Provided by: libguestfs-tools_1.40.2-2ubuntu6_amd64 bug

NAME

       virt-rescue - Run a rescue shell on a virtual machine

SYNOPSIS

        virt-rescue [--options] -d domname

        virt-rescue [--options] -a disk.img [-a disk.img ...] [-i]

       Old style:

        virt-rescue [--options] domname

        virt-rescue [--options] disk.img [disk.img ...]

WARNING

       Using "virt-rescue" in write mode on live virtual machines, or concurrently with other
       disk editing tools, can be dangerous, potentially causing disk corruption.  The virtual
       machine must be shut down before you use this command, and disk images must not be edited
       concurrently.

       Use the --ro (read-only) option to use "virt-rescue" safely if the disk image or virtual
       machine might be live.  You may see strange or inconsistent results if running
       concurrently with other changes, but with this option you won't risk disk corruption.

DESCRIPTION

       virt-rescue is like a Rescue CD, but for virtual machines, and without the need for a CD.
       virt-rescue gives you a rescue shell and some simple recovery tools which you can use to
       examine or rescue a virtual machine or disk image.

       You can run virt-rescue on any virtual machine known to libvirt, or directly on disk
       image(s):

        virt-rescue -d GuestName -i

        virt-rescue --ro -a /path/to/disk.img -i

        virt-rescue -a /dev/sdc

       For live VMs you must use the --ro option.

       When you run virt-rescue on a virtual machine or disk image, you are placed in an
       interactive bash shell where you can use many ordinary Linux commands.  What you see in /
       (/bin, /lib etc) is the rescue appliance.  You must mount the virtual machine’s
       filesystems.  There is an empty directory called /sysroot where you can mount filesystems.

       To automatically mount the virtual machine’s filesystems under /sysroot use the -i option.
       This uses libguestfs inspection to find the filesystems and mount them in the right place.
       You can also mount filesystems individually using the -m option.

       Another way is to list the logical volumes (with lvs(8)) and partitions (with parted(8))
       and mount them by hand:

        ><rescue> lvs
        LV      VG        Attr   LSize   Origin Snap%  Move Log Copy%  Convert
        lv_root vg_f15x32 -wi-a-   8.83G
        lv_swap vg_f15x32 -wi-a- 992.00M
        ><rescue> mount /dev/vg_f15x32/lv_root /sysroot
        ><rescue> mount /dev/vda1 /sysroot/boot
        ><rescue> ls /sysroot

       Another command to list available filesystems is virt-filesystems(1).

       To run commands in a Linux guest (for example, grub), you should chroot into the /sysroot
       directory first:

        ><rescue> chroot /sysroot

   NOTES
       Virt-rescue can be used on any disk image file or device, not just a virtual machine.  For
       example you can use it on a blank file if you want to partition that file (although we
       would recommend using guestfish(1) instead as it is more suitable for this purpose).  You
       can even use virt-rescue on things like USB drives, SD cards and hard disks.

       You can get virt-rescue to give you scratch disk(s) to play with.  This is useful for
       testing out Linux utilities (see --scratch).

       Virt-rescue does not require root.  You only need to run it as root if you need root to
       open the disk image.

       This tool is just designed for quick interactive hacking on a virtual machine.  For more
       structured access to a virtual machine disk image, you should use guestfs(3).  To get a
       structured shell that you can use to make scripted changes to guests, use guestfish(1).

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).

       --append KERNELOPTS
           Pass additional options to the rescue kernel.

       -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.

       -e none
           Disable the escape key.

       -e KEY
           Set the escape key to the given key sequence.  The default is "^]".  To specify the
           escape key you can use:

           "^x"
               Control key + "x" key.

           "none"
               -e none means there is no escape key, escapes are disabled.

           See "ESCAPE KEY" below for further information.

       --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-rescue --format=raw -a disk.img

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

            virt-rescue --format=raw -a disk.img --format -a another.img

           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).

       -i
       --inspector
           Using virt-inspector(1) code, inspect the disks looking for an operating system and
           mount filesystems as they would be mounted on the real virtual machine.

           The filesystems are mounted on /sysroot in the rescue environment.

       --memsize MB
           Change the amount of memory allocated to the rescue system.  The default is set by
           libguestfs and is small but adequate for running system tools.  The occasional program
           might need more memory.  The parameter is specified in megabytes.

       -m dev[:mountpoint[:options[:fstype]]]
       --mount dev[:mountpoint[:options[:fstype]]]
           Mount the named partition or logical volume on the given mountpoint in the guest (this
           has nothing to do with mountpoints in the host).

           If the mountpoint is omitted, it defaults to /.  You have to mount something on /.

           The filesystems are mounted under /sysroot in the rescue environment.

           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

           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.

       --network
           Enable QEMU user networking in the guest.  See "NETWORK".

       -r
       --ro
           Open the image read-only.

           The option must always be used if the disk image or virtual machine might be running,
           and is generally recommended in cases where you don't need write access to the disk.

           See also "OPENING DISKS FOR READ AND WRITE" in guestfish(1).

       --scratch
       --scratch=N
           The --scratch option adds a large scratch disk to the rescue appliance.  --scratch=N
           adds "N" scratch disks.  The scratch disk(s) are deleted automatically when virt-
           rescue exits.

           You can also mix -a, -d and --scratch options.  The scratch disk(s) are added to the
           appliance in the order they appear on the command line.

       --selinux
           This option is provided for backwards compatibility and does nothing.

       --smp N
           Enable N ≥ 2 virtual CPUs in the rescue appliance.

       --suggest
           This option was used in older versions of virt-rescue to suggest what commands you
           could use to mount filesystems under /sysroot.  For the current version of virt-
           rescue, it is easier to use the -i option instead.

           This option implies --ro and is safe to use even if the guest is up or if another
           virt-rescue is running.

       -v
       --verbose
           Enable verbose messages for debugging.

       -V
       --version
           Display version number and exit.

       -w
       --rw
           This changes the -a, -d and -m options so that disks are added and mounts are done
           read-write.

           See "OPENING DISKS FOR READ AND WRITE" in guestfish(1).

       -x  Enable tracing of libguestfs API calls.

OLD-STYLE COMMAND LINE ARGUMENTS

       Previous versions of virt-rescue allowed you to write either:

        virt-rescue disk.img [disk.img ...]

       or

        virt-rescue guestname

       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.

NETWORK

       Adding the --network option enables QEMU user networking in the rescue appliance.  There
       are some differences between user networking and ordinary networking:

       ping does not work
           Because the ICMP ECHO_REQUEST protocol generally requires root in order to send the
           ping packets, and because virt-rescue must be able to run as non-root, QEMU user
           networking is not able to emulate the ping(8) command.  The ping command will appear
           to resolve addresses but will not be able to send or receive any packets.  This does
           not mean that the network is not working.

       cannot receive connections
           QEMU user networking cannot receive incoming connections.

       making TCP connections
           The virt-rescue appliance needs to be small and so does not include many network
           tools.  In particular there is no telnet(1) command.  You can make TCP connections
           from the shell using the magical /dev/tcp/<hostname>/<port> syntax:

            exec 3<>/dev/tcp/redhat.com/80
            echo "GET /" >&3
            cat <&3

           See bash(1) for more details.

ESCAPE KEY

       Virt-rescue supports various keyboard escape sequences which are entered by pressing "^]"
       (Control key + "]" key).

       You can change the escape key using the -e option on the command line (see above), and you
       can disable escapes completely using -e none.  The rest of this section assumes the
       default escape key.

       The following escapes can be used:

       "^] ?"
       "^] h"
           Prints a brief help text about escape sequences.

       "^] i"
           Prints brief libguestfs inspection information for the guest.  This only works if you
           used -i on the virt-rescue command line.

       "^] q"
       "^] x"
           Quits virt-rescue immediately.

       "^] s"
           Synchronize the filesystems (sync).

       "^] u"
           Unmounts all the filesystems, except for the root (appliance) filesystems.

       "^] z"
           Suspend virt-rescue (like pressing "^Z" except that it affects virt-rescue rather than
           the program inside the rescue shell).

       "^] ^]"
           Sends the literal character "^]" (ASCII 0x1d) through to the rescue shell.

CAPTURING CORE DUMPS

       If you are testing a tool inside virt-rescue and the tool (not virt-rescue) segfaults, it
       can be tricky to capture the core dump outside virt-rescue for later analysis.  This
       section describes one way to do this.

       1.  Create a scratch disk for core dumps:

            truncate -s 4G /tmp/corefiles
            virt-format --partition=mbr --filesystem=ext2 -a /tmp/corefiles
            virt-filesystems -a /tmp/corefiles --all --long -h

       2.  When starting virt-rescue, attach the core files disk last:

            virt-rescue --rw [-a ...] -a /tmp/corefiles

           NB. If you use the --ro option, then virt-rescue will silently not write any core
           files to /tmp/corefiles.

       3.  Inside virt-rescue, mount the core files disk.  Note replace /dev/sdb1 with the last
           disk index.  For example if the core files disk is the last of four disks, you would
           use /dev/sdd1.

            ><rescue> mkdir /tmp/mnt
            ><rescue> mount /dev/sdb1 /tmp/mnt

       4.  Enable core dumps in the rescue kernel:

            ><rescue> echo '/tmp/mnt/core.%p' > /proc/sys/kernel/core_pattern
            ><rescue> ulimit -Hc unlimited
            ><rescue> ulimit -Sc unlimited

       5.  Run the tool that caused the core dump.  The core dump will be written to
           /tmp/mnt/core.PID.

            ><rescue> ls -l /tmp/mnt
            total 1628
            -rw------- 1 root root 1941504 Dec  7 13:13 core.130
            drwx------ 2 root root   16384 Dec  7 13:00 lost+found

       6.  Before exiting virt-rescue, unmount (or at least sync) the disks:

            ><rescue> umount /tmp/mnt
            ><rescue> exit

       7.  Outside virt-rescue, the core dump(s) can be removed from the disk using guestfish(1).
           For example:

            guestfish --ro -a /tmp/corefiles -m /dev/sda1
            ><fs> ll /
            ><fs> download /core.NNN /tmp/core.NNN

ENVIRONMENT VARIABLES

       Several environment variables affect virt-rescue.  See "ENVIRONMENT VARIABLES" in
       guestfs(3) for the complete list.

FILES

       $XDG_CONFIG_HOME/libguestfs/libguestfs-tools.conf
       $HOME/.libguestfs-tools.rc
       $XDG_CONFIG_DIRS/libguestfs/libguestfs-tools.conf
       /etc/libguestfs-tools.conf
           This configuration file controls the default read-only or read-write mode (--ro or
           --rw).

           See libguestfs-tools.conf(5).

SEE ALSO

       guestfs(3), guestfish(1), virt-cat(1), virt-edit(1), virt-filesystems(1),
       libguestfs-tools.conf(5), http://libguestfs.org/.

AUTHOR

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

COPYRIGHT

       Copyright (C) 2009-2019 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.