1guestmount(1)               Virtualization Support               guestmount(1)
2
3
4

NAME

6       guestmount - Mount a guest filesystem on the host using FUSE and
7       libguestfs
8

SYNOPSIS

10        guestmount [--options] -a disk.img -m device [--ro] mountpoint
11
12        guestmount [--options] -a disk.img -i [--ro] mountpoint
13
14        guestmount [--options] -d Guest -i [--ro] mountpoint
15

WARNING

17       Using "guestmount" in write mode on live virtual machines, or
18       concurrently with other disk editing tools, can be dangerous,
19       potentially causing disk corruption.  The virtual machine must be shut
20       down before you use this command, and disk images must not be edited
21       concurrently.
22
23       Use the --ro (read-only) option to use "guestmount" safely if the disk
24       image or virtual machine might be live.  You may see strange or
25       inconsistent results if running concurrently with other changes, but
26       with this option you won't risk disk corruption.
27

DESCRIPTION

29       The guestmount program can be used to mount virtual machine filesystems
30       and other disk images on the host.  It uses libguestfs for access to
31       the guest filesystem, and FUSE (the "filesystem in userspace") to make
32       it appear as a mountable device.
33
34       Along with other options, you have to give at least one device (-a
35       option) or libvirt domain (-d option), and at least one mountpoint (-m
36       option) or use the -i inspection option or the --live option.  How this
37       works is better explained in the guestfish(1) manual page, or by
38       looking at the examples below.
39
40       FUSE lets you mount filesystems as non-root.  The mountpoint must be
41       owned by you.  The filesystem will not be visible to any other users
42       unless you make configuration changes, see "NOTES" below.
43
44       To unmount the filesystem, use the guestunmount(1) command.
45

EXAMPLES

47       For a typical Windows guest which has its main filesystem on the first
48       partition:
49
50        guestmount -a windows.img -m /dev/sda1 --ro /mnt
51
52       For a typical Linux guest which has a /boot filesystem on the first
53       partition, and the root filesystem on a logical volume:
54
55        guestmount -a linux.img -m /dev/VG/LV -m /dev/sda1:/boot --ro /mnt
56
57       To get libguestfs to detect guest mountpoints for you:
58
59        guestmount -a guest.img -i --ro /mnt
60
61       For a libvirt guest called "Guest" you could do:
62
63        guestmount -d Guest -i --ro /mnt
64
65       If you don’t know what filesystems are contained in a guest or disk
66       image, use virt-filesystems(1) first:
67
68        virt-filesystems -d MyGuest
69
70       If you want to trace the libguestfs calls but without excessive
71       debugging information, we recommend:
72
73        guestmount [...] --trace /mnt
74
75       If you want to debug the program, we recommend:
76
77        guestmount [...] --trace --verbose /mnt
78
79       To unmount the filesystem after using it:
80
81        guestunmount /mnt
82

NOTES

84   Other users cannot see the filesystem by default
85       If you mount a filesystem as one user (eg. root), then other users will
86       not be able to see it by default.  The fix is to add the FUSE
87       "allow_other" option when mounting:
88
89        sudo guestmount [...] -o allow_other /mnt
90
91       and to enable this option in /etc/fuse.conf.
92
93   Enabling FUSE
94       On some distros, you may need to add yourself to a special group (eg.
95       "fuse") before you can use any FUSE filesystem.  This is necessary on
96       Debian and derivatives.
97
98       On other distros, no special group is required.  It is not necessary on
99       Fedora or Red Hat Enterprise Linux.
100
101   fusermount error: "Device or resource busy"
102       You can see this error when another process on the system jumps into
103       the mountpoint you have just created, holding it open and preventing
104       you from unmounting it.  The usual culprits are various GUI "indexing"
105       programs.
106
107       The popular workaround for this problem is to retry the "fusermount -u"
108       command a few times until it works (guestunmount(1) does this for you).
109       Unfortunately this isn't a reliable fix if (for example) the mounted
110       filesystem is particularly large and the intruding program particularly
111       persistent.
112
113       A proper fix is to use a private mountpoint by creating a new mount
114       namespace using the Linux-specific clone(2)/unshare(2) flag
115       "CLONE_NEWNS".  Unfortunately at the moment this requires root and we
116       would also probably need to add it as a feature to guestmount.
117
118   Race conditions possible when shutting down the connection
119       When guestunmount(1)/fusermount(1) exits, guestmount may still be
120       running and cleaning up the mountpoint.  The disk image will not be
121       fully finalized.
122
123       This means that scripts like the following have a nasty race condition:
124
125        guestmount -a disk.img -i /mnt
126        # copy things into /mnt
127        guestunmount /mnt
128        # immediately try to use 'disk.img' ** UNSAFE **
129
130       The solution is to use the --pid-file option to write the guestmount
131       PID to a file, then after guestunmount spin waiting for this PID to
132       exit.
133
134        guestmount -a disk.img -i --pid-file guestmount.pid /mnt
135
136        # ...
137        # ...
138
139        # Save the PID of guestmount *before* calling guestunmount.
140        pid="$(cat guestmount.pid)"
141
142        # Unmount the filesystem.
143        guestunmount /mnt
144
145        timeout=10
146
147        count=$timeout
148        while kill -0 "$pid" 2>/dev/null && [ $count -gt 0 ]; do
149            sleep 1
150            ((count--))
151        done
152        if [ $count -eq 0 ]; then
153            echo "$0: wait for guestmount to exit failed after $timeout seconds"
154            exit 1
155        fi
156
157        # Now it is safe to use the disk image.
158
159       Note that if you use the "guestfs_mount_local" API directly (see "MOUNT
160       LOCAL" in guestfs(3)) then it is much easier to write a safe, race-free
161       program.
162

OPTIONS

164       -a IMAGE
165       --add IMAGE
166           Add a block device or virtual machine image.
167
168           The format of the disk image is auto-detected.  To override this
169           and force a particular format use the --format=.. option.
170
171       -a URI
172       --add URI
173           Add a remote disk.  See "ADDING REMOTE STORAGE" in guestfish(1).
174
175       -c URI
176       --connect URI
177           When used in conjunction with the -d option, this specifies the
178           libvirt URI to use.  The default is to use the default libvirt
179           connection.
180
181       -d LIBVIRT-DOMAIN
182       --domain LIBVIRT-DOMAIN
183           Add disks from the named libvirt domain.  If the --ro option is
184           also used, then any libvirt domain can be used.  However in write
185           mode, only libvirt domains which are shut down can be named here.
186
187           Domain UUIDs can be used instead of names.
188
189       --dir-cache-timeout N
190           Set the readdir cache timeout to N seconds, the default being 60
191           seconds.  The readdir cache [actually, there are several semi-
192           independent caches] is populated after a readdir(2) call with the
193           stat and extended attributes of the files in the directory, in
194           anticipation that they will be requested soon after.
195
196           There is also a different attribute cache implemented by FUSE (see
197           the FUSE option -o attr_timeout), but the FUSE cache does not
198           anticipate future requests, only cache existing ones.
199
200       --echo-keys
201           When prompting for keys and passphrases, guestfish normally turns
202           echoing off so you cannot see what you are typing.  If you are not
203           worried about Tempest attacks and there is no one else in the room
204           you can specify this flag to see what you are typing.
205
206       --fd=FD
207           Specify a pipe or eventfd file descriptor.  When the mountpoint is
208           ready to be used, guestmount writes a single byte to this file
209           descriptor.  This can be used in conjunction with --no-fork in
210           order to run guestmount captive under another process.
211
212       --format=raw|qcow2|..
213       --format
214           The default for the -a option is to auto-detect the format of the
215           disk image.  Using this forces the disk format for -a options which
216           follow on the command line.  Using --format with no argument
217           switches back to auto-detection for subsequent -a options.
218
219           If you have untrusted raw-format guest disk images, you should use
220           this option to specify the disk format.  This avoids a possible
221           security problem with malicious guests (CVE-2010-3851).  See also
222           "guestfs_add_drive_opts" in guestfs(3).
223
224       --fuse-help
225           Display help on special FUSE options (see -o below).
226
227       --help
228           Display brief help and exit.
229
230       -i
231       --inspector
232           Using virt-inspector(1) code, inspect the disks looking for an
233           operating system and mount filesystems as they would be mounted on
234           the real virtual machine.
235
236       --key SELECTOR
237           Specify a key for LUKS, to automatically open a LUKS device when
238           using the inspection.  "SELECTOR" can be in one of the following
239           formats:
240
241           --key "DEVICE":key:KEY_STRING
242               Use the specified "KEY_STRING" as passphrase.
243
244           --key "DEVICE":file:FILENAME
245               Read the passphrase from FILENAME.
246
247       --keys-from-stdin
248           Read key or passphrase parameters from stdin.  The default is to
249           try to read passphrases from the user by opening /dev/tty.
250
251       --live
252           Connect to a live virtual machine.  (Experimental, see "ATTACHING
253           TO RUNNING DAEMONS" in guestfs(3)).
254
255       -m dev[:mountpoint[:options[:fstype]]
256       --mount dev[:mountpoint[:options[:fstype]]]
257           Mount the named partition or logical volume on the given mountpoint
258           in the guest (this has nothing to do with mountpoints in the host).
259
260           If the mountpoint is omitted, it defaults to /.  You have to mount
261           something on /.
262
263           The third (and rarely used) part of the mount parameter is the list
264           of mount options used to mount the underlying filesystem.  If this
265           is not given, then the mount options are either the empty string or
266           "ro" (the latter if the --ro flag is used).  By specifying the
267           mount options, you override this default choice.  Probably the only
268           time you would use this is to enable ACLs and/or extended
269           attributes if the filesystem can support them:
270
271            -m /dev/sda1:/:acl,user_xattr
272
273           The fourth part of the parameter is the filesystem driver to use,
274           such as "ext3" or "ntfs". This is rarely needed, but can be useful
275           if multiple drivers are valid for a filesystem (eg: "ext2" and
276           "ext3"), or if libguestfs misidentifies a filesystem.
277
278       --no-fork
279           Don’t daemonize (or fork into the background).
280
281       -n
282       --no-sync
283           By default, we attempt to sync the guest disk when the FUSE
284           mountpoint is unmounted.  If you specify this option, then we don't
285           attempt to sync the disk.  See the discussion of autosync in the
286           guestfs(3) manpage.
287
288       -o OPTION
289       --option OPTION
290           Pass extra options to FUSE.
291
292           To get a list of all the extra options supported by FUSE, use the
293           command below.  Note that only the FUSE -o options can be passed,
294           and only some of them are a good idea.
295
296            guestmount --fuse-help
297
298           Some potentially useful FUSE options:
299
300           -o allow_other
301               Allow other users to see the filesystem.  This option has no
302               effect unless you enable it globally in /etc/fuse.conf.
303
304           -o attr_timeout=N
305               Enable attribute caching by FUSE, and set the timeout to N
306               seconds.
307
308           -o kernel_cache
309               Allow the kernel to cache files (reduces the number of reads
310               that have to go through the guestfs(3) API).  This is generally
311               a good idea if you can afford the extra memory usage.
312
313           -o uid=N -o gid=N
314               Use these options to map all UIDs and GIDs inside the guest
315               filesystem to the chosen values.
316
317           -o use_ino
318               Preserve inode numbers from the underlying filesystem.
319
320               Without this option, FUSE makes up its own inode numbers.  The
321               inode numbers you see in stat(2), "ls -i" etc aren't the inode
322               numbers of the underlying filesystem.
323
324               Note this option is potentially dangerous if the underlying
325               filesystem consists of multiple mountpoints, as you may see
326               duplicate inode numbers appearing through FUSE.  Use of this
327               option can confuse some software.
328
329       --pid-file FILENAME
330           Write the PID of the guestmount worker process to "filename".
331
332       -r
333       --ro
334           Add devices and mount everything read-only.  Also disallow writes
335           and make the disk appear read-only to FUSE.
336
337           This is highly recommended if you are not going to edit the guest
338           disk.  If the guest is running and this option is not supplied,
339           then there is a strong risk of disk corruption in the guest.  We
340           try to prevent this from happening, but it is not always possible.
341
342           See also "OPENING DISKS FOR READ AND WRITE" in guestfish(1).
343
344       --selinux
345           This option is provided for backwards compatibility and does
346           nothing.
347
348       -v
349       --verbose
350           Enable verbose messages from underlying libguestfs.
351
352       -V
353       --version
354           Display the program version and exit.
355
356       -w
357       --rw
358           This changes the -a, -d and -m options so that disks are added and
359           mounts are done read-write.
360
361           See "OPENING DISKS FOR READ AND WRITE" in guestfish(1).
362
363       -x
364       --trace
365           Trace libguestfs calls and entry into each FUSE function.
366
367           This also stops the daemon from forking into the background (see
368           --no-fork).
369

FILES

371       $XDG_CONFIG_HOME/libguestfs/libguestfs-tools.conf
372       $HOME/.libguestfs-tools.rc
373       $XDG_CONFIG_DIRS/libguestfs/libguestfs-tools.conf
374       /etc/libguestfs-tools.conf
375           This configuration file controls the default read-only or read-
376           write mode (--ro or --rw).
377
378           See libguestfs-tools.conf(5).
379

EXIT STATUS

381       This program returns 0 if successful, or non-zero if there was an
382       error.
383

SEE ALSO

385       guestunmount(1), fusermount(1), guestfish(1), virt-inspector(1),
386       virt-cat(1), virt-edit(1), virt-tar(1), libguestfs-tools.conf(5),
387       "MOUNT LOCAL" in guestfs(3), http://libguestfs.org/,
388       http://fuse.sf.net/.
389

AUTHORS

391       Richard W.M. Jones ("rjones at redhat dot com")
392
394       Copyright (C) 2009-2019 Red Hat Inc.
395

LICENSE

397       This program is free software; you can redistribute it and/or modify it
398       under the terms of the GNU General Public License as published by the
399       Free Software Foundation; either version 2 of the License, or (at your
400       option) any later version.
401
402       This program is distributed in the hope that it will be useful, but
403       WITHOUT ANY WARRANTY; without even the implied warranty of
404       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
405       General Public License for more details.
406
407       You should have received a copy of the GNU General Public License along
408       with this program; if not, write to the Free Software Foundation, Inc.,
409       51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
410

BUGS

412       To get a list of bugs against libguestfs, use this link:
413       https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
414
415       To report a new bug against libguestfs, use this link:
416       https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
417
418       When reporting a bug, please supply:
419
420       ·   The version of libguestfs.
421
422       ·   Where you got libguestfs (eg. which Linux distro, compiled from
423           source, etc)
424
425       ·   Describe the bug accurately and give a way to reproduce it.
426
427       ·   Run libguestfs-test-tool(1) and paste the complete, unedited output
428           into the bug report.
429
430
431
432libguestfs-1.40.1                 2019-01-17                     guestmount(1)
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