virt-edit(1) Virtualization Support virt-edit(1)NAMEvirt-edit - Edit a file in a virtual machine
SYNOPSISvirt-edit [--options] -d domname file [file ...]
virt-edit [--options] -a disk.img [-a disk.img ...] file [file ...]
virt-edit [-d domname|-a disk.img] file -e 'expr'
Old-style:
virt-edit domname file
virt-edit disk.img [disk.img ...] file
WARNING
You must not use "virt-edit" on live virtual machines. If you do this,
you risk disk corruption in the VM. "virt-edit" tries to stop you from
doing this, but doesn't catch all cases.
DESCRIPTION
"virt-edit" is a command line tool to edit "file" where each "file"
exists in the named virtual machine (or disk image).
Multiple filenames can be given, in which case they are each edited in
turn. Each filename must be a full path, starting at the root
directory (starting with '/').
If you want to just view a file, use virt-cat(1).
For more complex cases you should look at the guestfish(1) tool (see
"USING GUESTFISH" below).
"virt-edit" cannot be used to create a new file. guestfish(1) can do
that and much more.
EXAMPLES
Edit the named files interactively:
virt-edit-d mydomain /boot/grub/grub.conf
virt-edit-d mydomain /etc/passwd
For Windows guests, some Windows paths are understood:
virt-edit-d mywindomain 'c:\autoexec.bat'
If Perl is installed, you can also edit files non-interactively (see
"NON-INTERACTIVE EDITING" below). To change the init default level to
5:
virt-edit-d mydomain /etc/inittab -e 's/^id:.*/id:5:initdefault:/'
OPTIONS--help
Display brief help.
-a file
--add file
Add file which should be a disk image from a virtual machine. If
the virtual machine has multiple block devices, you must supply all
of them with separate -a options.
The format of the disk image is auto-detected. To override this
and force a particular format use the --format=.. option.
-b extension
--backup extension
Create a backup of the original file in the guest disk image. The
backup has the original filename with "extension" added.
Usually the first character of "extension" would be a dot "." so
you would write:
virt-edit-b .orig [etc]
By default, no backup file is made.
-c URI
--connect URI
If using libvirt, connect to the given URI. If omitted, then we
connect to the default libvirt hypervisor.
If you specify guest block devices directly, then libvirt is not
used at all.
-d guest
--domain guest
Add all the disks from the named libvirt guest. Domain UUIDs can
be used instead of names.
--echo-keys
When prompting for keys and passphrases, virt-edit normally turns
echoing off so you cannot see what you are typing. If you are not
worried about Tempest attacks and there is no one else in the room
you can specify this flag to see what you are typing.
-e EXPR
--expr EXPR
Instead of launching the external editor, non-interactively apply
the Perl expression "EXPR" to each line in the file. See "NON-
INTERACTIVE EDITING" below.
Be careful to properly quote the expression to prevent it from
being altered by the shell.
Note that this option is only available when Perl 5 is installed.
--format raw|qcow2|...
--format
The default for the -a option is to auto-detect the format of the
disk image. Using this forces the disk format for -a options which
follow on the command line. Using --format with no argument
switches back to auto-detection for subsequent -a options.
For example:
virt-edit --format=raw -a disk.img file
forces raw format (no auto-detection) for "disk.img".
virt-edit --format=raw -a disk.img --format -a another.img file
forces raw format (no auto-detection) for "disk.img" and reverts to
auto-detection for "another.img".
If you have untrusted raw-format guest disk images, you should use
this option to specify the disk format. This avoids a possible
security problem with malicious guests (CVE-2010-3851).
--keys-from-stdin
Read key or passphrase parameters from stdin. The default is to
try to read passphrases from the user by opening "/dev/tty".
-v
--verbose
Enable verbose messages for debugging.
-V
--version
Display version number and exit.
-x Enable tracing of libguestfs API calls.
OLD-STYLE COMMAND LINE ARGUMENTS
Previous versions of virt-edit allowed you to write either:
virt-edit disk.img [disk.img ...] file
or
virt-edit guestname file
whereas in this version you should use -a or -d respectively to avoid
the confusing case where a disk image might have the same name as a
guest.
For compatibility the old style is still supported.
NON-INTERACTIVE EDITING
"virt-edit" normally calls out to $EDITOR (or vi) so the system
administrator can interactively edit the file.
There are two ways also to use "virt-edit" from scripts in order to
make automated edits to files. (Note that although you can use
"virt-edit" like this, it's less error-prone to write scripts directly
using the libguestfs API and Augeas for configuration file editing.)
The first method is to temporarily set $EDITOR to any script or program
you want to run. The script is invoked as "$EDITOR tmpfile" and it
should update "tmpfile" in place however it likes.
The second method is to use the -e parameter of "virt-edit" to run a
short Perl snippet in the style of sed(1). For example to replace all
instances of "foo" with "bar" in a file:
virt-edit-d domname filename -e 's/foo/bar/'
The full power of Perl regular expressions can be used (see perlre(1)).
For example to delete root's password you could do:
virt-edit-d domname /etc/passwd -e 's/^root:.*?:/root::/'
What really happens is that the snippet is evaluated as a Perl
expression for each line of the file. The line, including the final
"\n", is passed in $_ and the expression should update $_ or leave it
unchanged.
To delete a line, set $_ to the empty string. For example, to delete
the "apache" user account from the password file you can do:
virt-edit-d mydomain /etc/passwd -e '$_ = "" if /^apache:/'
To insert a line, prepend or append it to $_. However appending lines
to the end of the file is rather difficult this way since there is no
concept of "last line of the file" - your expression just doesn't get
called again. You might want to use the first method (setting $EDITOR)
if you want to do this.
The variable $lineno contains the current line number. As is
traditional, the first line in the file is number 1.
The return value from the expression is ignored, but the expression may
call "die" in order to abort the whole program, leaving the original
file untouched.
Remember when matching the end of a line that $_ may contain the final
"\n", or (for DOS files) "\r\n", or if the file does not end with a
newline then neither of these. Thus to match or substitute some text
at the end of a line, use this regular expression:
/some text(\r?\n)?$/
Alternately, use the perl "chomp" function, being careful not to chomp
$_ itself (since that would remove all newlines from the file):
my $m = $_; chomp $m; $m =~ /some text$/
WINDOWS PATHS
"virt-edit" has a limited ability to understand Windows drive letters
and paths (eg. "E:\foo\bar.txt").
If and only if the guest is running Windows then:
· Drive letter prefixes like "C:" are resolved against the Windows
Registry to the correct filesystem.
· Any backslash ("\") characters in the path are replaced with
forward slashes so that libguestfs can process it.
· The path is resolved case insensitively to locate the file that
should be edited.
There are some known shortcomings:
· Some NTFS symbolic links may not be followed correctly.
· NTFS junction points that cross filesystems are not followed.
USING GUESTFISHguestfish(1) is a more powerful, lower level tool which you can use
when "virt-edit" doesn't work.
Using "virt-edit" is approximately equivalent to doing:
guestfish --rw -i -d domname edit /file
where "domname" is the name of the libvirt guest, and "/file" is the
full path to the file.
The command above uses libguestfs's guest inspection feature and so
does not work on guests that libguestfs cannot inspect, or on things
like arbitrary disk images that don't contain guests. To edit a file
on a disk image directly, use:
guestfish --rw -a disk.img -m /dev/sda1 edit /file
where "disk.img" is the disk image, "/dev/sda1" is the filesystem
within the disk image to edit, and "/file" is the full path to the
file.
"virt-edit" cannot create new files. Use the guestfish commands
"touch", "write" or "upload" instead:
guestfish --rw -i -d domname touch /newfile
guestfish --rw -i -d domname write /newfile "new content"
guestfish --rw -i -d domname upload localfile /newfile
CVE-2012-2690
Old versions of both virt-edit and the guestfish "edit" command created
a new file containing the changes but did not set the permissions, etc
of the new file to match the old one. The result of this was that if
you edited a security sensitive file such as "/etc/shadow" then it
would be left world-readable after the edit.
This issue was assigned CVE-2012-2690, and is fixed in libguestfs X
1.16.
For further information, see
https://bugzilla.redhat.com/show_bug.cgi?id=788642
ENVIRONMENT VARIABLES
"EDITOR"
If set, this string is used as the editor. It may contain
arguments, eg. "emacs -nw"
If not set, "vi" is used.
SHELL QUOTING
Libvirt guest names can contain arbitrary characters, some of which
have meaning to the shell such as "#" and space. You may need to quote
or escape these characters on the command line. See the shell manual
page sh(1) for details.
EXIT STATUS
This program returns 0 if successful, or non-zero if there was an
error.
SEE ALSOguestfs(3), guestfish(1), virt-cat(1), virt-copy-in(1), virt-tar-in(1),
Sys::Guestfs(3), Sys::Guestfs::Lib(3), Sys::Virt(3),
http://libguestfs.org/, perl(1), perlre(1).
AUTHOR
Richard W.M. Jones http://people.redhat.com/~rjones/
COPYRIGHT
Copyright (C) 2009-2013 Red Hat Inc.
LICENSE
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
BUGS
To get a list of bugs against libguestfs, use this link:
https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
To report a new bug against libguestfs, use this link:
https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
When reporting a bug, please supply:
· The version of libguestfs.
· Where you got libguestfs (eg. which Linux distro, compiled from
source, etc)
· Describe the bug accurately and give a way to reproduce it.
· Run libguestfs-test-tool(1) and paste the complete, unedited output
into the bug report.
libguestfs-1.20.4 2013-03-12 virt-edit(1)
