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rescue(8) [freebsd man page]

RESCUE(8)						    BSD System Manager's Manual 						 RESCUE(8)

NAME
rescue -- rescue utilities in /rescue DESCRIPTION
The /rescue directory contains a collection of common utilities intended for use in recovering a badly damaged system. With the transition to a dynamically-linked root beginning with FreeBSD 5.2, there is a real possibility that the standard tools in /bin and /sbin may become non-functional due to a failed upgrade or a disk error. The tools in /rescue are statically linked and should therefore be more resistant to damage. However, being statically linked, the tools in /rescue are also less functional than the standard utilities. In particular, they do not have full use of the locale, pam(3), and nsswitch libraries. If your system fails to boot, and it shows a prompt similar to: Enter full pathname of shell or RETURN for /bin/sh: the first thing to try running is the standard shell, /bin/sh. If that fails, try running /rescue/sh, which is the rescue shell. To repair the system, the root partition must first be remounted read-write. This can be done with the following mount(8) command: /rescue/mount -uw / The next step is to double-check the contents of /bin, /sbin, and /usr/lib, possibly mounting a FreeBSD rescue or ``live file system'' CD-ROM (e.g., disc2 of the officially released FreeBSD ISO images) and copying files from there. Once it is possible to successfully run /bin/sh, /bin/ls, and other standard utilities, try rebooting back into the standard system. The /rescue tools are compiled using crunchgen(1), which makes them considerably more compact than the standard utilities. To build a FreeBSD system where space is critical, /rescue can be used as a replacement for the standard /bin and /sbin directories; simply change /bin and /sbin to be symbolic links pointing to /rescue. Since /rescue is statically linked, it should also be possible to dispense with much of /usr/lib in such an environment. In contrast to its predecessor /stand, /rescue is updated during normal FreeBSD source and binary upgrades. FILES
/rescue Root of the rescue hierarchy. SEE ALSO
crunchgen(1), crash(8) HISTORY
The rescue utilities first appeared in FreeBSD 5.2. AUTHORS
The rescue system was written by Tim Kientzle <kientzle@FreeBSD.org>, based on ideas taken from NetBSD. This manual page was written by Simon L. Nielsen <simon@FreeBSD.org>, based on text by Tim Kientzle <kientzle@FreeBSD.org>. BUGS
Most of the rescue tools work even in a fairly crippled system. The most egregious exception is the rescue version of vi(1), which currently requires that /usr be mounted so that it can access the termcap(5) files. Hopefully, a failsafe termcap(3) entry will eventually be added into the ncurses(3) library, so that /rescue/vi can be used even in a system where /usr cannot immediately be mounted. In the meantime, the rescue version of the ed(1) editor can be used from /rescue/ed if you need to edit files, but cannot mount /usr. BSD
July 23, 2003 BSD

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virt-rescue(1)						      Virtualization Support						    virt-rescue(1)

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 ...] virt-rescue --suggest (-d domname | -a disk.img ...) Old style: virt-rescue [--options] domname virt-rescue [--options] disk.img [disk.img ...] WARNING
You must not use "virt-rescue" on live virtual machines. Doing so will probably result in disk corruption in the VM. "virt-rescue" tries to stop you from doing this, but doesn't catch all cases. However if you use the --ro (read only) option, then you can attach a shell to a live virtual machine. The results might be strange or inconsistent at times but you won't get 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 virt-rescue --ro -a /path/to/disk.img 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 by hand. There is an empty directory called "/sysroot" where you can mount filesystems. You can get virt-rescue to suggest mount commands for you by using the --suggest option (in another terminal): $ virt-rescue --suggest -d Fedora15 Inspecting the virtual machine or disk image ... This disk contains one or more operating systems. You can use these mount commands in virt-rescue (at the ><rescue> prompt) to mount the filesystems. # /dev/vg_f15x32/lv_root is the root of a linux operating system # type: linux, distro: fedora, version: 15.0 # Fedora release 15 (Lovelock) mount /dev/vg_f15x32/lv_root /sysroot/ mount /dev/vda1 /sysroot/boot mount --bind /dev /sysroot/dev mount --bind /dev/pts /sysroot/dev/pts mount --bind /proc /sysroot/proc mount --bind /sys /sysroot/sys 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 SD cards. 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. --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. --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). -m MB --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. --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 Enable SELinux in the rescue appliance. You should read "SELINUX" in guestfs(3) before using this option. --smp N Enable N >= 2 virtual CPUs in the rescue appliance. --suggest Inspect the disk image and suggest what mount commands should be used to mount the disks. You should use the --suggest option in a second terminal, then paste the commands into another virt-rescue. 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 and -d 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. ENVIRONMENT VARIABLES
Several environment variables affect virt-rescue. See "ENVIRONMENT VARIABLES" in guestfs(3) for the complete list. 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. FILES
$HOME/.libguestfs-tools.rc /etc/libguestfs-tools.conf This configuration file controls the default read-only or read-write mode (--ro or --rw). See "OPENING DISKS FOR READ AND WRITE" in guestfish(1). SEE ALSO
guestfs(3), guestfish(1), virt-cat(1), virt-edit(1), virt-filesystems(1), <http://libguestfs.org/>. AUTHOR
Richard W.M. Jones <http://people.redhat.com/~rjones/> COPYRIGHT
Copyright (C) 2009-2012 Red Hat Inc. 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. libguestfs-1.18.1 2013-12-07 virt-rescue(1)
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