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NAME

virt-get-kernel - Extract kernel and ramdisk from guests

SYNOPSIS

virt-get-kernel [--options] -d domname
virt-get-kernel [--options] -a disk.img

DESCRIPTION

This program extracts the kernel and initramfs from a guest.

The format of the disk image is automatically detected unless you specify it by using the --format option.

In the case where the guest contains multiple kernels, the one with the highest version number is chosen. To extract arbitrary kernels from the disk image, see guestfish(1). To extract the entire "/boot" directory of a guest, see virt-copy-out(1).

OPTIONS

--help

Display help.

-a file
--add file

Add file which should be a disk image from a virtual machine.

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. The URI format is compatible with guestfish. See "ADDING REMOTE STORAGE" in guestfish(1).

--blocksize 512
--blocksize 4096

This parameter sets the sector size of the disk image added with -a option and is ignored for libvirt guest added with -d option. See also "guestfs_add_drive_opts" in guestfs(3).

--colors
--colours

Use ANSI colour sequences to colourize messages. This is the default when the output is a tty. If the output of the program is redirected to a file, ANSI colour sequences are disabled unless you use this option.

-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-get-kernel 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.

--format raw|qcow2|..
--format auto

The default for the -a option is to auto-detect the format of the disk image. Using this forces the disk format for the -a option on the command line.

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.
--key NAME:key:KEY_STRING
--key UUID:key:KEY_STRING
--key all:key:KEY_STRING

"NAME" is the libguestfs device name (eg. "/dev/sda1"). "UUID" is the device UUID. "all" means try the key against any encrypted device.

Use the specified "KEY_STRING" as passphrase.

--key NAME:file:FILENAME
--key UUID:file:FILENAME
--key all:file:FILENAME

Read the passphrase from FILENAME.

--key NAME:clevis
--key UUID:clevis
--key all:clevis

Attempt passphrase-less unlocking for the device with Clevis, over the network. Please refer to "ENCRYPTED DISKS" in guestfs(3) for more information on network-bound disk encryption (NBDE).

Note that if any such option is present on the command line, QEMU user networking will be automatically enabled for the libguestfs appliance.

--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.

If there are multiple encrypted devices then you may need to supply multiple keys on stdin, one per line.

--machine-readable
--machine-readable=format

This option is used to make the output more machine friendly when being parsed by other programs. See "MACHINE READABLE OUTPUT" below.

-o directory
--output directory

This option specifies the output directory where kernel and initramfs from the guest are written.

If not specified, the default output is the current directory.

--prefix prefix

This option specifies a prefix for the extracted files.

If a prefix is specified, then there will be a dash ("-") after the prefix and before the rest of the file name; for example, a kernel in the guest like "vmlinuz-3.19.0-20-generic" is saved as "mydistro-vmlinuz-3.19.0-20-generic" when the prefix is "mydistro".

See also --unversioned-names.

--quiet

Don’t print ordinary progress messages.

--unversioned-names

This option affects the destination file name of extracted files.

If enabled, files will be saved locally just with the base name; for example, kernel and ramdisk in the guest like "vmlinuz-3.19.0-20-generic" and "initrd.img-3.19.0-20-generic" are saved respectively as "vmlinuz" and "initrd.img".

See also --prefix.

--verbose

Enable verbose messages for debugging.

--version

Display version number and exit.

--wrap

Wrap error, warning, and informative messages. This is the default when the output is a tty. If the output of the program is redirected to a file, wrapping is disabled unless you use this option.

MACHINE READABLE OUTPUT

The --machine-readable option can be used to make the output more machine friendly, which is useful when calling virt-get-kernel from other programs, GUIs etc.

Use the option on its own to query the capabilities of the virt-get-kernel binary. Typical output looks like this:

$ virt-get-kernel --machine-readable
virt-get-kernel

A list of features is printed, one per line, and the program exits with status 0.

It is possible to specify a format string for controlling the output; see "ADVANCED MACHINE READABLE OUTPUT" in guestfs(3).

ENVIRONMENT VARIABLES

For other environment variables which affect all libguestfs programs, see "ENVIRONMENT VARIABLES" in guestfs(3).

EXIT STATUS

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

SEE ALSO

guestfs(3), guestfish(1), guestmount(1), virt-copy-out(1), virt-drivers(1), http://libguestfs.org/.

AUTHOR

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

COPYRIGHT

Copyright (C) 2013-2023 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: