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 freemap, B-Tree, UNDO FIFO, then collect allocation information, 368and construct 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.\" ==== volume-blkdevs ==== 768.It Cm volume-blkdevs Ar filesystem 769List the volumes that make up 770.Ar filesystem 771in 772.Ar blkdevs 773format. 774.\" ==== snapshot ==== 775.It Cm snapshot Oo Ar filesystem Oc Ar snapshot-dir 776.It Cm snapshot Ar filesystem Ar snapshot-dir Op Ar note 777Take a snapshot of the file system either explicitly given by 778.Ar filesystem 779or implicitly derived from the 780.Ar snapshot-dir 781argument and creates a symlink in the directory provided by 782.Ar snapshot-dir 783pointing to the snapshot. 784If 785.Ar snapshot-dir 786is not a directory, it is assumed to be a format string passed to 787.Xr strftime 3 788with the current time as parameter. 789If 790.Ar snapshot-dir 791refers to an existing directory, a default format string of 792.Ql snap-%Y%m%d-%H%M 793is assumed and used as name for the newly created symlink. 794.Pp 795Snapshot is a per PFS operation, so each PFS in a 796.Nm HAMMER 797file system have to be snapshot separately. 798.Pp 799Example, assuming that 800.Pa /mysnapshots 801is on file system 802.Pa / 803and that 804.Pa /obj 805and 806.Pa /usr 807are file systems on their own, the following invocations: 808.Bd -literal -offset indent 809hammer snapshot /mysnapshots 810 811hammer snapshot /mysnapshots/%Y-%m-%d 812 813hammer snapshot /obj /mysnapshots/obj-%Y-%m-%d 814 815hammer snapshot /usr /my/snaps/usr "note" 816.Ed 817.Pp 818Would create symlinks similar to: 819.Bd -literal -offset indent 820/mysnapshots/snap-20080627-1210 -> /@@0x10d2cd05b7270d16 821 822/mysnapshots/2008-06-27 -> /@@0x10d2cd05b7270d16 823 824/mysnapshots/obj-2008-06-27 -> /obj@@0x10d2cd05b7270d16 825 826/my/snaps/usr/snap-20080627-1210 -> /usr@@0x10d2cd05b7270d16 827.Ed 828.Pp 829When run on a 830.Nm HAMMER 831version 3+ file system the snapshot is also recorded in file system meta-data 832along with the optional 833.Ar note . 834See the 835.Cm snapls 836directive. 837.\" ==== snap* ==== 838.It Cm snap Ar path Op Ar note 839.Nm ( HAMMER 840VERSION 3+) 841Create a snapshot for the PFS containing 842.Ar path 843and create a snapshot softlink. 844If the path specified is a 845directory a standard snapshot softlink will be created in the directory. 846The snapshot softlink points to the base of the mounted PFS. 847.It Cm snaplo Ar path Op Ar note 848.Nm ( HAMMER 849VERSION 3+) 850Create a snapshot for the PFS containing 851.Ar path 852and create a snapshot softlink. 853If the path specified is a 854directory a standard snapshot softlink will be created in the directory. 855The snapshot softlink points into the directory it is contained in. 856.It Cm snapq Ar dir Op Ar note 857.Nm ( HAMMER 858VERSION 3+) 859Create a snapshot for the PFS containing the specified directory but do 860not create a softlink. 861Instead output a path which can be used to access 862the directory via the snapshot. 863.Pp 864An absolute or relative path may be specified. 865The path will be used as-is as a prefix in the path output to stdout. 866As with the other 867snap and snapshot directives the snapshot transaction id will be registered 868in the file system meta-data. 869.It Cm snaprm Ar path Ar ... 870.It Cm snaprm Ar transaction_id Ar ... 871.It Cm snaprm Ar filesystem Ar transaction_id Ar ... 872.Nm ( HAMMER 873VERSION 3+) 874Remove a snapshot given its softlink or transaction id. 875If specifying a transaction id 876the snapshot is removed from file system meta-data but you are responsible 877for removing any related softlinks. 878.Pp 879If a softlink path is specified the filesystem and transaction id 880is derived from the contents of the softlink. 881If just a transaction id is specified it is assumed to be a snapshot in the 882.Nm HAMMER 883filesystem you are currently chdir'd into. 884You can also specify the filesystem and transaction id explicitly. 885.It Cm snapls Op Ar path ... 886.Nm ( HAMMER 887VERSION 3+) 888Dump the snapshot meta-data for PFSs containing each 889.Ar path 890listing all available snapshots and their notes. 891If no arguments are specified snapshots for the PFS containing the 892current directory are listed. 893This is the definitive list of snapshots for the file system. 894.\" ==== prune ==== 895.It Cm prune Ar softlink-dir 896Prune the file system based on previously created snapshot softlinks. 897Pruning is the act of deleting file system history. 898The 899.Cm prune 900command will delete file system history such that 901the file system state is retained for the given snapshots, 902and all history after the latest snapshot. 903By setting the per PFS parameter 904.Cm prune-min , 905history is guaranteed to be saved at least this time interval. 906All other history is deleted. 907.Pp 908The target directory is expected to contain softlinks pointing to 909snapshots of the file systems you wish to retain. 910The directory is scanned non-recursively and the mount points and 911transaction ids stored in the softlinks are extracted and sorted. 912The file system is then explicitly pruned according to what is found. 913Cleaning out portions of the file system is as simple as removing a 914snapshot softlink and then running the 915.Cm prune 916command. 917.Pp 918As a safety measure pruning only occurs if one or more softlinks are found 919containing the 920.Ql @@ 921snapshot id extension. 922Currently the scanned softlink directory must contain softlinks pointing 923to a single 924.Nm HAMMER 925mount. 926The softlinks may specify absolute or relative paths. 927Softlinks must use 20-character 928.Ql @@0x%016llx 929transaction ids, as might be returned from 930.Nm Cm synctid Ar filesystem . 931.Pp 932Pruning is a per PFS operation, so each PFS in a 933.Nm HAMMER 934file system have to be pruned separately. 935.Pp 936Note that pruning a file system may not immediately free-up space, 937though typically some space will be freed if a large number of records are 938pruned out. 939The file system must be reblocked to completely recover all available space. 940.Pp 941Example, lets say your that you didn't set 942.Cm prune-min , 943and snapshot directory contains the following links: 944.Bd -literal -offset indent 945lrwxr-xr-x 1 root wheel 29 May 31 17:57 snap1 -> 946/usr/obj/@@0x10d2cd05b7270d16 947 948lrwxr-xr-x 1 root wheel 29 May 31 17:58 snap2 -> 949/usr/obj/@@0x10d2cd13f3fde98f 950 951lrwxr-xr-x 1 root wheel 29 May 31 17:59 snap3 -> 952/usr/obj/@@0x10d2cd222adee364 953.Ed 954.Pp 955If you were to run the 956.Cm prune 957command on this directory, then the 958.Nm HAMMER 959.Pa /usr/obj 960mount will be pruned to retain the above three snapshots. 961In addition, history for modifications made to the file system older than 962the oldest snapshot will be destroyed and history for potentially fine-grained 963modifications made to the file system more recently than the most recent 964snapshot will be retained. 965.Pp 966If you then delete the 967.Pa snap2 968softlink and rerun the 969.Cm prune 970command, 971history for modifications pertaining to that snapshot would be destroyed. 972.Pp 973In 974.Nm HAMMER 975file system versions 3+ this command also scans the snapshots stored 976in the file system meta-data and includes them in the prune. 977.\" ==== prune-everything ==== 978.It Cm prune-everything Ar filesystem 979Remove all historical records from 980.Ar filesystem . 981Use this directive with caution on PFSs where you intend to use history. 982.Pp 983This command does not remove snapshot softlinks but will delete all 984snapshots recorded in file system meta-data (for file system version 3+). 985The user is responsible for deleting any softlinks. 986.Pp 987Pruning is a per PFS operation, so each PFS in a 988.Nm HAMMER 989file system have to be pruned separately. 990.\" ==== rebalance ==== 991.It Cm rebalance Ar filesystem Op Ar saturation_percentage 992Rebalance the B-Tree, nodes with small number of 993elements will be combined and element counts will be smoothed out 994between nodes. 995.Pp 996The saturation percentage is between 50% and 100%. 997The default is 85% (the 998.Sq % 999suffix is not needed). 1000.Pp 1001Rebalancing is a per PFS operation, so each PFS in a 1002.Nm HAMMER 1003file system have to be rebalanced separately. 1004.\" ==== dedup ==== 1005.It Cm dedup Ar filesystem 1006.Nm ( HAMMER 1007VERSION 5+) 1008Perform offline (post-process) deduplication. 1009Deduplication occurs at 1010the block level, currently only data blocks of the same size can be 1011deduped, metadata blocks can not. 1012The hash function used for comparing 1013data blocks is CRC-32 (CRCs are computed anyways as part of 1014.Nm HAMMER 1015data integrity features, so there's no additional overhead). 1016Since CRC is a weak hash function a byte-by-byte comparison is done 1017before actual deduping. 1018In case of a CRC collision (two data blocks have the same CRC 1019but different contents) the checksum is upgraded to SHA-256. 1020.Pp 1021Currently 1022.Nm HAMMER 1023reblocker may partially blow up (re-expand) dedup (reblocker's normal 1024operation is to reallocate every record, so it's possible for deduped 1025blocks to be re-expanded back). 1026.Pp 1027Deduplication is a per PFS operation, so each PFS in a 1028.Nm HAMMER 1029file system have to be deduped separately. 1030This also 1031means that if you have duplicated data in two different PFSs that data 1032won't be deduped, however the addition of such feature is planned. 1033.Pp 1034The 1035.Fl m Ar memlimit 1036option should be used to limit memory use during the dedup run if the 1037default 1G limit is too much for the machine. 1038.\" ==== dedup-simulate ==== 1039.It Cm dedup-simulate Ar filesystem 1040Shows potential space savings (simulated dedup ratio) one can get after 1041running 1042.Cm dedup 1043command. 1044If the estimated dedup ratio is greater than 1.00 you will see 1045dedup space savings. 1046Remember that this is an estimated number, in 1047practice real dedup ratio will be slightly smaller because of 1048.Nm HAMMER 1049big-block underflows, B-Tree locking issues and other factors. 1050.Pp 1051Note that deduplication currently works only on bulk data so if you 1052try to run 1053.Cm dedup-simulate 1054or 1055.Cm dedup 1056commands on a PFS that contains metadata only (directory entries, 1057softlinks) you will get a 0.00 dedup ratio. 1058.Pp 1059The 1060.Fl m Ar memlimit 1061option should be used to limit memory use during the dedup run if the 1062default 1G limit is too much for the machine. 1063.\" ==== reblock* ==== 1064.It Cm reblock Ar filesystem Op Ar fill_percentage 1065.It Cm reblock-btree Ar filesystem Op Ar fill_percentage 1066.It Cm reblock-inodes Ar filesystem Op Ar fill_percentage 1067.It Cm reblock-dirs Ar filesystem Op Ar fill_percentage 1068.It Cm reblock-data Ar filesystem Op Ar fill_percentage 1069Attempt to defragment and free space for reuse by reblocking a live 1070.Nm HAMMER 1071file system. 1072Big-blocks cannot be reused by 1073.Nm HAMMER 1074until they are completely free. 1075This command also has the effect of reordering all elements, effectively 1076defragmenting the file system. 1077.Pp 1078The default fill percentage is 100% and will cause the file system to be 1079completely defragmented. 1080All specified element types will be reallocated and rewritten. 1081If you wish to quickly free up space instead try specifying 1082a smaller fill percentage, such as 90% or 80% (the 1083.Sq % 1084suffix is not needed). 1085.Pp 1086Since this command may rewrite the entire contents of the disk it is 1087best to do it incrementally from a 1088.Xr cron 8 1089job along with the 1090.Fl c Ar cyclefile 1091and 1092.Fl t Ar seconds 1093options to limit the run time. 1094The file system would thus be defragmented over long period of time. 1095.Pp 1096It is recommended that separate invocations be used for each data type. 1097B-Tree nodes, inodes, and directories are typically the most important 1098elements needing defragmentation. 1099Data can be defragmented over a longer period of time. 1100.Pp 1101Reblocking is a per PFS operation, so each PFS in a 1102.Nm HAMMER 1103file system have to be reblocked separately. 1104.\" ==== pfs-status ==== 1105.It Cm pfs-status Ar dirpath ... 1106Retrieve the mirroring configuration parameters for the specified 1107.Nm HAMMER 1108file systems or pseudo-filesystems (PFS's). 1109.\" ==== pfs-master ==== 1110.It Cm pfs-master Ar dirpath Op Ar options 1111Create a pseudo-filesystem (PFS) inside a 1112.Nm HAMMER 1113file system. 1114Up to 65536 PFSs can be created. 1115Each PFS uses an independent inode numbering space making it suitable 1116for replication. 1117.Pp 1118The 1119.Cm pfs-master 1120directive creates a PFS that you can read, write, and use as a mirroring 1121source. 1122.Pp 1123A PFS can only be truly destroyed with the 1124.Cm pfs-destroy 1125directive. 1126Removing the softlink will not destroy the underlying PFS. 1127.Pp 1128A PFS can only be created in the root PFS (PFS# 0), 1129not in a PFS created by 1130.Cm pfs-master 1131or 1132.Cm pfs-slave 1133(PFS# >0). 1134.Pp 1135It is recommended that 1136.Ar dirpath 1137is of the form 1138.Pa <fs>/pfs/<name> 1139(i.e.\& located in 1140.Pa pfs 1141directory at root of 1142.Nm HAMMER 1143file system). 1144.Pp 1145It is recommended to use a 1146.Nm null 1147mount to access a PFS, except for root PFS, for more information see 1148.Xr HAMMER 5 . 1149.\" ==== pfs-slave ==== 1150.It Cm pfs-slave Ar dirpath Op Ar options 1151Create a pseudo-filesystem (PFS) inside a 1152.Nm HAMMER 1153file system. 1154Up to 65536 PFSs can be created. 1155Each PFS uses an independent inode numbering space making it suitable 1156for replication. 1157.Pp 1158The 1159.Cm pfs-slave 1160directive creates a PFS that you can use as a mirroring source or target. 1161You will not be able to access a slave PFS until you have completed the 1162first mirroring operation with it as the target (its root directory will 1163not exist until then). 1164.Pp 1165Access to the pfs-slave via the special softlink, as described in the 1166.Sx PSEUDO-FILESYSTEM (PFS) NOTES 1167below, allows 1168.Nm HAMMER 1169to 1170dynamically modify the snapshot transaction id by returning a dynamic result 1171from 1172.Xr readlink 2 1173calls. 1174.Pp 1175A PFS can only be truly destroyed with the 1176.Cm pfs-destroy 1177directive. 1178Removing the softlink will not destroy the underlying PFS. 1179.Pp 1180A PFS can only be created in the root PFS (PFS# 0), 1181not in a PFS created by 1182.Cm pfs-master 1183or 1184.Cm pfs-slave 1185(PFS# >0). 1186.Pp 1187It is recommended that 1188.Ar dirpath 1189is of the form 1190.Pa <fs>/pfs/<name> 1191(i.e.\& located in 1192.Pa pfs 1193directory at root of 1194.Nm HAMMER 1195file system). 1196.Pp 1197It is recommended to use a 1198.Nm null 1199mount to access a PFS, except for root PFS, for more information see 1200.Xr HAMMER 5 . 1201.\" ==== pfs-update ==== 1202.It Cm pfs-update Ar dirpath Op Ar options 1203Update the configuration parameters for an existing 1204.Nm HAMMER 1205file system or pseudo-filesystem. 1206Options that may be specified: 1207.Bl -tag -width indent 1208.It Cm sync-beg-tid= Ns Ar 0x16llx 1209This is the automatic snapshot access starting transaction id for 1210mirroring slaves. 1211This parameter is normally updated automatically by the 1212.Cm mirror-write 1213directive. 1214.Pp 1215It is important to note that accessing a mirroring slave 1216with a transaction id greater than the last fully synchronized transaction 1217id can result in an unreliable snapshot since you will be accessing 1218data that is still undergoing synchronization. 1219.Pp 1220Manually modifying this field is dangerous and can result in a broken mirror. 1221.It Cm sync-end-tid= Ns Ar 0x16llx 1222This is the current synchronization point for mirroring slaves. 1223This parameter is normally updated automatically by the 1224.Cm mirror-write 1225directive. 1226.Pp 1227Manually modifying this field is dangerous and can result in a broken mirror. 1228.It Cm shared-uuid= Ns Ar uuid 1229Set the shared UUID for this file system. 1230All mirrors must have the same shared UUID. 1231For safety purposes the 1232.Cm mirror-write 1233directives will refuse to operate on a target with a different shared UUID. 1234.Pp 1235Changing the shared UUID on an existing, non-empty mirroring target, 1236including an empty but not completely pruned target, 1237can lead to corruption of the mirroring target. 1238.It Cm unique-uuid= Ns Ar uuid 1239Set the unique UUID for this file system. 1240This UUID should not be used anywhere else, 1241even on exact copies of the file system. 1242.It Cm label= Ns Ar string 1243Set a descriptive label for this file system. 1244.It Cm snapshots= Ns Ar string 1245Specify the snapshots directory which 1246.Nm 1247.Cm cleanup 1248will use to manage this PFS. 1249.Bl -tag -width indent 1250.It Nm HAMMER No version 2- 1251The snapshots directory does not need to be configured for 1252PFS masters and will default to 1253.Pa <pfs>/snapshots . 1254.Pp 1255PFS slaves are mirroring slaves so you cannot configure a snapshots 1256directory on the slave itself to be managed by the slave's machine. 1257In fact, the slave will likely have a 1258.Pa snapshots 1259sub-directory mirrored 1260from the master, but that directory contains the configuration the master 1261is using for its copy of the file system, not the configuration that we 1262want to use for our slave. 1263.Pp 1264It is recommended that 1265.Pa <fs>/var/slaves/<name> 1266be configured for a PFS slave, where 1267.Pa <fs> 1268is the base 1269.Nm HAMMER 1270file system, and 1271.Pa <name> 1272is an appropriate label. 1273.It Nm HAMMER No version 3+ 1274The snapshots directory does not need to be configured for PFS masters or 1275slaves. 1276The snapshots directory defaults to 1277.Pa /var/hammer/<pfs> 1278.Pa ( /var/hammer/root 1279for root mount). 1280.El 1281.Pp 1282You can control snapshot retention on your slave independent of the master. 1283.It Cm snapshots-clear 1284Zero out the 1285.Cm snapshots 1286directory path for this PFS. 1287.It Cm prune-min= Ns Ar N Ns Cm d 1288.It Cm prune-min= Ns Oo Ar N Ns Cm d/ Oc Ns \ 1289Ar hh Ns Op Cm \&: Ns Ar mm Ns Op Cm \&: Ns Ar ss 1290Set the minimum fine-grained data retention period. 1291.Nm HAMMER 1292always retains fine-grained history up to the most recent snapshot. 1293You can extend the retention period further by specifying a non-zero 1294pruning minimum. 1295Any snapshot softlinks within the retention period are ignored 1296for the purposes of pruning (i.e.\& the fine grained history is retained). 1297Number of days, hours, minutes and seconds are given as 1298.Ar N , hh , mm 1299and 1300.Ar ss . 1301.Pp 1302Because the transaction id in the snapshot softlink cannot be used 1303to calculate a timestamp, 1304.Nm HAMMER 1305uses the earlier of the 1306.Fa st_ctime 1307or 1308.Fa st_mtime 1309field of the softlink to 1310determine which snapshots fall within the retention period. 1311Users must be sure to retain one of these two fields when manipulating 1312the softlink. 1313.El 1314.\" ==== pfs-upgrade ==== 1315.It Cm pfs-upgrade Ar dirpath 1316Upgrade a PFS from slave to master operation. 1317The PFS will be rolled back to the current end synchronization transaction id 1318(removing any partial synchronizations), and will then become writable. 1319.Pp 1320.Em WARNING! 1321.Nm HAMMER 1322currently supports only single masters and using 1323this command can easily result in file system corruption 1324if you don't know what you are doing. 1325.Pp 1326This directive will refuse to run if any programs have open descriptors 1327in the PFS, including programs chdir'd into the PFS. 1328.\" ==== pfs-downgrade ==== 1329.It Cm pfs-downgrade Ar dirpath 1330Downgrade a master PFS from master to slave operation. 1331The PFS becomes read-only and access will be locked to its 1332.Cm sync-end-tid . 1333.Pp 1334This directive will refuse to run if any programs have open descriptors 1335in the PFS, including programs chdir'd into the PFS. 1336.\" ==== pfs-destroy ==== 1337.It Cm pfs-destroy Ar dirpath 1338This permanently destroys a PFS. 1339.Pp 1340This directive will refuse to run if any programs have open descriptors 1341in the PFS, including programs chdir'd into the PFS. 1342As safety measure the 1343.Fl y 1344flag have no effect on this directive. 1345.\" ==== mirror-read ==== 1346.It Cm mirror-read Ar filesystem Op Ar begin-tid 1347Generate a mirroring stream to stdout. 1348The stream ends when the transaction id space has been exhausted. 1349.Ar filesystem 1350may be a master or slave PFS. 1351.\" ==== mirror-read-stream ==== 1352.It Cm mirror-read-stream Ar filesystem Op Ar begin-tid 1353Generate a mirroring stream to stdout. 1354Upon completion the stream is paused until new data is synced to the 1355.Ar filesystem , 1356then resumed. 1357Operation continues until the pipe is broken. 1358See the 1359.Cm mirror-stream 1360command for more details. 1361.\" ==== mirror-write ==== 1362.It Cm mirror-write Ar filesystem 1363Take a mirroring stream on stdin. 1364.Ar filesystem 1365must be a slave PFS. 1366.Pp 1367This command will fail if the 1368.Cm shared-uuid 1369configuration field for the two file systems do not match. 1370See the 1371.Cm mirror-copy 1372command for more details. 1373.Pp 1374If the target PFS does not exist this command will ask you whether 1375you want to create a compatible PFS slave for the target or not. 1376.\" ==== mirror-dump ==== 1377.It Ar mirror-dump Ar [header] 1378A 1379.Cm mirror-read 1380can be piped into a 1381.Cm mirror-dump 1382to dump an ASCII representation of the mirroring stream. 1383If the keyword 1384.Ar header 1385is specified, only the header information is shown. 1386.\" ==== mirror-copy ==== 1387.\".It Cm mirror-copy Ar [[user@]host:]filesystem [[user@]host:]filesystem 1388.It Cm mirror-copy \ 1389Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \ 1390Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem 1391This is a shortcut which pipes a 1392.Cm mirror-read 1393command to a 1394.Cm mirror-write 1395command. 1396If a remote host specification is made the program forks a 1397.Xr ssh 1 1398(or other program as specified by the 1399.Ev HAMMER_RSH 1400environment variable) and execs the 1401.Cm mirror-read 1402and/or 1403.Cm mirror-write 1404on the appropriate host. 1405The source may be a master or slave PFS, and the target must be a slave PFS. 1406.Pp 1407This command also establishes full duplex communication and turns on 1408the 2-way protocol feature 1409.Fl ( 2 ) 1410which automatically negotiates transaction id 1411ranges without having to use a cyclefile. 1412If the operation completes successfully the target PFS's 1413.Cm sync-end-tid 1414will be updated. 1415Note that you must re-chdir into the target PFS to see the updated information. 1416If you do not you will still be in the previous snapshot. 1417.Pp 1418If the target PFS does not exist this command will ask you whether 1419you want to create a compatible PFS slave for the target or not. 1420.\" ==== mirror-stream ==== 1421.\".It Cm mirror-stream Ar [[user@]host:]filesystem [[user@]host:]filesystem 1422.It Cm mirror-stream \ 1423Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \ 1424Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem 1425This is a shortcut which pipes a 1426.Cm mirror-read-stream 1427command to a 1428.Cm mirror-write 1429command. 1430This command works similarly to 1431.Cm mirror-copy 1432but does not exit after the initial mirroring completes. 1433The mirroring operation will resume as changes continue to be made to the 1434source. 1435The command is commonly used with 1436.Fl i Ar delay 1437and 1438.Fl b Ar bandwidth 1439options to keep the mirroring target in sync with the source on a continuing 1440basis. 1441.Pp 1442If the pipe is broken the command will automatically retry after sleeping 1443for a short while. 1444The time slept will be 15 seconds plus the time given in the 1445.Fl i 1446option. 1447.Pp 1448This command also detects the initial-mirroring case and spends some 1449time scanning the B-Tree to find good break points, allowing the initial 1450bulk mirroring operation to be broken down into 4GB pieces. 1451This means that the user can kill and restart the operation and it will 1452not have to start from scratch once it has gotten past the first chunk. 1453The 1454.Fl S 1455option may be used to change the size of pieces and the 1456.Fl B 1457option may be used to disable this feature and perform an initial bulk 1458transfer instead. 1459.\" ==== version ==== 1460.It Cm version Ar filesystem 1461This command returns the 1462.Nm HAMMER 1463file system version for the specified 1464.Ar filesystem 1465as well as the range of versions supported in the kernel. 1466The 1467.Fl q 1468option may be used to remove the summary at the end. 1469.\" ==== version-upgrade ==== 1470.It Cm version-upgrade Ar filesystem Ar version Op Cm force 1471Upgrade the 1472.Nm HAMMER 1473.Ar filesystem 1474to the specified 1475.Ar version . 1476Once upgraded a file system may not be downgraded. 1477If you wish to upgrade a file system to a version greater or equal to the 1478work-in-progress (WIP) version number you must specify the 1479.Cm force 1480directive. 1481Use of WIP versions should be relegated to testing and may require wiping 1482the file system as development progresses, even though the WIP version might 1483not change. 1484.Pp 1485.Em NOTE! 1486This command operates on the entire 1487.Nm HAMMER 1488file system and is not a per PFS operation. 1489All PFS's will be affected. 1490.Bl -tag -width indent 1491.It 1 1492.Dx 2.0 1493default version, first 1494.Nm HAMMER 1495release. 1496.It 2 1497.Dx 2.3 . 1498New directory entry layout. 1499This version is using a new directory hash key. 1500.It 3 1501.Dx 2.5 . 1502New snapshot management, using file system meta-data for saving 1503configuration file and snapshots (transaction ids etc.). 1504Also default snapshots directory has changed. 1505.It 4 1506.Dx 2.6 1507default version. 1508New undo/redo/flush, giving 1509.Nm HAMMER 1510a much faster sync and fsync. 1511.It 5 1512.Dx 2.9 . 1513Deduplication support. 1514.It 6 1515.Dx 2.9 . 1516Directory hash ALG1. 1517Tends to maintain inode number / directory name entry ordering better 1518for files after minor renaming. 1519.El 1520.El 1521.Sh PSEUDO-FILESYSTEM (PFS) NOTES 1522The root of a PFS is not hooked into the primary 1523.Nm HAMMER 1524file system as a directory. 1525Instead, 1526.Nm HAMMER 1527creates a special softlink called 1528.Ql @@PFS%05d 1529(exactly 10 characters long) in the primary 1530.Nm HAMMER 1531file system. 1532.Nm HAMMER 1533then modifies the contents of the softlink as read by 1534.Xr readlink 2 , 1535and thus what you see with an 1536.Nm ls 1537command or if you were to 1538.Nm cd 1539into the link. 1540If the PFS is a master the link reflects the current state of the PFS. 1541If the PFS is a slave the link reflects the last completed snapshot, and the 1542contents of the link will change when the next snapshot is completed, and 1543so forth. 1544.Pp 1545The 1546.Nm 1547utility employs numerous safeties to reduce user foot-shooting. 1548The 1549.Cm mirror-copy 1550directive requires that the target be configured as a slave and that the 1551.Cm shared-uuid 1552field of the mirroring source and target match. 1553.Sh DOUBLE_BUFFER MODE 1554There is a limit to the number of vnodes the kernel can cache, and because 1555file buffers are associated with a vnode the related data cache can get 1556blown away when operating on large numbers of files even if the system has 1557sufficient memory to hold the file data. 1558.Pp 1559If you turn on 1560.Nm HAMMER Ns 's 1561double buffer mode by setting the 1562.Xr sysctl 8 1563node 1564.Va vfs.hammer.double_buffer 1565to 1 1566.Nm HAMMER 1567will cache file data via the block device and copy it into the per-file 1568buffers as needed. The data will be double-cached at least until the 1569buffer cache throws away the file buffer. 1570This mode is typically used in conjunction with 1571.Xr swapcache 8 1572when 1573.Va vm.swapcache.data_enable 1574is turned on in order to prevent unnecessary re-caching of file data 1575due to vnode recycling. 1576The swapcache will save the cached VM pages related to 1577.Nm HAMMER Ns 's 1578block 1579device (which doesn't recycle unless you umount the filesystem) instead 1580of the cached VM pages backing the file vnodes. 1581.\".Pp 1582.\"Double buffering should also be turned on if live dedup is enabled via 1583.\"Va vfs.hammer.live_dedup . 1584.\"This is because the live dedup must validate the contents of a potential 1585.\"duplicate file block and it must run through the block device to do that 1586.\"and not the file vnode. 1587.\"If double buffering is not enabled then live dedup will create extra disk 1588.\"reads to validate potential data duplicates. 1589.Sh UPGRADE INSTRUCTIONS HAMMER V1 TO V2 1590This upgrade changes the way directory entries are stored. 1591It is possible to upgrade a V1 file system to V2 in place, but 1592directories created prior to the upgrade will continue to use 1593the old layout. 1594.Pp 1595Note that the slave mirroring code in the target kernel had bugs in 1596V1 which can create an incompatible root directory on the slave. 1597Do not mix a 1598.Nm HAMMER 1599master created after the upgrade with a 1600.Nm HAMMER 1601slave created prior to the upgrade. 1602.Pp 1603Any directories created after upgrading will use a new layout. 1604.Sh UPGRADE INSTRUCTIONS HAMMER V2 TO V3 1605This upgrade adds meta-data elements to the B-Tree. 1606It is possible to upgrade a V2 file system to V3 in place. 1607After issuing the upgrade be sure to run a 1608.Nm 1609.Cm cleanup 1610to perform post-upgrade tasks. 1611.Pp 1612After making this upgrade running a 1613.Nm 1614.Cm cleanup 1615will move the 1616.Pa <pfs>/snapshots 1617directory for each PFS mount into 1618.Pa /var/hammer/<pfs> . 1619A 1620.Nm HAMMER 1621root mount will migrate 1622.Pa /snapshots 1623into 1624.Pa /var/hammer/root . 1625Migration occurs only once and only if you have not specified 1626a snapshots directory in the PFS configuration. 1627If you have specified a snapshots directory in the PFS configuration no 1628automatic migration will occur. 1629.Pp 1630For slaves, if you desire, you can migrate your snapshots 1631config to the new location manually and then clear the 1632snapshot directory configuration in the slave PFS. 1633The new snapshots hierarchy is designed to work with 1634both master and slave PFSs equally well. 1635.Pp 1636In addition, the old config file will be moved to file system meta-data, 1637editable via the new 1638.Nm 1639.Cm viconfig 1640directive. 1641The old config file will be deleted. 1642Migration occurs only once. 1643.Pp 1644The V3 file system has new 1645.Cm snap* 1646directives for creating snapshots. 1647All snapshot directives, including the original, will create 1648meta-data entries for the snapshots and the pruning code will 1649automatically incorporate these entries into its list and 1650expire them the same way it expires softlinks. 1651If you by accident blow away your snapshot softlinks you can use the 1652.Cm snapls 1653directive to get a definitive list from the file system meta-data and 1654regenerate them from that list. 1655.Pp 1656.Em WARNING! 1657If you are using 1658.Nm 1659to backup file systems your scripts may be using the 1660.Cm synctid 1661directive to generate transaction ids. 1662This directive does not create a snapshot. 1663You will have to modify your scripts to use the 1664.Cm snapq 1665directive to generate the linkbuf for the softlink you create, or 1666use one of the other 1667.Cm snap* 1668directives. 1669The older 1670.Cm snapshot 1671directive will continue to work as expected and in V3 it will also 1672record the snapshot transaction id in file system meta-data. 1673You may also want to make use of the new 1674.Ar note 1675tag for the meta-data. 1676.Pp 1677.Em WARNING! 1678If you used to remove snapshot softlinks with 1679.Nm rm 1680you should probably start using the 1681.Cm snaprm 1682directive instead to also remove the related meta-data. 1683The pruning code scans the meta-data so just removing the 1684softlink is not sufficient. 1685.Sh UPGRADE INSTRUCTIONS HAMMER V3 TO V4 1686This upgrade changes undo/flush, giving faster sync. 1687It is possible to upgrade a V3 file system to V4 in place. 1688This upgrade reformats the UNDO/REDO FIFO (typically 1GB), 1689so upgrade might take a minute or two depending. 1690.Pp 1691Version 4 allows the UNDO/REDO FIFO to be flushed without also having 1692to flush the volume header, removing 2 of the 4 disk syncs typically 1693required for an 1694.Fn fsync 1695and removing 1 of the 2 disk syncs typically 1696required for a flush sequence. 1697Version 4 also implements the REDO log (see 1698.Sx FSYNC FLUSH MODES 1699below) which is capable 1700of fsync()ing with either one disk flush or zero disk flushes. 1701.Sh UPGRADE INSTRUCTIONS HAMMER V4 TO V5 1702This upgrade brings in deduplication support. 1703It is possible to upgrade a V4 file system to V5 in place. 1704Technically it makes the layer2 1705.Va bytes_free 1706field a signed value instead of unsigned, allowing it to go negative. 1707A version 5 filesystem is required for dedup operation. 1708.Sh UPGRADE INSTRUCTIONS HAMMER V5 TO V6 1709It is possible to upgrade a V5 file system to V6 in place. 1710.Sh FSYNC FLUSH MODES 1711.Nm HAMMER 1712implements five different fsync flush modes via the 1713.Va vfs.hammer.fsync_mode 1714sysctl, for 1715.Nm HAMMER 1716version 4+ file systems. 1717.Pp 1718As of 1719.Dx 2.6 1720fsync mode 3 is set by default. 1721REDO operation and recovery is enabled by default. 1722.Bl -tag -width indent 1723.It mode 0 1724Full synchronous fsync semantics without REDO. 1725.Pp 1726.Nm HAMMER 1727will not generate REDOs. 1728A 1729.Fn fsync 1730will completely sync 1731the data and meta-data and double-flush the FIFO, including 1732issuing two disk synchronization commands. 1733The data is guaranteed 1734to be on the media as of when 1735.Fn fsync 1736returns. 1737Needless to say, this is slow. 1738.It mode 1 1739Relaxed asynchronous fsync semantics without REDO. 1740.Pp 1741This mode works the same as mode 0 except the last disk synchronization 1742command is not issued. 1743It is faster than mode 0 but not even remotely 1744close to the speed you get with mode 2 or mode 3. 1745.Pp 1746Note that there is no chance of meta-data corruption when using this 1747mode, it simply means that the data you wrote and then 1748.Fn fsync Ns 'd 1749might not have made it to the media if the storage system crashes at a bad 1750time. 1751.It mode 2 1752Full synchronous fsync semantics using REDO. 1753NOTE: If not running a 1754.Nm HAMMER 1755version 4 filesystem or later mode 0 is silently used. 1756.Pp 1757.Nm HAMMER 1758will generate REDOs in the UNDO/REDO FIFO based on a heuristic. 1759If this is sufficient to satisfy the 1760.Fn fsync 1761operation the blocks will be written out and 1762.Nm HAMMER 1763will wait for the I/Os to complete, 1764and then followup with a disk sync command to guarantee the data 1765is on the media before returning. 1766This is slower than mode 3 and can result in significant disk or 1767SSDs overheads, though not as bad as mode 0 or mode 1. 1768.It mode 3 1769Relaxed asynchronous fsync semantics using REDO. 1770NOTE: If not running a 1771.Nm HAMMER 1772version 4 filesystem or later mode 1 is silently used. 1773.Pp 1774.Nm HAMMER 1775will generate REDOs in the UNDO/REDO FIFO based on a heuristic. 1776If this is sufficient to satisfy the 1777.Fn fsync 1778operation the blocks 1779will be written out and 1780.Nm HAMMER 1781will wait for the I/Os to complete, 1782but will 1783.Em NOT 1784issue a disk synchronization command. 1785.Pp 1786Note that there is no chance of meta-data corruption when using this 1787mode, it simply means that the data you wrote and then 1788.Fn fsync Ns 'd 1789might 1790not have made it to the media if the storage system crashes at a bad 1791time. 1792.Pp 1793This mode is the fastest production fsyncing mode available. 1794This mode is equivalent to how the UFS fsync in the 1795.Bx Ns s 1796operates. 1797.It mode 4 1798fsync is ignored. 1799.Pp 1800Calls to 1801.Fn fsync 1802will be ignored. 1803This mode is primarily designed 1804for testing and should not be used on a production system. 1805.El 1806.Sh RESTORING FROM A SNAPSHOT BACKUP 1807You restore a snapshot by copying it over to live, but there is a caveat. 1808The mtime and atime fields for files accessed via a snapshot is locked 1809to the ctime in order to keep the snapshot consistent, because neither 1810mtime nor atime changes roll any history. 1811.Pp 1812In order to avoid unnecessary copying it is recommended that you use 1813.Nm cpdup 1814.Fl VV 1815.Fl v 1816when doing the copyback. 1817Also make sure you traverse the snapshot softlink by appending a ".", 1818as in "<snapshotpath>/.", and you match up the directory properly. 1819.Sh RESTORING A PFS FROM A MIRROR 1820A PFS can be restored from a mirror with 1821.Cm mirror-copy . 1822.Cm config 1823data must be copied separately. 1824At last the PFS can be upgraded to master using 1825.Cm pfs-upgrade . 1826.Pp 1827It is not possible to restore the root PFS (PFS# 0) by using mirroring, 1828as the root PFS is always a master PFS. 1829A normal copy (e.g.\& using 1830.Xr cpdup 1 ) 1831must be done, ignoring history. 1832If history is important, old root PFS can me restored to a new PFS, and 1833important directories/files can be 1834.Nm null 1835mounted to the new PFS. 1836.Sh ENVIRONMENT 1837The following environment variables affect the execution of 1838.Nm : 1839.Bl -tag -width ".Ev EDITOR" 1840.It Ev EDITOR 1841The editor program specified in the variable 1842.Ev EDITOR 1843will be invoked instead of the default editor, which is 1844.Xr vi 1 . 1845.It Ev HAMMER_RSH 1846The command specified in the variable 1847.Ev HAMMER_RSH 1848will be used to initiate remote operations for the mirror-copy and 1849mirror-stream commands instead of the default command, which is 1850.Xr ssh 1 . 1851The program will be invoked via 1852.Xr execvp 3 1853using a typical 1854.Xr rsh 1 1855style 1856.Cm -l user host <remote-command> 1857command line. 1858.It Ev VISUAL 1859Same effect as 1860.Ev EDITOR 1861variable. 1862.El 1863.Sh FILES 1864.Bl -tag -width ".It Pa <fs>/var/slaves/<name>" -compact 1865.It Pa <pfs>/snapshots 1866default per PFS snapshots directory 1867.Nm ( HAMMER 1868VERSION 2-) 1869.It Pa /var/hammer/<pfs> 1870default per PFS snapshots directory (not root) 1871.Nm ( HAMMER 1872VERSION 3+) 1873.It Pa /var/hammer/root 1874default snapshots directory for root directory 1875.Nm ( HAMMER 1876VERSION 3+) 1877.It Pa <snapshots>/config 1878per PFS 1879.Nm 1880.Cm cleanup 1881configuration file 1882.Nm ( HAMMER 1883VERSION 2-) 1884.It Pa <fs>/var/slaves/<name> 1885recommended slave PFS snapshots directory 1886.Nm ( HAMMER 1887VERSION 2-) 1888.It Pa <fs>/pfs 1889recommended PFS directory 1890.El 1891.Sh EXIT STATUS 1892.Ex -std 1893.Sh SEE ALSO 1894.Xr ssh 1 , 1895.Xr undo 1 , 1896.Xr HAMMER 5 , 1897.Xr periodic.conf 5 , 1898.Xr loader 8 , 1899.Xr mount_hammer 8 , 1900.Xr mount_null 8 , 1901.Xr newfs_hammer 8 , 1902.Xr swapcache 8 , 1903.Xr sysctl 8 1904.Sh HISTORY 1905The 1906.Nm 1907utility first appeared in 1908.Dx 1.11 . 1909.Sh AUTHORS 1910.An Matthew Dillon Aq Mt dillon@backplane.com 1911