Ubuntu Manpage: virt-tail - Follow (tail) files in a virtual machine

Provided by: libguestfs-tools_1.40.2-7ubuntu5_amd64

NAME

       virt-tail - Follow (tail) files in a virtual machine

SYNOPSIS

        virt-tail [--options] -d domname file [file ...]

        virt-tail [--options] -a disk.img [-a disk.img ...] file [file ...]

DESCRIPTION

       "virt-tail" is a command line tool to follow (tail) the contents of "file" where "file"
       exists in the named virtual machine (or disk image).  It is similar to the ordinary
       command "tail -f".

       Multiple filenames can be given, in which case each is followed separately.  Each filename
       must be a full path, starting at the root directory (starting with '/').

       The command keeps running until:

       •   The user presses the ^C or an interrupt signal is received.

       •   None of the listed files was found in the guest, or they all get deleted.

       •   There is an unrecoverable error.

EXAMPLE

       Follow /var/log/messages inside a virtual machine called "mydomain":

        virt-tail -d mydomain /var/log/messages

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.

-a URI
--add URI
Add a remote disk. See "ADDING REMOTE STORAGE" in guestfish(1).

-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 (-a), 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-tail 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.

-f
--follow
This option is ignored. virt-tail always behaves like tail(1) -f. You don't need to
specify the -f option.

--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-tail --format=raw -a disk.img file

forces raw format (no auto-detection) for disk.img.

virt-tail --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).

--key SELECTOR
Specify a key for LUKS, to automatically open a LUKS device when using the inspection.
"SELECTOR" can be in one of the following formats:

--key "DEVICE":key:KEY_STRING
Use the specified "KEY_STRING" as passphrase.

--key "DEVICE":file:FILENAME
Read the passphrase from FILENAME.

--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.

-m dev[:mountpoint[:options[:fstype]]]
--mount dev[:mountpoint[:options[:fstype]]]
Mount the named partition or logical volume on the given mountpoint.

If the mountpoint is omitted, it defaults to /.

Specifying any mountpoint disables the inspection of the guest and the mount of its
root and all of its mountpoints, so make sure to mount all the mountpoints needed to
work with the filenames given as arguments.

If you don’t know what filesystems a disk image contains, you can either run guestfish
without this option, then list the partitions, filesystems and LVs available (see
"list-partitions", "list-filesystems" and "lvs" commands), or you can use the
virt-filesystems(1) program.

The third (and rarely used) part of the mount parameter is the list of mount options
used to mount the underlying filesystem. If this is not given, then the mount options
are either the empty string or "ro" (the latter if the --ro flag is used). By
specifying the mount options, you override this default choice. Probably the only
time you would use this is to enable ACLs and/or extended attributes if the filesystem
can support them:

-m /dev/sda1:/:acl,user_xattr

Using this flag is equivalent to using the "mount-options" command.

The fourth part of the parameter is the filesystem driver to use, such as "ext3" or
"ntfs". This is rarely needed, but can be useful if multiple drivers are valid for a
filesystem (eg: "ext2" and "ext3"), or if libguestfs misidentifies a filesystem.

-v
--verbose
Enable verbose messages for debugging.

-V
--version
Display version number and exit.

-x Enable tracing of libguestfs API calls.

LOG FILES

       To list out the log files from guests, see the related tool virt-log(1).  It understands
       binary log formats such as the systemd journal.

WINDOWS PATHS

       "virt-tail" 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 displayed.

       There are some known shortcomings:

       •   Some NTFS symbolic links may not be followed correctly.

       •   NTFS junction points that cross filesystems are not followed.

EXIT STATUS

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

AUTHOR

       Richard W.M. Jones http://people.redhat.com/~rjones/

COPYRIGHT

       Copyright (C) 2016 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.