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.

libguestfs-1.40.2                                  2019-02-07                                       virt-tail(1)