misc-utils/wipefs.8

   1 .\" Copyright 2009 by Karel Zak.  All Rights Reserved.
   2 .\" This file may be copied under the terms of the GNU Public License.
   3 .\"
   4 .TH WIPEFS 8 "December 2014" "util-linux" "System Administration"
   5 .SH NAME
   6 wipefs \- wipe a signature from a device
   7 .SH SYNOPSIS
   8 .B wipefs
   9 .RB [ options ]
  10 .IR device ...
  11 .sp
  12 .B wipefs
  13 .RB [ \-\-backup ]
  14 .B \-o
  15 .I offset
  16 .IR device ...
  17 .sp
  18 .B wipefs
  19 .RB [ \-\-backup ]
  20 .B \-a
  21 .IR device ...
  22 .SH DESCRIPTION
  23 .B wipefs
  24 can erase filesystem, raid or partition-table signatures (magic strings) from
  25 the specified
  26 .I device
  27 to make the signatures invisible for libblkid.
  28 .B wipefs
  29 does not erase the filesystem itself nor any other data from the device.
  30
  31 When used without any options, wipefs lists all visible filesystems and the
  32 offsets of their basic signatures.  The default output is subject to change.
  33 So whenever possible, you should avoid using default outputs in your scripts.
  34 Always explicitly define expected columns by using
  35 .B \-\-output
  36 .I columns-list
  37 in environments where a stable output is required.
  38
  39 .B wipefs
  40 calls the BLKRRPART ioctl when it has erased a partition-table signature
  41 to inform the kernel about the change. The ioctl is called as the last step
  42 and when all specified signatures from all specified devices are already erased.
  43
  44 Note that some filesystems and some partition tables store more magic strings on
  45 the device (e.g., FAT, ZFS, GPT).  The
  46 .B wipefs
  47 command (since v2.31) lists all the offset where a magic strings have been
  48 detected.
  49
  50 When option \fB\-a\fR is used, all magic strings that are visible for libblkid are
  51 erased. In this case the
  52 .B wipefs
  53 scans the device again after each modification (erase) until no magic string is found.
  54
  55 Note that by default
  56 .B wipefs
  57 does not erase nested partition tables on non-whole disk devices.
  58 For this the option \fB\-\-force\fR is required.
  59
  60 .SH OPTIONS
  61 .TP
  62 .BR \-a , " \-\-all"
  63 Erase all available signatures.  The set of erased signatures can be
  64 restricted with the \fB\-t\fR option.
  65 .TP
  66 .BR \-b , " \-\-backup"
  67 Create a signature backup to the file $HOME/wipefs-<devname>-<offset>.bak.
  68 For more details see the \fBEXAMPLE\fR section.
  69 .TP
  70 .BR \-f , " \-\-force"
  71 Force erasure, even if the filesystem is mounted.  This is required in
  72 order to erase a partition-table signature on a block device.
  73 .TP
  74 .BR \-h , " \-\-help"
  75 Display help text and exit.
  76 .TP
  77 .BR \-J , " \-\-json"
  78 Use JSON output format.
  79 .TP
  80 \fB\-\-lock\fR[=\fImode\fR]
  81 Use exclusive BSD lock for device or file it operates.  The optional argument
  82 \fImode\fP can be \fByes\fR, \fBno\fR (or 1 and 0) or \fBnonblock\fR.  If the \fImode\fR
  83 argument is omitted, it defaults to \fB"yes"\fR.  This option overwrites
  84 environment variable \fB$LOCK_BLOCK_DEVICE\fR.  The default is not to use any
  85 lock at all, but it's recommended to avoid collisions with udevd or other
  86 tools.
  87 .TP
  88 .BR \-i , " \-\-noheadings"
  89 Do not print a header line.
  90 .TP
  91 .BR \-O , " \-\-output " \fIlist\fP
  92 Specify which output columns to print.  Use \-\-help to
  93 get a list of all supported columns.
  94 .TP
  95 .BR \-n , " \-\-no\-act"
  96 Causes everything to be done except for the write() call.
  97 .TP
  98 .BR \-o , " \-\-offset " \fIoffset\fP
  99 Specify the location (in bytes) of the signature which should be erased from the
 100 device.  The \fIoffset\fR number may include a "0x" prefix; then the number will be
 101 interpreted as a hex value.  It is possible to specify multiple \fB\-o\fR options.
 102 .sp
 103 The \fIoffset\fR argument may be followed by the multiplicative
 104 suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB
 105 (the "iB" is optional, e.g., "K" has the same meaning as "KiB"), or the suffixes
 106 KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
 107 .TP
 108 .BR \-p , " \-\-parsable"
 109 Print out in parsable instead of printable format.  Encode all potentially unsafe
 110 characters of a string to the corresponding hex value prefixed by '\\x'.
 111 .TP
 112 .BR \-q , " \-\-quiet"
 113 Suppress any messages after a successful signature wipe.
 114 .TP
 115 .BR \-t , " \-\-types " \fIlist\fP
 116 Limit the set of printed or erased signatures.  More than one type may
 117 be specified in a comma-separated list.  The list or individual types
 118 can be prefixed with 'no' to specify the types on which no action should be
 119 taken.  For more details see mount(8).
 120 .TP
 121 .BR \-V , " \-\-version"
 122 Display version information and exit.
 123 .SH ENVIRONMENT
 124 .IP LIBBLKID_DEBUG=all
 125 enables libblkid debug output.
 126 .IP LOCK_BLOCK_DEVICE=<mode>
 127 use exclusive BSD lock.  The mode is "1" or "0".  See \fB\-\-lock\fR for more details.
 128 .SH EXAMPLE
 129 .TP
 130 .B wipefs /dev/sda*
 131 Prints information about sda and all partitions on sda.
 132 .TP
 133 .B wipefs \-\-all \-\-backup /dev/sdb
 134 Erases all signatures from the device /dev/sdb and creates a signature backup
 135 file ~/wipefs-sdb-<offset>.bak for each signature.
 136 .TP
 137 .B dd if=~/wipefs-sdb-0x00000438.bak of=/dev/sdb seek=$((0x00000438)) bs=1 conv=notrunc
 138 Restores an ext2 signature from the backup file  ~/wipefs-sdb-0x00000438.bak.
 139 .SH AUTHORS
 140 Karel Zak <kzak@redhat.com>
 141 .SH SEE ALSO
 142 .BR blkid (8),
 143 .BR findfs (8)
 144 .SH AVAILABILITY
 145 The wipefs command is part of the util-linux package and is available from
 146 https://www.kernel.org/pub/linux/utils/util-linux/.