guestfs-release-notes - libguestfs Release Notes


These release notes only cover the differences from the previous stable/dev branch split (1.22.0). For detailed changelogs, please see the git repository, or the ChangeLog file distributed in the tarball.

New features

User-Mode Linux (UML) can be used as an alternative backend (ie. instead of KVM). This improves performance especially when using libguestfs inside a VM (eg. in the cloud). UML is supported as a first-class backend. See "USER-MODE LINUX BACKEND" in guestfs(3) for how to use this.

ARM (32 bit) and PPC64 are now fully supported.


virt-builder(1) is a new tool for building virtual machine images. It lets you rapidly and securely create guests and customize them.

New virt-sysprep(1) operations: Remove files in /tmp and /var/tmp. Remove RPM database files. Change root and user passwords. More log files are removed. New operations which are not enabled by default: Create random UUIDs for filesystems. Reset firewall rules. (Wanlong Gao)

virt-resize(1) and virt-sysprep can now use URIs to specify a remote disk.

Use guestfish -N filename=type to create a named disk image (instead of the default test1.img etc).

virt-sparsify(1) now tests if there is enough disk space to complete the operation, instead of possibly running out of space half way through.

virt-format(1) and virt-make-fs(1): new --label option for setting filesystem label.

virt-resize --no-sparse flag can be used to resize on to partitions and other targets that are not zeroed.

Language bindings

New bindings for the Go programming language.


Support for the systemd journal.

guestfs_add_drive_opts can now control the qemu caching mode through a new cachemode parameter. You can select improved performance for temporary drives, or safety.

guestfs_set_label now works for XFS and btrfs.

New GUESTFS_EVENT_WARNING event for warning messages.


Better inspection of SUSE guests (Olaf Hering).

Better support for non-standard Windows %systemroot% (Matthew Booth).

Enhanced error reporting for Augeas errors.



A denial of service was possible when inspecting certain guests. The fix has been backported to 1.20 and 1.22 branches.


Fix insecure temporary directory handling for remote guestfish. The fix has been backported to 1.20 and 1.22 branches.

New APIs

 add-drive-scratch: Add a temporary scratch drive
 journal-open: Systemd journal support
 remount: Allow rw flag to be adjusted on mounted filesystems
 set-uuid: Set UUID of filesystem

is-file, is-dir, is-blockdev, is-chardev, is-fifo, is-socket APIs now have an extra followsymlinks flag.

add-drive has a new cachemode parameter.

Build changes

The following packages are required to build libguestfs 1.24:

Augeas ≥ 1.0.0

The following optional packages may be added to enhance functionality but are not required:


To read journal files from guests which use that.


For UML backend.


For virt-builder.

golang ≥ 1.1.1

For Go language bindings.


New make check-* rules replace make extra-tests. See make help and guestfs(3) for details.

Perl code can now be valgrinded.

Inspection code is now fuzz-tested.

make no longer recurses into the generator directory in every other directory. This reduces the overhead of builds considerably.

Additional tests for Augeas, hivex.

Add a launch timeout of 20 minutes waiting for the appliance to start up.

Add a timeout (4 hours) to all tests so we can catch the case where qemu or other components hang.

Use kvmclock and -cpu host. This improves clock stability and overall performance.

./configure --enable-packet-dump mode is fixed.

./configure --enable-valgrind-daemon mode has been rewritten. It is now feasible for developers to keep this flag enabled at all times.

Backends have been refactored to be modular (although they are not actually loadable modules).

When enabled, the network now uses resolver configuration (ie. /etc/resolv.conf) from the host.

Bugs fixed

libguestfs-tools.conf should have a man page

valgrind errors in btrfs_subvolume_list

mke2fs can't return the correct filesystem type when blockscount is less than 2048 for ext3

Update "rsync-out" helpout for using wildcard

Argument 'excludes' of tar-out does not work

virt-format uses wrong partition type for vfat filesystems

'sh' command before mount causes daemon to segfault

guestfish does not work when you mix --remote and --add options

guestfish remote prints "libguestfs: error: waitpid (qemu): No child processes"

list-filesystems command fails if there are no block devices

cache=none/O_DIRECT workaround doesn't work for images with backing files

cap-get-file will return error if the file has not be set capabilities

RFE: Implement set-uuid command

RFE: Implement set-label for xfs

Can't set acl value for a specified user with 'acl-set-file'

libguestfs double free when kernel link fails during launch

Make xfs filesystem failed with specified blocksize, gives "unknown option -b" error

"hivex-commit" should fail with a relative path

disk-format "qemu-img info: JSON parse error" when target file does not exist

mke2fs-J should give a meaningful error when specified type is anything except 'ext{2,3,4}'

Specifying virtio interface ('iface' parameter) breaks the direct backend - libguestfs hangs

"virt-resize --expand" and "virt-resize --resize" outputs error message for Win2008 32bit OS

inspection: Augeas expressions are broken with augeas >= 0.10

virt-resize --expand fails on Ubuntu Cloud Image

Regression: Fedora inspection broken by change from guestfs_exists to guestfs_is_file

txz-out command produces a bzip2-compressed file (should be xz-compressed)

upload to a directory occasionally hangs instead of failing

virt-sysprep should support URL-type arguments

blockdev-setbsz succeeds, but does not affect blockdev-getbsz


guestfs-examples(1), guestfs-faq(1), guestfs-performance(1), guestfs-recipes(1), guestfs-testing(1), guestfs(3), guestfish(1),


Richard W.M. Jones


Copyright (C) 2009-2023 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.


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