zhack.1

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 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.

The following can be passed to all zhack invocations before any subcommand:
cachefile
Read pool configuration from the cachefile, which is /etc/zfs/zpool.cache by default.
dir
Search for pool members in dir. Can be specified more than once.

# 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

ztest(1), zpool-features(7), zfs(8)
May 26, 2021 Debian