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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 fea-
	       ture.

	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 subcom-
       mand:

       -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)

FreeBSD	Ports 14.quarterly	 May 26, 2021			      ZHACK(1)

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