cm pfs-destroy 1171directive. 1172Removing the softlink will not destroy the underlying PFS. 1173.Pp 1174A PFS can only be created in the root PFS (PFS# 0), 1175not in a PFS created by 1176.Cm pfs-master 1177or 1178.Cm pfs-slave 1179(PFS# >0). 1180.Pp 1181It is recommended that 1182.Ar dirpath 1183is of the form 1184.Pa <fs>/pfs/<name> 1185(i.e.\& located in 1186.Pa PFS 1187directory at root of 1188.Nm HAMMER 1189file system). 1190.Pp 1191It is recommended to use a 1192.Nm null 1193mount to access a PFS, except for root PFS, for more information see 1194.Xr HAMMER 5 . 1195.\" ==== pfs-slave ==== 1196.It Cm pfs-slave Ar dirpath Op Ar options 1197Create a pseudo-filesystem (PFS) inside a 1198.Nm HAMMER 1199file system. 1200Up to 65536 PFSs can be created. 1201Each PFS uses an independent inode numbering space making it suitable 1202for replication. 1203.Pp 1204The 1205.Cm pfs-slave 1206directive creates a PFS that you can use as a mirroring source or target. 1207You will not be able to access a slave PFS until you have completed the 1208first mirroring operation with it as the target (its root directory will 1209not exist until then). 1210.Pp 1211Access to the pfs-slave via the special softlink, as described in the 1212.Sx PSEUDO-FILESYSTEM (PFS) NOTES 1213below, allows 1214.Nm HAMMER 1215to 1216dynamically modify the snapshot transaction id by returning a dynamic result 1217from 1218.Xr readlink 2 1219calls. 1220.Pp 1221A PFS can only be truly destroyed with the 1222.Cm pfs-destroy 1223directive. 1224Removing the softlink will not destroy the underlying PFS. 1225.Pp 1226A PFS can only be created in the root PFS (PFS# 0), 1227not in a PFS created by 1228.Cm pfs-master 1229or 1230.Cm pfs-slave 1231(PFS# >0). 1232.Pp 1233It is recommended that 1234.Ar dirpath 1235is of the form 1236.Pa <fs>/pfs/<name> 1237(i.e.\& located in 1238.Pa PFS 1239directory at root of 1240.Nm HAMMER 1241file system). 1242.Pp 1243It is recommended to use a 1244.Nm null 1245mount to access a PFS, except for root PFS, for more information see 1246.Xr HAMMER 5 . 1247.\" ==== pfs-update ==== 1248.It Cm pfs-update Ar dirpath Op Ar options 1249Update the configuration parameters for an existing 1250.Nm HAMMER 1251file system or pseudo-filesystem. 1252Options that may be specified: 1253.Bl -tag -width indent 1254.It Cm sync-beg-tid= Ns Ar 0x16llx 1255This is the automatic snapshot access starting transaction id for 1256mirroring slaves. 1257This parameter is normally updated automatically by the 1258.Cm mirror-write 1259directive. 1260.Pp 1261It is important to note that accessing a mirroring slave 1262with a transaction id greater than the last fully synchronized transaction 1263id can result in an unreliable snapshot since you will be accessing 1264data that is still undergoing synchronization. 1265.Pp 1266Manually modifying this field is dangerous and can result in a broken mirror. 1267.It Cm sync-end-tid= Ns Ar 0x16llx 1268This is the current synchronization point for mirroring slaves. 1269This parameter is normally updated automatically by the 1270.Cm mirror-write 1271directive. 1272.Pp 1273Manually modifying this field is dangerous and can result in a broken mirror. 1274.It Cm shared-uuid= Ns Ar uuid 1275Set the shared UUID for this file system. 1276All mirrors must have the same shared UUID. 1277For safety purposes the 1278.Cm mirror-write 1279directives will refuse to operate on a target with a different shared UUID. 1280.Pp 1281Changing the shared UUID on an existing, non-empty mirroring target, 1282including an empty but not completely pruned target, 1283can lead to corruption of the mirroring target. 1284.It Cm unique-uuid= Ns Ar uuid 1285Set the unique UUID for this file system. 1286This UUID should not be used anywhere else, 1287even on exact copies of the file system. 1288.It Cm label= Ns Ar string 1289Set a descriptive label for this file system. 1290.It Cm snapshots= Ns Ar string 1291Specify the snapshots directory which 1292.Nm 1293.Cm cleanup 1294will use to manage this PFS. 1295.Bl -tag -width indent 1296.It Nm HAMMER No version 2- 1297The snapshots directory does not need to be configured for 1298PFS masters and will default to 1299.Pa <pfs>/snapshots . 1300.Pp 1301PFS slaves are mirroring slaves so you cannot configure a snapshots 1302directory on the slave itself to be managed by the slave's machine. 1303In fact, the slave will likely have a 1304.Pa snapshots 1305sub-directory mirrored 1306from the master, but that directory contains the configuration the master 1307is using for its copy of the file system, not the configuration that we 1308want to use for our slave. 1309.Pp 1310It is recommended that 1311.Pa <fs>/var/slaves/<name> 1312be configured for a PFS slave, where 1313.Pa <fs> 1314is the base 1315.Nm HAMMER 1316file system, and 1317.Pa <name> 1318is an appropriate label. 1319.It Nm HAMMER No version 3+ 1320The snapshots directory does not need to be configured for PFS masters or 1321slaves. 1322The snapshots directory defaults to 1323.Pa /var/hammer/<pfs> 1324.Pa ( /var/hammer/root 1325for root mount). 1326.El 1327.Pp 1328You can control snapshot retention on your slave independent of the master. 1329.It Cm snapshots-clear 1330Zero out the 1331.Cm snapshots 1332directory path for this PFS. 1333.It Cm prune-min= Ns Ar N Ns Cm d 1334.It Cm prune-min= Ns Oo Ar N Ns Cm d/ Oc Ns \ 1335Ar hh Ns Op Cm \&: Ns Ar mm Ns Op Cm \&: Ns Ar ss 1336Set the minimum fine-grained data retention period. 1337.Nm HAMMER 1338always retains fine-grained history up to the most recent snapshot. 1339You can extend the retention period further by specifying a non-zero 1340pruning minimum. 1341Any snapshot softlinks within the retention period are ignored 1342for the purposes of pruning (i.e.\& the fine grained history is retained). 1343Number of days, hours, minutes and seconds are given as 1344.Ar N , hh , mm 1345and 1346.Ar ss . 1347.Pp 1348Because the transaction id in the snapshot softlink cannot be used 1349to calculate a timestamp, 1350.Nm HAMMER 1351uses the earlier of the 1352.Fa st_ctime 1353or 1354.Fa st_mtime 1355field of the softlink to 1356determine which snapshots fall within the retention period. 1357Users must be sure to retain one of these two fields when manipulating 1358the softlink. 1359.El 1360.\" ==== pfs-upgrade ==== 1361.It Cm pfs-upgrade Ar dirpath 1362Upgrade a PFS from slave to master operation. 1363The PFS will be rolled back to the current end synchronization transaction id 1364(removing any partial synchronizations), and will then become writable. 1365.Pp 1366.Em WARNING! 1367.Nm HAMMER 1368currently supports only single masters and using 1369this command can easily result in file system corruption 1370if you don't know what you are doing. 1371.Pp 1372This directive will refuse to run if any programs have open descriptors 1373in the PFS, including programs chdir'd into the PFS. 1374.\" ==== pfs-downgrade ==== 1375.It Cm pfs-downgrade Ar dirpath 1376Downgrade a master PFS from master to slave operation. 1377The PFS becomes read-only and access will be locked to its 1378.Cm sync-end-tid . 1379.Pp 1380This directive will refuse to run if any programs have open descriptors 1381in the PFS, including programs chdir'd into the PFS. 1382.\" ==== pfs-destroy ==== 1383.It Cm pfs-destroy Ar dirpath 1384This permanently destroys a PFS. 1385.Pp 1386This directive will refuse to run if any programs have open descriptors 1387in the PFS, including programs chdir'd into the PFS. 1388As safety measure the 1389.Fl y 1390flag have no effect on this directive. 1391.\" ==== mirror-read ==== 1392.It Cm mirror-read Ar filesystem Op Ar begin-tid 1393Generate a mirroring stream to stdout. 1394The stream ends when the transaction id space has been exhausted. 1395.Ar filesystem 1396may be a master or slave PFS. 1397.\" ==== mirror-read-stream ==== 1398.It Cm mirror-read-stream Ar filesystem Op Ar begin-tid 1399Generate a mirroring stream to stdout. 1400Upon completion the stream is paused until new data is synced to the 1401.Ar filesystem , 1402then resumed. 1403Operation continues until the pipe is broken. 1404See the 1405.Cm mirror-stream 1406command for more details. 1407.\" ==== mirror-write ==== 1408.It Cm mirror-write Ar filesystem 1409Take a mirroring stream on stdin. 1410.Ar filesystem 1411must be a slave PFS. 1412.Pp 1413This command will fail if the 1414.Cm shared-uuid 1415configuration field for the two file systems do not match. 1416See the 1417.Cm mirror-copy 1418command for more details. 1419.Pp 1420If the target PFS does not exist this command will ask you whether 1421you want to create a compatible PFS slave for the target or not. 1422.\" ==== mirror-dump ==== 1423.It Ar mirror-dump Ar [header] 1424A 1425.Cm mirror-read 1426can be piped into a 1427.Cm mirror-dump 1428to dump an ASCII representation of the mirroring stream. 1429If the keyword 1430.Ar header 1431is specified, only the header information is shown. 1432.\" ==== mirror-copy ==== 1433.\".It Cm mirror-copy Ar [[user@]host:]filesystem [[user@]host:]filesystem 1434.It Cm mirror-copy \ 1435Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \ 1436Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem 1437This is a shortcut which pipes a 1438.Cm mirror-read 1439command to a 1440.Cm mirror-write 1441command. 1442If a remote host specification is made the program forks a 1443.Xr ssh 1 1444(or other program as specified by the 1445.Ev HAMMER_RSH 1446environment variable) and execs the 1447.Cm mirror-read 1448and/or 1449.Cm mirror-write 1450on the appropriate host. 1451The source may be a master or slave PFS, and the target must be a slave PFS. 1452.Pp 1453This command also establishes full duplex communication and turns on 1454the 2-way protocol feature 1455.Fl ( 2 ) 1456which automatically negotiates transaction id 1457ranges without having to use a cyclefile. 1458If the operation completes successfully the target PFS's 1459.Cm sync-end-tid 1460will be updated. 1461Note that you must re-chdir into the target PFS to see the updated information. 1462If you do not you will still be in the previous snapshot. 1463.Pp 1464If the target PFS does not exist this command will ask you whether 1465you want to create a compatible PFS slave for the target or not. 1466.\" ==== mirror-stream ==== 1467.\".It Cm mirror-stream Ar [[user@]host:]filesystem [[user@]host:]filesystem 1468.It Cm mirror-stream \ 1469Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \ 1470Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem 1471This is a shortcut which pipes a 1472.Cm mirror-read-stream 1473command to a 1474.Cm mirror-write 1475command. 1476This command works similarly to 1477.Cm mirror-copy 1478but does not exit after the initial mirroring completes. 1479The mirroring operation will resume as changes continue to be made to the 1480source. 1481The command is commonly used with 1482.Fl i Ar delay 1483and 1484.Fl b Ar bandwidth 1485options to keep the mirroring target in sync with the source on a continuing 1486basis. 1487.Pp 1488If the pipe is broken the command will automatically retry after sleeping 1489for a short while. 1490The time slept will be 15 seconds plus the time given in the 1491.Fl i 1492option. 1493.Pp 1494This command also detects the initial-mirroring case and spends some 1495time scanning the B-Tree to find good break points, allowing the initial 1496bulk mirroring operation to be broken down into 4GB pieces. 1497This means that the user can kill and restart the operation and it will 1498not have to start from scratch once it has gotten past the first chunk. 1499The 1500.Fl S 1501option may be used to change the size of pieces and the 1502.Fl B 1503option may be used to disable this feature and perform an initial bulk 1504transfer instead. 1505.\" ==== version ==== 1506.It Cm version Ar filesystem 1507This command returns the 1508.Nm HAMMER 1509file system version for the specified 1510.Ar filesystem 1511as well as the range of versions supported in the kernel. 1512The 1513.Fl q 1514option may be used to remove the summary at the end. 1515.\" ==== version-upgrade ==== 1516.It Cm version-upgrade Ar filesystem Ar version Op Cm force 1517Upgrade the 1518.Nm HAMMER 1519.Ar filesystem 1520to the specified 1521.Ar version . 1522Once upgraded a file system may not be downgraded. 1523If you wish to upgrade a file system to a version greater or equal to the 1524work-in-progress (WIP) version number you must specify the 1525.Cm force 1526directive. 1527Use of WIP versions should be relegated to testing and may require wiping 1528the file system as development progresses, even though the WIP version might 1529not change. 1530.Pp 1531.Em NOTE! 1532This command operates on the entire 1533.Nm HAMMER 1534file system and is not a per PFS operation. 1535All PFS's will be affected. 1536.Bl -tag -width indent 1537.It 1 1538.Dx 2.0 1539default version, first 1540.Nm HAMMER 1541release. 1542.It 2 1543.Dx 2.3 . 1544New directory entry layout. 1545This version is using a new directory hash key. 1546.It 3 1547.Dx 2.5 . 1548New snapshot management, using file system meta-data for saving 1549configuration file and snapshots (transaction ids etc.). 1550Also default snapshots directory has changed. 1551.It 4 1552.Dx 2.6 1553default version. 1554New undo/redo/flush, giving 1555.Nm HAMMER 1556a much faster sync and fsync. 1557.It 5 1558.Dx 2.9 . 1559Deduplication support. 1560.It 6 1561.Dx 2.9 . 1562Directory hash ALG1. 1563Tends to maintain inode number / directory name entry ordering better 1564for files after minor renaming. 1565.El 1566.El 1567.Sh PSEUDO-FILESYSTEM (PFS) NOTES 1568The root of a PFS is not hooked into the primary 1569.Nm HAMMER 1570file system as a directory. 1571Instead, 1572.Nm HAMMER 1573creates a special softlink called 1574.Ql @@PFS%05d 1575(exactly 10 characters long) in the primary 1576.Nm HAMMER 1577file system. 1578.Nm HAMMER 1579then modifies the contents of the softlink as read by 1580.Xr readlink 2 , 1581and thus what you see with an 1582.Nm ls 1583command or if you were to 1584.Nm cd 1585into the link. 1586If the PFS is a master the link reflects the current state of the PFS. 1587If the PFS is a slave the link reflects the last completed snapshot, and the 1588contents of the link will change when the next snapshot is completed, and 1589so forth. 1590.Pp 1591The 1592.Nm 1593utility employs numerous safeties to reduce user foot-shooting. 1594The 1595.Cm mirror-copy 1596directive requires that the target be configured as a slave and that the 1597.Cm shared-uuid 1598field of the mirroring source and target match. 1599The 1600.Cm pfs-master 1601and 1602.Cm pfs-slave 1603directives require that the PFS softlink be created under the main 1604.Nm 1605filesystem mount. You may only access PFS softlinks via the main 1606.Nm 1607filesystem mount. 1608.Sh DOUBLE_BUFFER MODE 1609There is a limit to the number of vnodes the kernel can cache, and because 1610file buffers are associated with a vnode the related data cache can get 1611blown away when operating on large numbers of files even if the system has 1612sufficient memory to hold the file data. 1613.Pp 1614If you turn on 1615.Nm HAMMER Ns 's 1616double buffer mode by setting the 1617.Xr sysctl 8 1618node 1619.Va vfs.hammer.double_buffer 1620to 1 1621.Nm HAMMER 1622will cache file data via the block device and copy it into the per-file 1623buffers as needed. The data will be double-cached at least until the 1624buffer cache throws away the file buffer. 1625This mode is typically used in conjunction with 1626.Xr swapcache 8 1627when 1628.Va vm.swapcache.data_enable 1629is turned on in order to prevent unnecessary re-caching of file data 1630due to vnode recycling. 1631The swapcache will save the cached VM pages related to 1632.Nm HAMMER Ns 's 1633block 1634device (which doesn't recycle unless you umount the filesystem) instead 1635of the cached VM pages backing the file vnodes. 1636.Pp 1637Double buffering is normally desirable when working with large filesystems, 1638particularly when swapcache is used. 1639The swapcache can only back active VM objects, including the block device, 1640and large filesystems often have far more inodes than the kernel can support. 1641In addition, when using this mode, you may wish to reduce the 1642.Va kern.maxvnodes 1643setting for the system to force the system to do less caching of logical 1644file buffers and more caching of device buffers, since the device buffers 1645are backing the logical file buffers. 1646.Sh UPGRADE INSTRUCTIONS HAMMER V1 TO V2 1647This upgrade changes the way directory entries are stored. 1648It is possible to upgrade a V1 file system to V2 in place, but 1649directories created prior to the upgrade will continue to use 1650the old layout. 1651.Pp 1652Note that the slave mirroring code in the target kernel had bugs in 1653V1 which can create an incompatible root directory on the slave. 1654Do not mix a 1655.Nm HAMMER 1656master created after the upgrade with a 1657.Nm HAMMER 1658slave created prior to the upgrade. 1659.Pp 1660Any directories created after upgrading will use a new layout. 1661.Sh UPGRADE INSTRUCTIONS HAMMER V2 TO V3 1662This upgrade adds meta-data elements to the B-Tree. 1663It is possible to upgrade a V2 file system to V3 in place. 1664After issuing the upgrade be sure to run a 1665.Nm 1666.Cm cleanup 1667to perform post-upgrade tasks. 1668.Pp 1669After making this upgrade running a 1670.Nm 1671.Cm cleanup 1672will move the 1673.Pa <pfs>/snapshots 1674directory for each PFS mount into 1675.Pa /var/hammer/<pfs> . 1676A 1677.Nm HAMMER 1678root mount will migrate 1679.Pa /snapshots 1680into 1681.Pa /var/hammer/root . 1682Migration occurs only once and only if you have not specified 1683a snapshots directory in the PFS configuration. 1684If you have specified a snapshots directory in the PFS configuration no 1685automatic migration will occur. 1686.Pp 1687For slaves, if you desire, you can migrate your snapshots 1688config to the new location manually and then clear the 1689snapshot directory configuration in the slave PFS. 1690The new snapshots hierarchy is designed to work with 1691both master and slave PFSs equally well. 1692.Pp 1693In addition, the old config file will be moved to file system meta-data, 1694editable via the new 1695.Nm 1696.Cm viconfig 1697directive. 1698The old config file will be deleted. 1699Migration occurs only once. 1700.Pp 1701The V3 file system has new 1702.Cm snap* 1703directives for creating snapshots. 1704All snapshot directives, including the original, will create 1705meta-data entries for the snapshots and the pruning code will 1706automatically incorporate these entries into its list and 1707expire them the same way it expires softlinks. 1708If you by accident blow away your snapshot softlinks you can use the 1709.Cm snapls 1710directive to get a definitive list from the file system meta-data and 1711regenerate them from that list. 1712.Pp 1713.Em WARNING! 1714If you are using 1715.Nm 1716to backup file systems your scripts may be using the 1717.Cm synctid 1718directive to generate transaction ids. 1719This directive does not create a snapshot. 1720You will have to modify your scripts to use the 1721.Cm snapq 1722directive to generate the linkbuf for the softlink you create, or 1723use one of the other 1724.Cm snap* 1725directives. 1726The older 1727.Cm snapshot 1728directive will continue to work as expected and in V3 it will also 1729record the snapshot transaction id in file system meta-data. 1730You may also want to make use of the new 1731.Ar note 1732tag for the meta-data. 1733.Pp 1734.Em WARNING! 1735If you used to remove snapshot softlinks with 1736.Nm rm 1737you should probably start using the 1738.Cm snaprm 1739directive instead to also remove the related meta-data. 1740The pruning code scans the meta-data so just removing the 1741softlink is not sufficient. 1742.Sh UPGRADE INSTRUCTIONS HAMMER V3 TO V4 1743This upgrade changes undo/flush, giving faster sync. 1744It is possible to upgrade a V3 file system to V4 in place. 1745This upgrade reformats the UNDO/REDO FIFO (typically 1GB), 1746so upgrade might take a minute or two depending. 1747.Pp 1748Version 4 allows the UNDO/REDO FIFO to be flushed without also having 1749to flush the volume header, removing 2 of the 4 disk syncs typically 1750required for an 1751.Fn fsync 1752and removing 1 of the 2 disk syncs typically 1753required for a flush sequence. 1754Version 4 also implements the REDO log (see 1755.Sx FSYNC FLUSH MODES 1756below) which is capable 1757of fsync()ing with either one disk flush or zero disk flushes. 1758.Sh UPGRADE INSTRUCTIONS HAMMER V4 TO V5 1759This upgrade brings in deduplication support. 1760It is possible to upgrade a V4 file system to V5 in place. 1761Technically it makes the layer2 1762.Va bytes_free 1763field a signed value instead of unsigned, allowing it to go negative. 1764A version 5 filesystem is required for dedup operation. 1765.Sh UPGRADE INSTRUCTIONS HAMMER V5 TO V6 1766It is possible to upgrade a V5 file system to V6 in place. 1767.Sh FSYNC FLUSH MODES 1768.Nm HAMMER 1769implements five different fsync flush modes via the 1770.Va vfs.hammer.fsync_mode 1771sysctl, for 1772.Nm HAMMER 1773version 4+ file systems. 1774.Pp 1775As of 1776.Dx 2.6 1777fsync mode 3 is set by default. 1778REDO operation and recovery is enabled by default. 1779.Bl -tag -width indent 1780.It mode 0 1781Full synchronous fsync semantics without REDO. 1782.Pp 1783.Nm HAMMER 1784will not generate REDOs. 1785A 1786.Fn fsync 1787will completely sync 1788the data and meta-data and double-flush the FIFO, including 1789issuing two disk synchronization commands. 1790The data is guaranteed 1791to be on the media as of when 1792.Fn fsync 1793returns. 1794Needless to say, this is slow. 1795.It mode 1 1796Relaxed asynchronous fsync semantics without REDO. 1797.Pp 1798This mode works the same as mode 0 except the last disk synchronization 1799command is not issued. 1800It is faster than mode 0 but not even remotely 1801close to the speed you get with mode 2 or mode 3. 1802.Pp 1803Note that there is no chance of meta-data corruption when using this 1804mode, it simply means that the data you wrote and then 1805.Fn fsync Ns 'd 1806might not have made it to the media if the storage system crashes at a bad 1807time. 1808.It mode 2 1809Full synchronous fsync semantics using REDO. 1810NOTE: If not running a 1811.Nm HAMMER 1812version 4 filesystem or later mode 0 is silently used. 1813.Pp 1814.Nm HAMMER 1815will generate REDOs in the UNDO/REDO FIFO based on a heuristic. 1816If this is sufficient to satisfy the 1817.Fn fsync 1818operation the blocks will be written out and 1819.Nm HAMMER 1820will wait for the I/Os to complete, 1821and then followup with a disk sync command to guarantee the data 1822is on the media before returning. 1823This is slower than mode 3 and can result in significant disk or 1824SSDs overheads, though not as bad as mode 0 or mode 1. 1825.It mode 3 1826Relaxed asynchronous fsync semantics using REDO. 1827NOTE: If not running a 1828.Nm HAMMER 1829version 4 filesystem or later mode 1 is silently used. 1830.Pp 1831.Nm HAMMER 1832will generate REDOs in the UNDO/REDO FIFO based on a heuristic. 1833If this is sufficient to satisfy the 1834.Fn fsync 1835operation the blocks 1836will be written out and 1837.Nm HAMMER 1838will wait for the I/Os to complete, 1839but will 1840.Em NOT 1841issue a disk synchronization command. 1842.Pp 1843Note that there is no chance of meta-data corruption when using this 1844mode, it simply means that the data you wrote and then 1845.Fn fsync Ns 'd 1846might 1847not have made it to the media if the storage system crashes at a bad 1848time. 1849.Pp 1850This mode is the fastest production fsyncing mode available. 1851This mode is equivalent to how the UFS fsync in the 1852.Bx Ns s 1853operates. 1854.It mode 4 1855fsync is ignored. 1856.Pp 1857Calls to 1858.Fn fsync 1859will be ignored. 1860This mode is primarily designed 1861for testing and should not be used on a production system. 1862.El 1863.Sh RESTORING FROM A SNAPSHOT BACKUP 1864You restore a snapshot by copying it over to live, but there is a caveat. 1865The mtime and atime fields for files accessed via a snapshot is locked 1866to the ctime in order to keep the snapshot consistent, because neither 1867mtime nor atime changes roll any history. 1868.Pp 1869In order to avoid unnecessary copying it is recommended that you use 1870.Nm cpdup 1871.Fl VV 1872.Fl v 1873when doing the copyback. 1874Also make sure you traverse the snapshot softlink by appending a ".", 1875as in "<snapshotpath>/.", and you match up the directory properly. 1876.Sh RESTORING A PFS FROM A MIRROR 1877A PFS can be restored from a mirror with 1878.Cm mirror-copy . 1879.Cm config 1880data must be copied separately. 1881At last the PFS can be upgraded to master using 1882.Cm pfs-upgrade . 1883.Pp 1884It is not possible to restore the root PFS (PFS# 0) by using mirroring, 1885as the root PFS is always a master PFS. 1886A normal copy (e.g.\& using 1887.Xr cpdup 1 ) 1888must be done, ignoring history. 1889If history is important, old root PFS can me restored to a new PFS, and 1890important directories/files can be 1891.Nm null 1892mounted to the new PFS. 1893.Sh ENVIRONMENT 1894The following environment variables affect the execution of 1895.Nm : 1896.Bl -tag -width ".Ev EDITOR" 1897.It Ev EDITOR 1898The editor program specified in the variable 1899.Ev EDITOR 1900will be invoked instead of the default editor, which is 1901.Xr vi 1 . 1902.It Ev HAMMER_RSH 1903The command specified in the variable 1904.Ev HAMMER_RSH 1905will be used to initiate remote operations for the mirror-copy and 1906mirror-stream commands instead of the default command, which is 1907.Xr ssh 1 . 1908The program will be invoked via 1909.Xr execvp 3 1910using a typical 1911.Xr rsh 1 1912style 1913.Cm -l user host <remote-command> 1914command line. 1915.It Ev VISUAL 1916Same effect as 1917.Ev EDITOR 1918variable. 1919.El 1920.Sh FILES 1921.Bl -tag -width ".It Pa <fs>/var/slaves/<name>" -compact 1922.It Pa <pfs>/snapshots 1923default per PFS snapshots directory 1924.Nm ( HAMMER 1925VERSION 2-) 1926.It Pa /var/hammer/<pfs> 1927default per PFS snapshots directory (not root) 1928.Nm ( HAMMER 1929VERSION 3+) 1930.It Pa /var/hammer/root 1931default snapshots directory for root directory 1932.Nm ( HAMMER 1933VERSION 3+) 1934.It Pa <snapshots>/config 1935per PFS 1936.Nm 1937.Cm cleanup 1938configuration file 1939.Nm ( HAMMER 1940VERSION 2-) 1941.It Pa <fs>/var/slaves/<name> 1942recommended slave PFS snapshots directory 1943.Nm ( HAMMER 1944VERSION 2-) 1945.It Pa <fs>/pfs 1946recommended PFS directory 1947.El 1948.Sh EXIT STATUS 1949.Ex -std 1950.Sh SEE ALSO 1951.Xr ssh 1 , 1952.Xr undo 1 , 1953.Xr HAMMER 5 , 1954.Xr periodic.conf 5 , 1955.Xr loader 8 , 1956.Xr mount_hammer 8 , 1957.Xr mount_null 8 , 1958.Xr newfs_hammer 8 , 1959.Xr swapcache 8 , 1960.Xr sysctl 8 1961.Sh HISTORY 1962The 1963.Nm 1964utility first appeared in 1965.Dx 1.11 . 1966.Sh AUTHORS 1967.An Matthew Dillon Aq Mt dillon@backplane.com 1968