ZHACK(1) General Commands Manual ZHACK(1)

zhack - libzpool debugging tool

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

zhack [-c cachefile] [-d dir] <subcommand> [arguments]

-c cachefile
Read the pool configuration from the cachefile, which is /etc/zfs/zpool.cache by default.
-d dir
Search for pool members in the dir path. Can be specified more than once.

feature stat pool
List feature flags.
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 switch indicates that pool can be safely opened in read-only mode by a system that does not have the guid feature.
feature ref [-d|-m] pool guid
Increment the reference count of the guid feature in pool.
The -d switch decrements the reference count of the guid feature in pool.
The -m switch indicates that the guid feature is now required to read the pool MOS.

# 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

This man page was written by Darik Horn <dajhorn@vanadac.com>.

zfs(8), zpool-features(5), ztest(1)
August 24, 2020 OpenZFS