* Remove empty lines and trailing whitespace.

[dragonfly.git] / sbin / hammer / hammer.8

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.\" by Matthew Dillon <dillon@backplane.com>
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.\" $DragonFly: src/sbin/hammer/hammer.8,v 1.27 2008/06/28 14:23:59 swildner Exp $
.Dd June 26, 2008
.Dt HAMMER 8
.Os
.Sh NAME
.Nm hammer
.Nd HAMMER file system utility
.Sh SYNOPSIS
.Nm
.Op Fl hrx
.Op Fl c Ar cyclefile
.Op Fl f Ar blkdev[:blkdev]*
.Op Fl s Ar linkpath
.Op Fl t Ar timeout
.Ar command
.Ar ...
.Sh DESCRIPTION
The
.Nm
utility provides miscellaneous functions related to managing a HAMMER
filesystem.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl h
Get help
.It Fl r
Specify recursion for those commands which support it.
.It Fl c Ar cyclefile
When pruning and reblocking you can instruction HAMMER to start at the
object id stored in the specified file.  If the file does not exist
HAMMER will start at the beginning.  If HAMMER is told to run for a
specific period of time and is unable to complete the operation it will
write out the current obj_id so the next run can pick up where it left
off.  If HAMMER runs to completion it will delete the cyclefile..
.It Fl f Ar blkdev[:blkdev]*
Specify the volumes making up a HAMMER filesystem.
.It Fl s Ar linkpath
When pruning a filesystem you can instruct HAMMER to create softlinks
to available snapshots.
.It Fl t Ar timeout
When pruning and reblocking you can tell the utility to stop after a
certain period of time.  This option is used along with the cycle file
option to prune or reblock a portion of the filesystem incrementally.
.It Fl v
Increase verboseness.  May be specified multiple times.
.El
.Pp
The commands are as follows:
.Bl -tag -width indent
.It Ar synctid Ar filesystem Op quick
Generates a guaranteed, formal 64 bit transaction id representing the
current state of the specified HAMMER filesystem.  The filesystem will
be synced to the media.
.Pp
If the
.Ar quick
keyword is specified the filesystem will be soft-synced, meaning that a
crash might still undo the state of the filesystem as of the transaction
id returned but any new modifications will occur after the returned
transaction id as expected.
.It Ar bstats Op interval
Output HAMMER B-Tree statistics until interrupted.  The default interval
is one second.
.It Ar iostats Op interval
Output HAMMER I/O statistics until interrupted.  The default interval
is one second.
.It Ar history Ar path
Show the modification history for a HAMMER file's inode and data.
.It Ar show Op vol_no[:clu_no]
Dump the B-Tree starting at the specified volume and cluster, or
at the root volume if not specified.
The B-Tree is dumped recursively if the
.Fl r
option is specified.
.It Ar blockmap
Dump the btree, record, large-data, and small-data blockmaps, showing
physical block assignments and free space percentages.
.It Ar namekey Ar filename
Generate a HAMMER 64 bit directory hash for the specified file name.
The low 32 bits are used as an iterator for hash collisions and will be
output as 0.
.It Ar namekey32 Ar filename
Generate the top 32 bits of a HAMMER 64 bit directory hash for the specified
file name.
.It Ar prune Ar softlink-dir
Prune the filesystem based on previously created snapshot softlinks.
The target directory is expected to contain softlinks pointing to
snapshots of the filesystems you wish to retain.  The directory is scanned
non-recursively and the mount points and transaction ids stored in the
softlinks are extracted and sorted.
The filesystem is then explicitly pruned according to what is found.
Cleaning out portions of the filesystem is as simple as removing a softlink
and then running the
.Ar prune
command.
.Pp
As a safety measure pruning only occurs if one or more softlinks are found
containing the @@ snapshot id extension.
.Pp
Currently the scanned softlink directory must contain softlinks pointing
to a single HAMMER mount.  The softlinks may specify absolute or relative
paths.  Softlinks must use 20-character (@@0x%016llx) transaction ids,
as might be returned from 'hammer synctid <filesystem>'.
.Pp
Example, lets say your snapshot directory contains the following links:
.Pp
.Li "lrwxr-xr-x  1 root  wheel  29 May 31 17:57 snap1 -> /usr/obj/@@0x10d2cd05b7270d16"
.Pp
.Li "lrwxr-xr-x  1 root  wheel  29 May 31 17:58 snap2 -> /usr/obj/@@0x10d2cd13f3fde98f"
.Pp
.Li "lrwxr-xr-x  1 root  wheel  29 May 31 17:59 snap3 -> /usr/obj/@@0x10d2cd222adee364"
.Pp
If you were to run the prune command on this directory, then the HAMMER
/usr/obj mount will be pruned to retain the above three snapshots.
In addition, modifications made to the filesystem older then the oldest
snapshot will be destroyed and potentially fine-grained modifications made
to the filesystem more recently then the most recent snapshot will be
retained.
.Pp
If you then delete the snap2 softlink and rerun the prune command,
modifications pertaining to that snapshot would be destroyed.
.It Ar prune-everything Ar filesystem
This command will remove all historical records from the filesystem.
This directive is not normally used on a production system.
.Pp
Note that pruning a filesystem may not immediately free-up space,
though typically some space will be freed if a large number of records are
pruned out.  The filesystem must be reblocked to completely recover all
available space.
.It Ar snapshot Ar snapshot-dir
.It Ar snapshot Ar filesystem snapshot-dir
Takes a snapshot of the filesystem either explicitly given by
.Ar filesystem
or implicitly derived from the
.Ar snapshot-dir
argument and creates a symlink in the directory provided by
.Ar snapshot-dir
pointing to the snapshot.
If
.Ar snapshot-dir
is no directory, it is assumed to be a format string
passed to strftime(3) with the current time as parameter.
If
.Ar snapshot-dir
refers to an existing directory, a default format string of "snap-%Y%d%m-%H%M"
is assumed and used as name for the newly created symlink.
Assuming that "/mysnapshots" is on filesystem "/" and that "/obj" is a
filesystem on its own, the following invocations:
.Li hammer snapshot /mysnapshots
.Li hammer snapshot /mysnapshots/%Y-%m-%d
.Li hammer snapshot /obj /mysnapshots/obj-%Y-%m-%d
would create symlinks similar to:
.Li /mysnapshots/snap-20080627-1210 -> /@@0x10d2cd05b7270d16
.Li /mysnapshots/2008-06-27 -> /@@0x10d2cd05b7270d16
.Li /mysnapshots/obj-2008-06-27 -> /obj@@0x10d2cd05b7270d16
.It Ar reblock Ar filesystem Op Ar fill_percentage
.It Ar reblock-btree Ar filesystem Op Ar fill_percentage
.It Ar reblock-inodes Ar filesystem Op Ar fill_percentage
.It Ar reblock-dirs Ar filesystem Op Ar fill_percentage
.It Ar reblock-data Ar filesystem Op Ar fill_percentage
Attempt to defragment and free space for reuse by reblocking a live
HAMMER filesystem.
Big blocks cannot be reused by HAMMER until they are completely free.
This command also has the effect of reordering all elements, effectively
defragmenting the filesystem.
.Pp
The default fill percentage is 100% and will cause the filesystem to be
completely defragmented.  All specified element types will be reallocated
and rewritten.  If you wish to quickly free up space instead try specifying
a smaller fill percentage, such as 90% or 80% (the '%' suffix is not needed).
.Pp
Since this command may rewrite the entire contents of the disk it is
best to do it incrementally from a cron job along with the
.Fl c Ar cyclefile
and
.Fl t Ar timeout
options to limit the run time.
The filesystem would thus be defragmented over long period of time.
.Pp
It is recommended that separate invocations be used for each data type.
Btree nodes, inodes, and directories are typically the most important
elements needing defragmentation.  Data can be defragmented over a longer
period of time.
.It Ar pseudofs Ar dirpath
Create a pseudo-filesystem inside a HAMMER filesystem.  Up to 65535 such
filesystems can be created.  Each one uses an independant inode numbering
space making it suitable for use as a replication source or target.
.El
.Sh EXAMPLES
.Sh DIAGNOSTICS
Exit status is 0 on success and 1 on error.
.Sh SEE ALSO
.Xr newfs_hammer 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Dx 1.11 .
.Sh AUTHORS
.An Matthew Dillon Aq dillon@backplane.com