mirror_zfs/man/man1/zhack.1
buzzingwires a46001adb9
Allow zhack label repair to restore detached devices.
This commit expands on the zhack label repair command in d04b5c9 by
adding the -u option to undetach a device by regenerating uberblocks,
in addition to the existing functionality of fixing checksums, now
represented by -c. Previous behavior is retained in the case of no
options.

The changes are heavily inspired by Jeff Bonwick's labelfix
utility, as archived at:

https://gist.github.com/jjwhitney/baaa63144da89726e482

Additionally, it is now capable of properly determining the size of
block devices and other media, as well as handling sizes which are
not divisible by 2^18. This should make it viable for use on physical
devices and partitions, in addition to files.

These changes should make it possible to import zpools that have had
their uberblocks erased, such as in the case of pools rendered
inaccessible by erroneous detach commands.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: buzzingwires <buzzingwires@outlook.com>
Closes #14773
2023-05-03 09:03:57 -07:00

168 lines
3.4 KiB
Groff

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.\" Copyright 2013 Darik Horn <dajhorn@vanadac.com>. All rights reserved.
.\"
.\" lint-ok: WARNING: sections out of conventional order: Sh SYNOPSIS
.\"
.Dd May 26, 2021
.Dt ZHACK 1
.Os
.
.Sh NAME
.Nm zhack
.Nd libzpool debugging tool
.Sh DESCRIPTION
This utility pokes configuration changes directly into a ZFS pool,
which is dangerous and can cause data corruption.
.Sh SYNOPSIS
.Bl -tag -width Ds
.It Xo
.Nm zhack
.Cm feature stat
.Ar pool
.Xc
List feature flags.
.
.It Xo
.Nm zhack
.Cm feature enable
.Op Fl d Ar description
.Op Fl r
.Ar pool
.Ar guid
.Xc
Add a new feature to
.Ar pool
that is uniquely identified by
.Ar guid ,
which is specified in the same form as a
.Xr zfs 8
user property.
.Pp
The
.Ar description
is a short human readable explanation of the new feature.
.Pp
The
.Fl r
flag indicates that
.Ar pool
can be safely opened in read-only mode by a system that does not understand the
.Ar guid
feature.
.
.It Xo
.Nm zhack
.Cm feature ref
.Op Fl d Ns | Ns Fl m
.Ar pool
.Ar guid
.Xc
Increment the reference count of the
.Ar guid
feature in
.Ar pool .
.Pp
The
.Fl d
flag decrements the reference count of the
.Ar guid
feature in
.Ar pool
instead.
.Pp
The
.Fl m
flag indicates that the
.Ar guid
feature is now required to read the pool MOS.
.
.It Xo
.Nm zhack
.Cm label repair
.Op Fl cu
.Ar device
.Xc
Repair labels of a specified
.Ar device
according to options.
.Pp
Flags may be combined to do their functions simultaneously.
.
.Pp
The
.Fl c
flag repairs corrupted label checksums
.
.Pp
The
.Fl u
flag restores the label on a detached device
.Pp
Example:
.Nm zhack Cm label repair Fl cu Ar device
Fix checksums and undetach a device
.
.El
.
.Sh GLOBAL OPTIONS
The following can be passed to all
.Nm
invocations before any subcommand:
.Bl -tag -width "-d dir"
.It Fl c Ar cachefile
Read
.Ar pool
configuration from the
.Ar cachefile ,
which is
.Pa /etc/zfs/zpool.cache
by default.
.It Fl d Ar dir
Search for
.Ar pool
members in
.Ar dir .
Can be specified more than once.
.El
.
.Sh EXAMPLES
.Bd -literal
.No # Nm zhack Cm feature stat Ar tank
for_read_obj:
org.illumos:lz4_compress = 0
for_write_obj:
com.delphix:async_destroy = 0
com.delphix:empty_bpobj = 0
descriptions_obj:
com.delphix:async_destroy = Destroy filesystems asynchronously.
com.delphix:empty_bpobj = Snapshots use less space.
org.illumos:lz4_compress = LZ4 compression algorithm support.
.No # Nm zhack Cm feature enable Fl d No 'Predict future disk failures.' Ar tank com.example:clairvoyance
.No # Nm zhack Cm feature ref Ar tank com.example:clairvoyance
.Ed
.
.Sh SEE ALSO
.Xr ztest 1 ,
.Xr zpool-features 7 ,
.Xr zfs 8