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 May 18, 2015 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.\" ==== history ==== 309.It Cm history Ns Oo Cm @ Ns Ar offset Ns Oo Cm \&, Ns Ar length Oc Oc Ar path ... 310Show the modification history for inode and data of 311.Nm HAMMER 312files. 313If 314.Ar offset 315is given history is shown for data block at given offset, 316otherwise history is shown for inode. 317If 318.Fl v 319is specified 320.Ar length 321data bytes at given offset are dumped for each version, 322default is 32. 323.Pp 324For each 325.Ar path 326this directive shows object id and sync status, 327and for each object version it shows transaction id and time stamp. 328Files has to exist for this directive to be applicable, 329to track inodes which has been deleted or renamed see 330.Xr undo 1 . 331.\" ==== blockmap ==== 332.It Cm blockmap 333Dump the blockmap for the file system. 334The 335.Nm HAMMER 336blockmap is two-layer 337blockmap representing the maximum possible file system size of 1 Exabyte. 338Needless to say the second layer is only present for blocks which exist. 339.Nm HAMMER Ns 's 340blockmap represents 8-Megabyte blocks, called big-blocks. 341Each big-block has an append 342point, a free byte count, and a typed zone id which allows content to be 343reverse engineered to some degree. 344.Pp 345In 346.Nm HAMMER 347allocations are essentially appended to a selected big-block using 348the append offset and deducted from the free byte count. 349When space is freed the free byte count is adjusted but 350.Nm HAMMER 351does not track holes in big-blocks for reallocation. 352A big-block must be completely freed, either 353through normal file system operations or through reblocking, before 354it can be reused. 355.Pp 356Data blocks can be shared by deducting the space used from the free byte 357count for each shared references. 358This means the free byte count can legally go negative. 359.Pp 360This command needs the 361.Fl f Ar blkdevs 362option. 363.\" ==== checkmap ==== 364.It Cm checkmap 365Check the blockmap allocation count. 366.Nm 367will scan the B-Tree, collect allocation information, and 368construct a blockmap in-memory. 369It will then check that blockmap against the on-disk blockmap. 370.Pp 371This command needs the 372.Fl f Ar blkdevs 373option. 374.\" ==== show ==== 375.It Cm show Op Ar localization Ns Op Cm \&: Ns Ar object_id 376Dump the B-Tree. 377By default this command will validate all B-Tree 378linkages and CRCs, including data CRCs, and will report the most verbose 379information it can dig up. 380Any errors will show up with a 381.Ql B 382in column 1 along with various 383other error flags. 384.Pp 385If you specify 386.Ar localization 387or 388.Ar localization Ns Cm \&: Ns Ar object_id 389the dump will 390search for the key printing nodes as it recurses down, and then 391will iterate forwards. 392These fields are specified in HEX. 393Note that the pfsid is the top 16 bits of the 32-bit localization 394field so PFS #1 would be 00010000. 395.Pp 396If you use 397.Fl q 398the command will report less information about the inode contents. 399.Pp 400If you use 401.Fl qq 402the command will not report the content of the inode or other typed 403data at all. 404.Pp 405If you use 406.Fl qqq 407the command will not report volume header information, big-block fill 408ratios, mirror transaction ids, or report or check data CRCs. 409B-Tree CRCs and linkages are still checked. 410.Pp 411This command needs the 412.Fl f Ar blkdevs 413option. 414.\" ==== show-undo ==== 415.It Cm show-undo 416.Nm ( HAMMER 417VERSION 4+) 418Dump the UNDO/REDO map. 419.Pp 420This command needs the 421.Fl f Ar blkdevs 422option. 423.\" .It Ar blockmap 424.\" Dump the B-Tree, record, large-data, and small-data blockmaps, showing 425.\" physical block assignments and free space percentages. 426.\" ==== ssh-remote ==== 427.It Cm ssh-remote Ar command Ar targetdir 428Used in a ssh authorized_keys line such as 429command="/sbin/hammer ssh-remote mirror-read /fubarmount" ... to allow 430mirror-read or mirror-write access to a particular subdirectory tree. 431This way you do not have to give shell access to the remote box. 432.Nm 433will obtain the original command line from the SSH_ORIGINAL_COMMAND 434environment variable, validate it against the restriction, and then 435re-exec hammer with the validated arguments. 436.Pp 437The remote hammer command does not allow the 438.Fl c 439or 440.Fl f 441options to be passed in. 442.\" ==== recover ==== 443.It Cm recover Ar targetdir 444Recover data from a corrupted 445.Nm HAMMER 446filesystem. 447This is a low level command which operates on the filesystem image and 448attempts to locate and recover files from a corrupted filesystem. 449The entire image is scanned linearly looking for B-Tree nodes. 450Any node 451found which passes its CRC test is scanned for file, inode, and directory 452fragments and the target directory is populated with the resulting data. 453files and directories in the target directory are initially named after 454the object id and are renamed as fragmentary information is processed. 455.Pp 456This command keeps track of filename/object_id translations and may eat a 457considerably amount of memory while operating. 458.Pp 459This command is literally the last line of defense when it comes to 460recovering data from a dead filesystem. 461.Pp 462This command needs the 463.Fl f Ar blkdevs 464option. 465.\" ==== namekey1 ==== 466.It Cm namekey1 Ar filename 467Generate a 468.Nm HAMMER 46964-bit directory hash for the specified file name, using 470the original directory hash algorithm in version 1 of the file system. 471The low 32 bits are used as an iterator for hash collisions and will be 472output as 0. 473.\" ==== namekey2 ==== 474.It Cm namekey2 Ar filename 475Generate a 476.Nm HAMMER 47764-bit directory hash for the specified file name, using 478the new directory hash algorithm in version 2 of the file system. 479The low 32 bits are still used as an iterator but will start out containing 480part of the hash key. 481.\" ==== namekey32 ==== 482.It Cm namekey32 Ar filename 483Generate the top 32 bits of a 484.Nm HAMMER 48564 bit directory hash for the specified file name. 486.\" ==== info ==== 487.It Cm info Ar dirpath ... 488Show extended information about all 489.Nm HAMMER 490file systems mounted in the system or the one mounted in 491.Ar dirpath 492when this argument is specified. 493.Pp 494The information is divided into sections: 495.Bl -tag -width indent 496.It Volume identification 497General information, like the label of the 498.Nm HAMMER 499filesystem, the number of volumes it contains, the FSID, and the 500.Nm HAMMER 501version being used. 502.It Big block information 503Big block statistics, such as total, used, reserved and free big blocks. 504.It Space information 505Information about space used on the filesystem. 506Currently total size, used, reserved and free space are displayed. 507.It PFS information 508Basic information about the PFSs currently present on a 509.Nm HAMMER 510filesystem. 511.Pp 512.Dq PFS ID 513is the ID of the PFS, with 0 being the root PFS. 514.Dq Snaps 515is the current snapshot count on the PFS. 516.Dq Mounted on 517displays the mount point of the PFS is currently mounted on (if any). 518.El 519.\" ==== cleanup ==== 520.It Cm cleanup Op Ar filesystem ... 521This is a meta-command which executes snapshot, prune, rebalance, dedup 522and reblock commands on the specified 523.Nm HAMMER 524file systems. 525If no 526.Ar filesystem 527is specified this command will clean-up all 528.Nm HAMMER 529file systems in use, including PFS's. 530To do this it will scan all 531.Nm HAMMER 532and 533.Nm null 534mounts, extract PFS id's, and clean-up each PFS found. 535.Pp 536This command will access a snapshots 537directory and a configuration file for each 538.Ar filesystem , 539creating them if necessary. 540.Bl -tag -width indent 541.It Nm HAMMER No version 2- 542The configuration file is 543.Pa config 544in the snapshots directory which defaults to 545.Pa <pfs>/snapshots . 546.It Nm HAMMER No version 3+ 547The configuration file is saved in file system meta-data, see 548.Nm 549.Cm config . 550The snapshots directory defaults to 551.Pa /var/hammer/<pfs> 552.Pa ( /var/hammer/root 553for root mount). 554.El 555.Pp 556The format of the configuration file is: 557.Bd -literal -offset indent 558snapshots <period> <retention-time> [any] 559prune <period> <max-runtime> 560rebalance <period> <max-runtime> 561dedup <period> <max-runtime> 562reblock <period> <max-runtime> 563recopy <period> <max-runtime> 564.Ed 565.Pp 566Defaults are: 567.Bd -literal -offset indent 568snapshots 1d 60d # 0d 0d for PFS /tmp, /var/tmp, /usr/obj 569prune 1d 5m 570rebalance 1d 5m 571dedup 1d 5m 572reblock 1d 5m 573recopy 30d 10m 574.Ed 575.Pp 576Time is given with a suffix of 577.Cm d , 578.Cm h , 579.Cm m 580or 581.Cm s 582meaning day, hour, minute and second. 583.Pp 584If the 585.Cm snapshots 586directive has a period of 0 and a retention time of 0 587then snapshot generation is disabled, removal of old snapshots are 588disabled, and prunes will use 589.Cm prune-everything . 590.Pp 591If the 592.Cm snapshots 593directive has a period of 0 but a non-zero retention time 594then this command will not create any new snapshots but will remove old 595snapshots it finds based on the retention time. 596This form should be 597used on PFS masters where you are generating your own snapshot softlinks 598manually and on PFS slaves when all you wish to do is prune away existing 599snapshots inherited via the mirroring stream. 600.Pp 601By default only snapshots in the form 602.Ql snap- Ns Ar yyyymmdd Ns Op - Ns Ar HHMM 603are processed. 604If the 605.Cm any 606directive is specified as a third argument on the 607.Cm snapshots 608config line then any softlink of the form 609.Ql *- Ns Ar yyyymmdd Ns Op - Ns Ar HHMM 610or 611.Ql *. Ns Ar yyyymmdd Ns Op - Ns Ar HHMM 612will be processed. 613.Pp 614A period of 0 for prune, rebalance, dedup, reblock or recopy disables the directive. 615A max-runtime of 0 means unlimited. 616.Pp 617If period hasn't passed since the previous 618.Cm cleanup 619run nothing is done. 620For example a day has passed when midnight is passed (localtime). 621If the 622.Fl F 623flag is given the period is ignored. 624By default, 625.Dx 626is set up to run 627.Nm Cm cleanup 628nightly via 629.Xr periodic 8 . 630.Pp 631The default configuration file will create a daily snapshot, do a daily 632pruning, rebalancing, deduping and reblocking run and a monthly recopy run. 633Reblocking is defragmentation with a level of 95%, 634and recopy is full defragmentation. 635.Pp 636By default prune, dedup and rebalance operations are time limited to 5 minutes, 637and reblock operations to a bit over 5 minutes, 638and recopy operations to a bit over 10 minutes. 639Reblocking and recopy runs are each broken down into four separate functions: 640btree, inodes, dirs and data. 641Each function is time limited to the time given in the configuration file, 642but the btree, inodes and dirs functions usually does not take very long time, 643full defragmentation is always used for these three functions. 644Also note that this directive will by default disable snapshots on 645the following PFS's: 646.Pa /tmp , 647.Pa /var/tmp 648and 649.Pa /usr/obj . 650.Pp 651The defaults may be adjusted by modifying the configuration file. 652The pruning and reblocking commands automatically maintain a cyclefile 653for incremental operation. 654If you interrupt (^C) the program the cyclefile will be updated, 655but a sub-command 656may continue to run in the background for a few seconds until the 657.Nm HAMMER 658ioctl detects the interrupt. 659The 660.Cm snapshots 661PFS option can be set to use another location for the snapshots directory. 662.Pp 663Work on this command is still in progress. 664Expected additions: 665An ability to remove snapshots dynamically as the 666file system becomes full. 667.\" ==== abort-cleanup ==== 668.It Cm abort-cleanup 669This command will terminate all active 670.Cm cleanup 671processes. 672.\" ==== config ==== 673.It Cm config Op Ar filesystem Op Ar configfile 674.Nm ( HAMMER 675VERSION 3+) 676Show or change configuration for 677.Ar filesystem . 678If zero or one arguments are specified this function dumps the current 679configuration file to stdout. 680Zero arguments specifies the PFS containing the current directory. 681This configuration file is stored in file system meta-data. 682If two arguments are specified this function installs a new config file. 683.Pp 684In 685.Nm HAMMER 686versions less than 3 the configuration file is by default stored in 687.Pa <pfs>/snapshots/config , 688but in all later versions the configuration file is stored in file system 689meta-data. 690.\" ==== viconfig ==== 691.It Cm viconfig Op Ar filesystem 692.Nm ( HAMMER 693VERSION 3+) 694Edit the configuration file and reinstall into file system meta-data when done. 695Zero arguments specifies the PFS containing the current directory. 696.\" ==== volume-add ==== 697.It Cm volume-add Ar device Ar filesystem 698Add volume 699.Ar device 700to 701.Ar filesystem . 702This will format 703.Ar device 704and add all of its space to 705.Ar filesystem . 706A 707.Nm HAMMER 708file system can use up to 256 volumes. 709.Pp 710.Em NOTE! 711All existing data contained on 712.Ar device 713will be destroyed by this operation! 714If 715.Ar device 716contains a valid 717.Nm HAMMER 718file system, formatting will be denied. 719You can overcome this sanity check by using 720.Xr dd 1 721to erase the beginning sectors of the device. 722.Pp 723Remember that you have to specify 724.Ar device , 725together with any other device that make up the file system, 726colon-separated to 727.Pa /etc/fstab 728and 729.Xr mount_hammer 8 . 730If 731.Ar filesystem 732is root file system, also remember to add 733.Ar device 734to 735.Va vfs.root.mountfrom 736in 737.Pa /boot/loader.conf , 738see 739.Xr loader 8 . 740.\" ==== volume-del ==== 741.It Cm volume-del Ar device Ar filesystem 742Remove volume 743.Ar device 744from 745.Ar filesystem . 746.Pp 747Remember that you have to remove 748.Ar device 749from the colon-separated list in 750.Pa /etc/fstab 751and 752.Xr mount_hammer 8 . 753If 754.Ar filesystem 755is root file system, also remember to remove 756.Ar device 757from 758.Va vfs.root.mountfrom 759in 760.Pa /boot/loader.conf , 761see 762.Xr loader 8 . 763.\" ==== volume-list ==== 764.It Cm volume-list Ar filesystem 765List the volumes that make up 766.Ar filesystem . 767.\" ==== snapshot ==== 768.It Cm snapshot Oo Ar filesystem Oc Ar snapshot-dir 769.It Cm snapshot Ar filesystem Ar snapshot-dir Op Ar note 770Take a snapshot of the file system either explicitly given by 771.Ar filesystem 772or implicitly derived from the 773.Ar snapshot-dir 774argument and creates a symlink in the directory provided by 775.Ar snapshot-dir 776pointing to the snapshot. 777If 778.Ar snapshot-dir 779is not a directory, it is assumed to be a format string passed to 780.Xr strftime 3 781with the current time as parameter. 782If 783.Ar snapshot-dir 784refers to an existing directory, a default format string of 785.Ql snap-%Y%m%d-%H%M 786is assumed and used as name for the newly created symlink. 787.Pp 788Snapshot is a per PFS operation, so each PFS in a 789.Nm HAMMER 790file system have to be snapshot separately. 791.Pp 792Example, assuming that 793.Pa /mysnapshots 794is on file system 795.Pa / 796and that 797.Pa /obj 798and 799.Pa /usr 800are file systems on their own, the following invocations: 801.Bd -literal -offset indent 802hammer snapshot /mysnapshots 803 804hammer snapshot /mysnapshots/%Y-%m-%d 805 806hammer snapshot /obj /mysnapshots/obj-%Y-%m-%d 807 808hammer snapshot /usr /my/snaps/usr "note" 809.Ed 810.Pp 811Would create symlinks similar to: 812.Bd -literal -offset indent 813/mysnapshots/snap-20080627-1210 -> /@@0x10d2cd05b7270d16 814 815/mysnapshots/2008-06-27 -> /@@0x10d2cd05b7270d16 816 817/mysnapshots/obj-2008-06-27 -> /obj@@0x10d2cd05b7270d16 818 819/my/snaps/usr/snap-20080627-1210 -> /usr@@0x10d2cd05b7270d16 820.Ed 821.Pp 822When run on a 823.Nm HAMMER 824version 3+ file system the snapshot is also recorded in file system meta-data 825along with the optional 826.Ar note . 827See the 828.Cm snapls 829directive. 830.\" ==== snap* ==== 831.It Cm snap Ar path Op Ar note 832.Nm ( HAMMER 833VERSION 3+) 834Create a snapshot for the PFS containing 835.Ar path 836and create a snapshot softlink. 837If the path specified is a 838directory a standard snapshot softlink will be created in the directory. 839The snapshot softlink points to the base of the mounted PFS. 840.It Cm snaplo Ar path Op Ar note 841.Nm ( HAMMER 842VERSION 3+) 843Create a snapshot for the PFS containing 844.Ar path 845and create a snapshot softlink. 846If the path specified is a 847directory a standard snapshot softlink will be created in the directory. 848The snapshot softlink points into the directory it is contained in. 849.It Cm snapq Ar dir Op Ar note 850.Nm ( HAMMER 851VERSION 3+) 852Create a snapshot for the PFS containing the specified directory but do 853not create a softlink. 854Instead output a path which can be used to access 855the directory via the snapshot. 856.Pp 857An absolute or relative path may be specified. 858The path will be used as-is as a prefix in the path output to stdout. 859As with the other 860snap and snapshot directives the snapshot transaction id will be registered 861in the file system meta-data. 862.It Cm snaprm Ar path Ar ... 863.It Cm snaprm Ar transaction_id Ar ... 864.It Cm snaprm Ar filesystem Ar transaction_id Ar ... 865.Nm ( HAMMER 866VERSION 3+) 867Remove a snapshot given its softlink or transaction id. 868If specifying a transaction id 869the snapshot is removed from file system meta-data but you are responsible 870for removing any related softlinks. 871.Pp 872If a softlink path is specified the filesystem and transaction id 873is derived from the contents of the softlink. 874If just a transaction id is specified it is assumed to be a snapshot in the 875.Nm HAMMER 876filesystem you are currently chdir'd into. 877You can also specify the filesystem and transaction id explicitly. 878.It Cm snapls Op Ar path ... 879.Nm ( HAMMER 880VERSION 3+) 881Dump the snapshot meta-data for PFSs containing each 882.Ar path 883listing all available snapshots and their notes. 884If no arguments are specified snapshots for the PFS containing the 885current directory are listed. 886This is the definitive list of snapshots for the file system. 887.\" ==== prune ==== 888.It Cm prune Ar softlink-dir 889Prune the file system based on previously created snapshot softlinks. 890Pruning is the act of deleting file system history. 891The 892.Cm prune 893command will delete file system history such that 894the file system state is retained for the given snapshots, 895and all history after the latest snapshot. 896By setting the per PFS parameter 897.Cm prune-min , 898history is guaranteed to be saved at least this time interval. 899All other history is deleted. 900.Pp 901The target directory is expected to contain softlinks pointing to 902snapshots of the file systems you wish to retain. 903The directory is scanned non-recursively and the mount points and 904transaction ids stored in the softlinks are extracted and sorted. 905The file system is then explicitly pruned according to what is found. 906Cleaning out portions of the file system is as simple as removing a 907snapshot softlink and then running the 908.Cm prune 909command. 910.Pp 911As a safety measure pruning only occurs if one or more softlinks are found 912containing the 913.Ql @@ 914snapshot id extension. 915Currently the scanned softlink directory must contain softlinks pointing 916to a single 917.Nm HAMMER 918mount. 919The softlinks may specify absolute or relative paths. 920Softlinks must use 20-character 921.Ql @@0x%016llx 922transaction ids, as might be returned from 923.Nm Cm synctid Ar filesystem . 924.Pp 925Pruning is a per PFS operation, so each PFS in a 926.Nm HAMMER 927file system have to be pruned separately. 928.Pp 929Note that pruning a file system may not immediately free-up space, 930though typically some space will be freed if a large number of records are 931pruned out. 932The file system must be reblocked to completely recover all available space. 933.Pp 934Example, lets say your that you didn't set 935.Cm prune-min , 936and snapshot directory contains the following links: 937.Bd -literal -offset indent 938lrwxr-xr-x 1 root wheel 29 May 31 17:57 snap1 -> 939/usr/obj/@@0x10d2cd05b7270d16 940 941lrwxr-xr-x 1 root wheel 29 May 31 17:58 snap2 -> 942/usr/obj/@@0x10d2cd13f3fde98f 943 944lrwxr-xr-x 1 root wheel 29 May 31 17:59 snap3 -> 945/usr/obj/@@0x10d2cd222adee364 946.Ed 947.Pp 948If you were to run the 949.Cm prune 950command on this directory, then the 951.Nm HAMMER 952.Pa /usr/obj 953mount will be pruned to retain the above three snapshots. 954In addition, history for modifications made to the file system older than 955the oldest snapshot will be destroyed and history for potentially fine-grained 956modifications made to the file system more recently than the most recent 957snapshot will be retained. 958.Pp 959If you then delete the 960.Pa snap2 961softlink and rerun the 962.Cm prune 963command, 964history for modifications pertaining to that snapshot would be destroyed. 965.Pp 966In 967.Nm HAMMER 968file system versions 3+ this command also scans the snapshots stored 969in the file system meta-data and includes them in the prune. 970.\" ==== prune-everything ==== 971.It Cm prune-everything Ar filesystem 972Remove all historical records from 973.Ar filesystem . 974Use this directive with caution on PFSs where you intend to use history. 975.Pp 976This command does not remove snapshot softlinks but will delete all 977snapshots recorded in file system meta-data (for file system version 3+). 978The user is responsible for deleting any softlinks. 979.Pp 980Pruning is a per PFS operation, so each PFS in a 981.Nm HAMMER 982file system have to be pruned separately. 983.\" ==== rebalance ==== 984.It Cm rebalance Ar filesystem Op Ar saturation_percentage 985Rebalance the B-Tree, nodes with small number of 986elements will be combined and element counts will be smoothed out 987between nodes. 988.Pp 989The saturation percentage is between 50% and 100%. 990The default is 85% (the 991.Sq % 992suffix is not needed). 993.Pp 994Rebalancing is a per PFS operation, so each PFS in a 995.Nm HAMMER 996file system have to be rebalanced separately. 997.\" ==== dedup ==== 998.It Cm dedup Ar filesystem 999.Nm ( HAMMER 1000VERSION 5+) 1001Perform offline (post-process) deduplication. 1002Deduplication occurs at 1003the block level, currently only data blocks of the same size can be 1004deduped, metadata blocks can not. 1005The hash function used for comparing 1006data blocks is CRC-32 (CRCs are computed anyways as part of 1007.Nm HAMMER 1008data integrity features, so there's no additional overhead). 1009Since CRC is a weak hash function a byte-by-byte comparison is done 1010before actual deduping. 1011In case of a CRC collision (two data blocks have the same CRC 1012but different contents) the checksum is upgraded to SHA-256. 1013.Pp 1014Currently 1015.Nm HAMMER 1016reblocker may partially blow up (re-expand) dedup (reblocker's normal 1017operation is to reallocate every record, so it's possible for deduped 1018blocks to be re-expanded back). 1019.Pp 1020Deduplication is a per PFS operation, so each PFS in a 1021.Nm HAMMER 1022file system have to be deduped separately. 1023This also 1024means that if you have duplicated data in two different PFSs that data 1025won't be deduped, however the addition of such feature is planned. 1026.Pp 1027The 1028.Fl m Ar memlimit 1029option should be used to limit memory use during the dedup run if the 1030default 1G limit is too much for the machine. 1031.\" ==== dedup-simulate ==== 1032.It Cm dedup-simulate Ar filesystem 1033Shows potential space savings (simulated dedup ratio) one can get after 1034running 1035.Cm dedup 1036command. 1037If the estimated dedup ratio is greater than 1.00 you will see 1038dedup space savings. 1039Remember that this is an estimated number, in 1040practice real dedup ratio will be slightly smaller because of 1041.Nm HAMMER 1042bigblock underflows, B-Tree locking issues and other factors. 1043.Pp 1044Note that deduplication currently works only on bulk data so if you 1045try to run 1046.Cm dedup-simulate 1047or 1048.Cm dedup 1049commands on a PFS that contains metadata only (directory entries, 1050softlinks) you will get a 0.00 dedup ratio. 1051.Pp 1052The 1053.Fl m Ar memlimit 1054option should be used to limit memory use during the dedup run if the 1055default 1G limit is too much for the machine. 1056.\" ==== reblock* ==== 1057.It Cm reblock Ar filesystem Op Ar fill_percentage 1058.It Cm reblock-btree Ar filesystem Op Ar fill_percentage 1059.It Cm reblock-inodes Ar filesystem Op Ar fill_percentage 1060.It Cm reblock-dirs Ar filesystem Op Ar fill_percentage 1061.It Cm reblock-data Ar filesystem Op Ar fill_percentage 1062Attempt to defragment and free space for reuse by reblocking a live 1063.Nm HAMMER 1064file system. 1065Big-blocks cannot be reused by 1066.Nm HAMMER 1067until they are completely free. 1068This command also has the effect of reordering all elements, effectively 1069defragmenting the file system. 1070.Pp 1071The default fill percentage is 100% and will cause the file system to be 1072completely defragmented. 1073All specified element types will be reallocated and rewritten. 1074If you wish to quickly free up space instead try specifying 1075a smaller fill percentage, such as 90% or 80% (the 1076.Sq % 1077suffix is not needed). 1078.Pp 1079Since this command may rewrite the entire contents of the disk it is 1080best to do it incrementally from a 1081.Xr cron 8 1082job along with the 1083.Fl c Ar cyclefile 1084and 1085.Fl t Ar seconds 1086options to limit the run time. 1087The file system would thus be defragmented over long period of time. 1088.Pp 1089It is recommended that separate invocations be used for each data type. 1090B-Tree nodes, inodes, and directories are typically the most important 1091elements needing defragmentation. 1092Data can be defragmented over a longer period of time. 1093.Pp 1094Reblocking is a per PFS operation, so each PFS in a 1095.Nm HAMMER 1096file system have to be reblocked separately. 1097.\" ==== pfs-status ==== 1098.It Cm pfs-status Ar dirpath ... 1099Retrieve the mirroring configuration parameters for the specified 1100.Nm HAMMER 1101file systems or pseudo-filesystems (PFS's). 1102.\" ==== pfs-master ==== 1103.It Cm pfs-master Ar dirpath Op Ar options 1104Create a pseudo-filesystem (PFS) inside a 1105.Nm HAMMER 1106file system. 1107Up to 65536 PFSs can be created. 1108Each PFS uses an independent inode numbering space making it suitable 1109for replication. 1110.Pp 1111The 1112.Cm pfs-master 1113directive creates a PFS that you can read, write, and use as a mirroring 1114source. 1115.Pp 1116A PFS can only be truly destroyed with the 1117.Cm pfs-destroy 1118directive. 1119Removing the softlink will not destroy the underlying PFS. 1120.Pp 1121A PFS can only be created in the root PFS (PFS# 0), 1122not in a PFS created by 1123.Cm pfs-master 1124or 1125.Cm pfs-slave 1126(PFS# >0). 1127.Pp 1128It is recommended that 1129.Ar dirpath 1130is of the form 1131.Pa <fs>/pfs/<name> 1132(i.e.\& located in 1133.Pa pfs 1134directory at root of 1135.Nm HAMMER 1136file system). 1137.Pp 1138It is recommended to use a 1139.Nm null 1140mount to access a PFS, except for root PFS, for more information see 1141.Xr HAMMER 5 . 1142.\" ==== pfs-slave ==== 1143.It Cm pfs-slave Ar dirpath Op Ar options 1144Create a pseudo-filesystem (PFS) inside a 1145.Nm HAMMER 1146file system. 1147Up to 65536 PFSs can be created. 1148Each PFS uses an independent inode numbering space making it suitable 1149for replication. 1150.Pp 1151The 1152.Cm pfs-slave 1153directive creates a PFS that you can use as a mirroring source or target. 1154You will not be able to access a slave PFS until you have completed the 1155first mirroring operation with it as the target (its root directory will 1156not exist until then). 1157.Pp 1158Access to the pfs-slave via the special softlink, as described in the 1159.Sx PSEUDO-FILESYSTEM (PFS) NOTES 1160below, allows 1161.Nm HAMMER 1162to 1163dynamically modify the snapshot transaction id by returning a dynamic result 1164from 1165.Xr readlink 2 1166calls. 1167.Pp 1168A PFS can only be truly destroyed with the 1169.Cm pfs-destroy 1170directive. 1171Removing the softlink will not destroy the underlying PFS. 1172.Pp 1173A PFS can only be created in the root PFS (PFS# 0), 1174not in a PFS created by 1175.Cm pfs-master 1176or 1177.Cm pfs-slave 1178(PFS# >0). 1179.Pp 1180It is recommended that 1181.Ar dirpath 1182is of the form 1183.Pa <fs>/pfs/<name> 1184(i.e.\& located in 1185.Pa pfs 1186directory at root of 1187.Nm HAMMER 1188file system). 1189.Pp 1190It is recommended to use a 1191.Nm null 1192mount to access a PFS, except for root PFS, for more information see 1193.Xr HAMMER 5 . 1194.\" ==== pfs-update ==== 1195.It Cm pfs-update Ar dirpath Op Ar options 1196Update the configuration parameters for an existing 1197.Nm HAMMER 1198file system or pseudo-filesystem. 1199Options that may be specified: 1200.Bl -tag -width indent 1201.It Cm sync-beg-tid= Ns Ar 0x16llx 1202This is the automatic snapshot access starting transaction id for 1203mirroring slaves. 1204This parameter is normally updated automatically by the 1205.Cm mirror-write 1206directive. 1207.Pp 1208It is important to note that accessing a mirroring slave 1209with a transaction id greater than the last fully synchronized transaction 1210id can result in an unreliable snapshot since you will be accessing 1211data that is still undergoing synchronization. 1212.Pp 1213Manually modifying this field is dangerous and can result in a broken mirror. 1214.It Cm sync-end-tid= Ns Ar 0x16llx 1215This is the current synchronization point for mirroring slaves. 1216This parameter is normally updated automatically by the 1217.Cm mirror-write 1218directive. 1219.Pp 1220Manually modifying this field is dangerous and can result in a broken mirror. 1221.It Cm shared-uuid= Ns Ar uuid 1222Set the shared UUID for this file system. 1223All mirrors must have the same shared UUID. 1224For safety purposes the 1225.Cm mirror-write 1226directives will refuse to operate on a target with a different shared UUID. 1227.Pp 1228Changing the shared UUID on an existing, non-empty mirroring target, 1229including an empty but not completely pruned target, 1230can lead to corruption of the mirroring target. 1231.It Cm unique-uuid= Ns Ar uuid 1232Set the unique UUID for this file system. 1233This UUID should not be used anywhere else, 1234even on exact copies of the file system. 1235.It Cm label= Ns Ar string 1236Set a descriptive label for this file system. 1237.It Cm snapshots= Ns Ar string 1238Specify the snapshots directory which 1239.Nm 1240.Cm cleanup 1241will use to manage this PFS. 1242.Bl -tag -width indent 1243.It Nm HAMMER No version 2- 1244The snapshots directory does not need to be configured for 1245PFS masters and will default to 1246.Pa <pfs>/snapshots . 1247.Pp 1248PFS slaves are mirroring slaves so you cannot configure a snapshots 1249directory on the slave itself to be managed by the slave's machine. 1250In fact, the slave will likely have a 1251.Pa snapshots 1252sub-directory mirrored 1253from the master, but that directory contains the configuration the master 1254is using for its copy of the file system, not the configuration that we 1255want to use for our slave. 1256.Pp 1257It is recommended that 1258.Pa <fs>/var/slaves/<name> 1259be configured for a PFS slave, where 1260.Pa <fs> 1261is the base 1262.Nm HAMMER 1263file system, and 1264.Pa <name> 1265is an appropriate label. 1266.It Nm HAMMER No version 3+ 1267The snapshots directory does not need to be configured for PFS masters or 1268slaves. 1269The snapshots directory defaults to 1270.Pa /var/hammer/<pfs> 1271.Pa ( /var/hammer/root 1272for root mount). 1273.El 1274.Pp 1275You can control snapshot retention on your slave independent of the master. 1276.It Cm snapshots-clear 1277Zero out the 1278.Cm snapshots 1279directory path for this PFS. 1280.It Cm prune-min= Ns Ar N Ns Cm d 1281.It Cm prune-min= Ns Oo Ar N Ns Cm d/ Oc Ns \ 1282Ar hh Ns Op Cm \&: Ns Ar mm Ns Op Cm \&: Ns Ar ss 1283Set the minimum fine-grained data retention period. 1284.Nm HAMMER 1285always retains fine-grained history up to the most recent snapshot. 1286You can extend the retention period further by specifying a non-zero 1287pruning minimum. 1288Any snapshot softlinks within the retention period are ignored 1289for the purposes of pruning (i.e.\& the fine grained history is retained). 1290Number of days, hours, minutes and seconds are given as 1291.Ar N , hh , mm 1292and 1293.Ar ss . 1294.Pp 1295Because the transaction id in the snapshot softlink cannot be used 1296to calculate a timestamp, 1297.Nm HAMMER 1298uses the earlier of the 1299.Fa st_ctime 1300or 1301.Fa st_mtime 1302field of the softlink to 1303determine which snapshots fall within the retention period. 1304Users must be sure to retain one of these two fields when manipulating 1305the softlink. 1306.El 1307.\" ==== pfs-upgrade ==== 1308.It Cm pfs-upgrade Ar dirpath 1309Upgrade a PFS from slave to master operation. 1310The PFS will be rolled back to the current end synchronization transaction id 1311(removing any partial synchronizations), and will then become writable. 1312.Pp 1313.Em WARNING! 1314.Nm HAMMER 1315currently supports only single masters and using 1316this command can easily result in file system corruption 1317if you don't know what you are doing. 1318.Pp 1319This directive will refuse to run if any programs have open descriptors 1320in the PFS, including programs chdir'd into the PFS. 1321.\" ==== pfs-downgrade ==== 1322.It Cm pfs-downgrade Ar dirpath 1323Downgrade a master PFS from master to slave operation. 1324The PFS becomes read-only and access will be locked to its 1325.Cm sync-end-tid . 1326.Pp 1327This directive will refuse to run if any programs have open descriptors 1328in the PFS, including programs chdir'd into the PFS. 1329.\" ==== pfs-destroy ==== 1330.It Cm pfs-destroy Ar dirpath 1331This permanently destroys a PFS. 1332.Pp 1333This directive will refuse to run if any programs have open descriptors 1334in the PFS, including programs chdir'd into the PFS. 1335As safety measure the 1336.Fl y 1337flag have no effect on this directive. 1338.\" ==== mirror-read ==== 1339.It Cm mirror-read Ar filesystem Op Ar begin-tid 1340Generate a mirroring stream to stdout. 1341The stream ends when the transaction id space has been exhausted. 1342.Ar filesystem 1343may be a master or slave PFS. 1344.\" ==== mirror-read-stream ==== 1345.It Cm mirror-read-stream Ar filesystem Op Ar begin-tid 1346Generate a mirroring stream to stdout. 1347Upon completion the stream is paused until new data is synced to the 1348.Ar filesystem , 1349then resumed. 1350Operation continues until the pipe is broken. 1351See the 1352.Cm mirror-stream 1353command for more details. 1354.\" ==== mirror-write ==== 1355.It Cm mirror-write Ar filesystem 1356Take a mirroring stream on stdin. 1357.Ar filesystem 1358must be a slave PFS. 1359.Pp 1360This command will fail if the 1361.Cm shared-uuid 1362configuration field for the two file systems do not match. 1363See the 1364.Cm mirror-copy 1365command for more details. 1366.Pp 1367If the target PFS does not exist this command will ask you whether 1368you want to create a compatible PFS slave for the target or not. 1369.\" ==== mirror-dump ==== 1370.It Ar mirror-dump Ar [header] 1371A 1372.Cm mirror-read 1373can be piped into a 1374.Cm mirror-dump 1375to dump an ASCII representation of the mirroring stream. 1376If the keyword 1377.Ar header 1378is specified, only the header information is shown. 1379.\" ==== mirror-copy ==== 1380.\".It Cm mirror-copy Ar [[user@]host:]filesystem [[user@]host:]filesystem 1381.It Cm mirror-copy \ 1382Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \ 1383Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem 1384This is a shortcut which pipes a 1385.Cm mirror-read 1386command to a 1387.Cm mirror-write 1388command. 1389If a remote host specification is made the program forks a 1390.Xr ssh 1 1391(or other program as specified by the 1392.Ev HAMMER_RSH 1393environment variable) and execs the 1394.Cm mirror-read 1395and/or 1396.Cm mirror-write 1397on the appropriate host. 1398The source may be a master or slave PFS, and the target must be a slave PFS. 1399.Pp 1400This command also establishes full duplex communication and turns on 1401the 2-way protocol feature 1402.Fl ( 2 ) 1403which automatically negotiates transaction id 1404ranges without having to use a cyclefile. 1405If the operation completes successfully the target PFS's 1406.Cm sync-end-tid 1407will be updated. 1408Note that you must re-chdir into the target PFS to see the updated information. 1409If you do not you will still be in the previous snapshot. 1410.Pp 1411If the target PFS does not exist this command will ask you whether 1412you want to create a compatible PFS slave for the target or not. 1413.\" ==== mirror-stream ==== 1414.\".It Cm mirror-stream Ar [[user@]host:]filesystem [[user@]host:]filesystem 1415.It Cm mirror-stream \ 1416Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \ 1417Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem 1418This is a shortcut which pipes a 1419.Cm mirror-read-stream 1420command to a 1421.Cm mirror-write 1422command. 1423This command works similarly to 1424.Cm mirror-copy 1425but does not exit after the initial mirroring completes. 1426The mirroring operation will resume as changes continue to be made to the 1427source. 1428The command is commonly used with 1429.Fl i Ar delay 1430and 1431.Fl b Ar bandwidth 1432options to keep the mirroring target in sync with the source on a continuing 1433basis. 1434.Pp 1435If the pipe is broken the command will automatically retry after sleeping 1436for a short while. 1437The time slept will be 15 seconds plus the time given in the 1438.Fl i 1439option. 1440.Pp 1441This command also detects the initial-mirroring case and spends some 1442time scanning the B-Tree to find good break points, allowing the initial 1443bulk mirroring operation to be broken down into 4GB pieces. 1444This means that the user can kill and restart the operation and it will 1445not have to start from scratch once it has gotten past the first chunk. 1446The 1447.Fl S 1448option may be used to change the size of pieces and the 1449.Fl B 1450option may be used to disable this feature and perform an initial bulk 1451transfer instead. 1452.\" ==== version ==== 1453.It Cm version Ar filesystem 1454This command returns the 1455.Nm HAMMER 1456file system version for the specified 1457.Ar filesystem 1458as well as the range of versions supported in the kernel. 1459The 1460.Fl q 1461option may be used to remove the summary at the end. 1462.\" ==== version-upgrade ==== 1463.It Cm version-upgrade Ar filesystem Ar version Op Cm force 1464Upgrade the 1465.Nm HAMMER 1466.Ar filesystem 1467to the specified 1468.Ar version . 1469Once upgraded a file system may not be downgraded. 1470If you wish to upgrade a file system to a version greater or equal to the 1471work-in-progress (WIP) version number you must specify the 1472.Cm force 1473directive. 1474Use of WIP versions should be relegated to testing and may require wiping 1475the file system as development progresses, even though the WIP version might 1476not change. 1477.Pp 1478.Em NOTE! 1479This command operates on the entire 1480.Nm HAMMER 1481file system and is not a per PFS operation. 1482All PFS's will be affected. 1483.Bl -tag -width indent 1484.It 1 1485.Dx 2.0 1486default version, first 1487.Nm HAMMER 1488release. 1489.It 2 1490.Dx 2.3 . 1491New directory entry layout. 1492This version is using a new directory hash key. 1493.It 3 1494.Dx 2.5 . 1495New snapshot management, using file system meta-data for saving 1496configuration file and snapshots (transaction ids etc.). 1497Also default snapshots directory has changed. 1498.It 4 1499.Dx 2.6 1500default version. 1501New undo/redo/flush, giving 1502.Nm HAMMER 1503a much faster sync and fsync. 1504.It 5 1505.Dx 2.9 . 1506Deduplication support. 1507.It 6 1508.Dx 2.9 . 1509Directory hash ALG1. 1510Tends to maintain inode number / directory name entry ordering better 1511for files after minor renaming. 1512.El 1513.El 1514.Sh PSEUDO-FILESYSTEM (PFS) NOTES 1515The root of a PFS is not hooked into the primary 1516.Nm HAMMER 1517file system as a directory. 1518Instead, 1519.Nm HAMMER 1520creates a special softlink called 1521.Ql @@PFS%05d 1522(exactly 10 characters long) in the primary 1523.Nm HAMMER 1524file system. 1525.Nm HAMMER 1526then modifies the contents of the softlink as read by 1527.Xr readlink 2 , 1528and thus what you see with an 1529.Nm ls 1530command or if you were to 1531.Nm cd 1532into the link. 1533If the PFS is a master the link reflects the current state of the PFS. 1534If the PFS is a slave the link reflects the last completed snapshot, and the 1535contents of the link will change when the next snapshot is completed, and 1536so forth. 1537.Pp 1538The 1539.Nm 1540utility employs numerous safeties to reduce user foot-shooting. 1541The 1542.Cm mirror-copy 1543directive requires that the target be configured as a slave and that the 1544.Cm shared-uuid 1545field of the mirroring source and target match. 1546.Sh DOUBLE_BUFFER MODE 1547There is a limit to the number of vnodes the kernel can cache, and because 1548file buffers are associated with a vnode the related data cache can get 1549blown away when operating on large numbers of files even if the system has 1550sufficient memory to hold the file data. 1551.Pp 1552If you turn on 1553.Nm HAMMER Ns 's 1554double buffer mode by setting the 1555.Xr sysctl 8 1556node 1557.Va vfs.hammer.double_buffer 1558to 1 1559.Nm HAMMER 1560will cache file data via the block device and copy it into the per-file 1561buffers as needed. The data will be double-cached at least until the 1562buffer cache throws away the file buffer. 1563This mode is typically used in conjunction with 1564.Xr swapcache 8 1565when 1566.Va vm.swapcache.data_enable 1567is turned on in order to prevent unnecessary re-caching of file data 1568due to vnode recycling. 1569The swapcache will save the cached VM pages related to 1570.Nm HAMMER Ns 's 1571block 1572device (which doesn't recycle unless you umount the filesystem) instead 1573of the cached VM pages backing the file vnodes. 1574.\".Pp 1575.\"Double buffering should also be turned on if live dedup is enabled via 1576.\"Va vfs.hammer.live_dedup . 1577.\"This is because the live dedup must validate the contents of a potential 1578.\"duplicate file block and it must run through the block device to do that 1579.\"and not the file vnode. 1580.\"If double buffering is not enabled then live dedup will create extra disk 1581.\"reads to validate potential data duplicates. 1582.Sh UPGRADE INSTRUCTIONS HAMMER V1 TO V2 1583This upgrade changes the way directory entries are stored. 1584It is possible to upgrade a V1 file system to V2 in place, but 1585directories created prior to the upgrade will continue to use 1586the old layout. 1587.Pp 1588Note that the slave mirroring code in the target kernel had bugs in 1589V1 which can create an incompatible root directory on the slave. 1590Do not mix a 1591.Nm HAMMER 1592master created after the upgrade with a 1593.Nm HAMMER 1594slave created prior to the upgrade. 1595.Pp 1596Any directories created after upgrading will use a new layout. 1597.Sh UPGRADE INSTRUCTIONS HAMMER V2 TO V3 1598This upgrade adds meta-data elements to the B-Tree. 1599It is possible to upgrade a V2 file system to V3 in place. 1600After issuing the upgrade be sure to run a 1601.Nm 1602.Cm cleanup 1603to perform post-upgrade tasks. 1604.Pp 1605After making this upgrade running a 1606.Nm 1607.Cm cleanup 1608will move the 1609.Pa <pfs>/snapshots 1610directory for each PFS mount into 1611.Pa /var/hammer/<pfs> . 1612A 1613.Nm HAMMER 1614root mount will migrate 1615.Pa /snapshots 1616into 1617.Pa /var/hammer/root . 1618Migration occurs only once and only if you have not specified 1619a snapshots directory in the PFS configuration. 1620If you have specified a snapshots directory in the PFS configuration no 1621automatic migration will occur. 1622.Pp 1623For slaves, if you desire, you can migrate your snapshots 1624config to the new location manually and then clear the 1625snapshot directory configuration in the slave PFS. 1626The new snapshots hierarchy is designed to work with 1627both master and slave PFSs equally well. 1628.Pp 1629In addition, the old config file will be moved to file system meta-data, 1630editable via the new 1631.Nm 1632.Cm viconfig 1633directive. 1634The old config file will be deleted. 1635Migration occurs only once. 1636.Pp 1637The V3 file system has new 1638.Cm snap* 1639directives for creating snapshots. 1640All snapshot directives, including the original, will create 1641meta-data entries for the snapshots and the pruning code will 1642automatically incorporate these entries into its list and 1643expire them the same way it expires softlinks. 1644If you by accident blow away your snapshot softlinks you can use the 1645.Cm snapls 1646directive to get a definitive list from the file system meta-data and 1647regenerate them from that list. 1648.Pp 1649.Em WARNING! 1650If you are using 1651.Nm 1652to backup file systems your scripts may be using the 1653.Cm synctid 1654directive to generate transaction ids. 1655This directive does not create a snapshot. 1656You will have to modify your scripts to use the 1657.Cm snapq 1658directive to generate the linkbuf for the softlink you create, or 1659use one of the other 1660.Cm snap* 1661directives. 1662The older 1663.Cm snapshot 1664directive will continue to work as expected and in V3 it will also 1665record the snapshot transaction id in file system meta-data. 1666You may also want to make use of the new 1667.Ar note 1668tag for the meta-data. 1669.Pp 1670.Em WARNING! 1671If you used to remove snapshot softlinks with 1672.Nm rm 1673you should probably start using the 1674.Cm snaprm 1675directive instead to also remove the related meta-data. 1676The pruning code scans the meta-data so just removing the 1677softlink is not sufficient. 1678.Sh UPGRADE INSTRUCTIONS HAMMER V3 TO V4 1679This upgrade changes undo/flush, giving faster sync. 1680It is possible to upgrade a V3 file system to V4 in place. 1681This upgrade reformats the UNDO/REDO FIFO (typically 1GB), 1682so upgrade might take a minute or two depending. 1683.Pp 1684Version 4 allows the UNDO/REDO FIFO to be flushed without also having 1685to flush the volume header, removing 2 of the 4 disk syncs typically 1686required for an 1687.Fn fsync 1688and removing 1 of the 2 disk syncs typically 1689required for a flush sequence. 1690Version 4 also implements the REDO log (see 1691.Sx FSYNC FLUSH MODES 1692below) which is capable 1693of fsync()ing with either one disk flush or zero disk flushes. 1694.Sh UPGRADE INSTRUCTIONS HAMMER V4 TO V5 1695This upgrade brings in deduplication support. 1696It is possible to upgrade a V4 file system to V5 in place. 1697Technically it makes the layer2 1698.Va bytes_free 1699field a signed value instead of unsigned, allowing it to go negative. 1700A version 5 filesystem is required for dedup operation. 1701.Sh UPGRADE INSTRUCTIONS HAMMER V5 TO V6 1702It is possible to upgrade a V5 file system to V6 in place. 1703.Sh FSYNC FLUSH MODES 1704.Nm HAMMER 1705implements five different fsync flush modes via the 1706.Va vfs.hammer.fsync_mode 1707sysctl, for 1708.Nm HAMMER 1709version 4+ file systems. 1710.Pp 1711As of 1712.Dx 2.6 1713fsync mode 3 is set by default. 1714REDO operation and recovery is enabled by default. 1715.Bl -tag -width indent 1716.It mode 0 1717Full synchronous fsync semantics without REDO. 1718.Pp 1719.Nm HAMMER 1720will not generate REDOs. 1721A 1722.Fn fsync 1723will completely sync 1724the data and meta-data and double-flush the FIFO, including 1725issuing two disk synchronization commands. 1726The data is guaranteed 1727to be on the media as of when 1728.Fn fsync 1729returns. 1730Needless to say, this is slow. 1731.It mode 1 1732Relaxed asynchronous fsync semantics without REDO. 1733.Pp 1734This mode works the same as mode 0 except the last disk synchronization 1735command is not issued. 1736It is faster than mode 0 but not even remotely 1737close to the speed you get with mode 2 or mode 3. 1738.Pp 1739Note that there is no chance of meta-data corruption when using this 1740mode, it simply means that the data you wrote and then 1741.Fn fsync Ns 'd 1742might not have made it to the media if the storage system crashes at a bad 1743time. 1744.It mode 2 1745Full synchronous fsync semantics using REDO. 1746NOTE: If not running a 1747.Nm HAMMER 1748version 4 filesystem or later mode 0 is silently used. 1749.Pp 1750.Nm HAMMER 1751will generate REDOs in the UNDO/REDO FIFO based on a heuristic. 1752If this is sufficient to satisfy the 1753.Fn fsync 1754operation the blocks will be written out and 1755.Nm HAMMER 1756will wait for the I/Os to complete, 1757and then followup with a disk sync command to guarantee the data 1758is on the media before returning. 1759This is slower than mode 3 and can result in significant disk or 1760SSDs overheads, though not as bad as mode 0 or mode 1. 1761.It mode 3 1762Relaxed asynchronous fsync semantics using REDO. 1763NOTE: If not running a 1764.Nm HAMMER 1765version 4 filesystem or later mode 1 is silently used. 1766.Pp 1767.Nm HAMMER 1768will generate REDOs in the UNDO/REDO FIFO based on a heuristic. 1769If this is sufficient to satisfy the 1770.Fn fsync 1771operation the blocks 1772will be written out and 1773.Nm HAMMER 1774will wait for the I/Os to complete, 1775but will 1776.Em NOT 1777issue a disk synchronization command. 1778.Pp 1779Note that there is no chance of meta-data corruption when using this 1780mode, it simply means that the data you wrote and then 1781.Fn fsync Ns 'd 1782might 1783not have made it to the media if the storage system crashes at a bad 1784time. 1785.Pp 1786This mode is the fastest production fsyncing mode available. 1787This mode is equivalent to how the UFS fsync in the 1788.Bx Ns s 1789operates. 1790.It mode 4 1791fsync is ignored. 1792.Pp 1793Calls to 1794.Fn fsync 1795will be ignored. 1796This mode is primarily designed 1797for testing and should not be used on a production system. 1798.El 1799.Sh RESTORING FROM A SNAPSHOT BACKUP 1800You restore a snapshot by copying it over to live, but there is a caveat. 1801The mtime and atime fields for files accessed via a snapshot is locked 1802to the ctime in order to keep the snapshot consistent, because neither 1803mtime nor atime changes roll any history. 1804.Pp 1805In order to avoid unnecessary copying it is recommended that you use 1806.Nm cpdup 1807.Fl VV 1808.Fl v 1809when doing the copyback. 1810Also make sure you traverse the snapshot softlink by appending a ".", 1811as in "<snapshotpath>/.", and you match up the directory properly. 1812.Sh RESTORING A PFS FROM A MIRROR 1813A PFS can be restored from a mirror with 1814.Cm mirror-copy . 1815.Cm config 1816data must be copied separately. 1817At last the PFS can be upgraded to master using 1818.Cm pfs-upgrade . 1819.Pp 1820It is not possible to restore the root PFS (PFS# 0) by using mirroring, 1821as the root PFS is always a master PFS. 1822A normal copy (e.g.\& using 1823.Xr cpdup 1 ) 1824must be done, ignoring history. 1825If history is important, old root PFS can me restored to a new PFS, and 1826important directories/files can be 1827.Nm null 1828mounted to the new PFS. 1829.Sh ENVIRONMENT 1830The following environment variables affect the execution of 1831.Nm : 1832.Bl -tag -width ".Ev EDITOR" 1833.It Ev EDITOR 1834The editor program specified in the variable 1835.Ev EDITOR 1836will be invoked instead of the default editor, which is 1837.Xr vi 1 . 1838.It Ev HAMMER_RSH 1839The command specified in the variable 1840.Ev HAMMER_RSH 1841will be used to initiate remote operations for the mirror-copy and 1842mirror-stream commands instead of the default command, which is 1843.Xr ssh 1 . 1844The program will be invoked via 1845.Xr execvp 3 1846using a typical 1847.Xr rsh 1 1848style 1849.Cm -l user host <remote-command> 1850command line. 1851.It Ev VISUAL 1852Same effect as 1853.Ev EDITOR 1854variable. 1855.El 1856.Sh FILES 1857.Bl -tag -width ".It Pa <fs>/var/slaves/<name>" -compact 1858.It Pa <pfs>/snapshots 1859default per PFS snapshots directory 1860.Nm ( HAMMER 1861VERSION 2-) 1862.It Pa /var/hammer/<pfs> 1863default per PFS snapshots directory (not root) 1864.Nm ( HAMMER 1865VERSION 3+) 1866.It Pa /var/hammer/root 1867default snapshots directory for root directory 1868.Nm ( HAMMER 1869VERSION 3+) 1870.It Pa <snapshots>/config 1871per PFS 1872.Nm 1873.Cm cleanup 1874configuration file 1875.Nm ( HAMMER 1876VERSION 2-) 1877.It Pa <fs>/var/slaves/<name> 1878recommended slave PFS snapshots directory 1879.Nm ( HAMMER 1880VERSION 2-) 1881.It Pa <fs>/pfs 1882recommended PFS directory 1883.El 1884.Sh EXIT STATUS 1885.Ex -std 1886.Sh SEE ALSO 1887.Xr ssh 1 , 1888.Xr undo 1 , 1889.Xr HAMMER 5 , 1890.Xr periodic.conf 5 , 1891.Xr loader 8 , 1892.Xr mount_hammer 8 , 1893.Xr mount_null 8 , 1894.Xr newfs_hammer 8 , 1895.Xr swapcache 8 , 1896.Xr sysctl 8 1897.Sh HISTORY 1898The 1899.Nm 1900utility first appeared in 1901.Dx 1.11 . 1902.Sh AUTHORS 1903.An Matthew Dillon Aq Mt dillon@backplane.com 1904