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)