FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/man/man1/zhack.1

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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
   .Ar device
   .Xc
   Repair corrupted labels by rewriting the checksum using the presumed valid
   contents of the label.
   .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

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