zhack.1

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