zhack

ZHACK(1) General Commands Manual ZHACK(1)

NAME

   zhack  libzpool debugging tool

DESCRIPTION

   This utility pokes configuration changes directly into a ZFS pool, which is dangerous and can cause data corruption.

SYNOPSIS

    zhack       feature stat       pool
           List feature flags.

    zhack feature enable [-d description] [-r] pool guid
           Add a new feature to pool that is uniquely identified by guid, which is specified in the same form as a zfs(8) user property.

           The description is a short human readable explanation of the new feature.

           The -r flag indicates that pool can be safely opened in read-only mode by a system that does not understand the guid feature.

    zhack feature ref [-d|-m] pool guid
           Increment the reference count of the guid feature in pool.

           The -d flag decrements the reference count of the guid feature in pool instead.

           The -m flag indicates that the guid feature is now required to read the pool MOS.

    zhack label repair [-cu] device
           Repair labels of a specified device according to options.

           Flags may be combined to do their functions simultaneously.

           The -c flag repairs corrupted label checksums

           The -u flag restores the label on a detached device

           Example:
     zhack label repair -cu device
             Fix checksums and undetach a device

GLOBAL OPTIONS

   The following can be passed to all zhack invocations before any subcommand:

   -c cachefile
           Read pool configuration from the cachefile, which is /etc/zfs/zpool.cache by default.

   -d dir  Search for pool members in dir.  Can be specified more than once.

EXAMPLES

   # zhack feature stat 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.

   # zhack feature enable -d 'Predict future disk failures.' tank com.example:clairvoyance
   # zhack feature ref tank com.example:clairvoyance

SEE ALSO

   ztest(1), zpool-features(7), zfs(8)

OpenZFS May 26, 2021 ZHACK(1)