Man page - zhack(1)

Manual

---

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)

---