Provided by: libguestfs-tools_1.32.2-4ubuntu2.2_amd64 
NAME
virt-dib - Run diskimage-builder elements
SYNOPSIS
virt-dib -B DIB-LIB [options] elements...
DESCRIPTION
Virt-dib is a tool for using the elements of "diskimage-builder" to build a new disk image, generate new
ramdisks, etc.
Virt-dib is intended as safe replacement for "diskimage-builder" and its "ramdisk-image-create" mode, see
"COMPARISON WITH DISKIMAGE-BUILDER" for a quick comparison with usage of "diskimage-builder".
"diskimage-builder" is part of the TripleO OpenStack project: https://wiki.openstack.org/wiki/TripleO.
EXAMPLES
Build simple images of distributions
virt-dib \
-B /path/to/diskimage-builder/lib \
-p /path/to/diskimage-builder/elements \
--envvar DIB_RELEASE=jessie \
--name debian-jessie \
debian vm
This builds a Debian Jessie (8.x) disk image, suitable for running as virtual machine, saved as
debian-jessie.qcow2.
Build ramdisks
virt-dib \
-B /path/to/diskimage-builder/lib \
-p /path/to/diskimage-builder/elements \
--ramdisk \
--name ramdisk \
ubuntu deploy-ironic
This builds a ramdisk for the Ironic OpenStack component based on the Ubuntu distribution.
OPTIONS
--help
Display help.
-B PATH
Set the path to the library directory of "diskimage-builder". This is usually the lib subdirectory in
the sources and when installed, and /usr/share/diskimage-builder/lib when installed in /usr.
This parameter is mandatory, as virt-dib needs to provide it for the elements (as some of them might
use scripts in it). Virt-dib itself does not make use of the library directory.
--arch ARCHITECTURE
Use the specified architecture for the output image. The default value is the same as the host
running virt-dib.
Right now this option does nothing more than setting the "ARCH" environment variable for the
elements, and it's up to them to produce an image for the requested architecture.
--debug LEVEL
Set the debug level to "LEVEL", which is a non-negative integer number. The default is 0.
This debug level is different than what -x and -v set, and it increases the debugging information
printed out. Specifically, this sets the "DIB_DEBUG_TRACE", and any value > 0 enables tracing in the
scripts executed.
--drive DISK
Add the specified disk to be used as helper drive where to cache files of the elements, like disk
images, distribution packages, etc.
See "HELPER DRIVE".
-p PATH
--element-path PATH
Add a new path with elements. Paths are used in the same order as the -p parameters appear, so a
path specified first is looked first, and so on.
Obviously, it is recommended to add the path to the own elements of "diskimage-builder", as most of
the other elements will rely on them.
--extra-packages PACKAGE,...
Install additional packages in the image being built.
This relies on the "install-packages" binary provided by the package management elements.
This option can be specified multiple times, each time with multiple packages separated by comma.
--envvar VARIABLE
--envvar VARIABLE=VALUE
Carry or set an environment variable for the elements.
See "ENVIRONMENT VARIABLES" below for more information on the interaction and usage of environment
variables.
This option can be used in two ways:
--envvar VARIABLE
Carry the environment variable "VARIABLE". If it is not set, nothing is exported to the elements.
--envvar VARIABLE=VALUE
Set the environment variable "VARIABLE" with value "VALUE" for the elements, regardless whether
an environment variable with the same name exists.
This can be useful to pass environment variable without exporting them in the environment where
virt-dib runs.
--exclude-element ELEMENT
Ignore the specified element.
--exclude-script SCRIPT
Ignore any element script named "SCRIPT", whichever element it is in.
This can be useful in case some script does not run well with virt-dib, for example when they really
need "diskimage-builder"'s environment.
--formats FORMAT,...
Set the list of output formats, separating them with comma.
Supported formats are:
"qcow2" (enabled by default)
QEMU's qcow2.
"raw"
Raw disk format.
"tar"
An uncompressed tarball.
"vhd"
"Virtual Hard Disk" disk image. This output format requires the "vhd-util" tool.
Please note that the version of "vhd-util" tool needs to be patched to support the "convert"
subcommand, and to be bootable. The patch is available here:
https://github.com/emonty/vhd-util/blob/master/debian/patches/citrix.
--fs-type FILESYSTEM
Set the filesystem type to use for the root filesystem. The default is "ext4".
See also "guestfs_filesystem_available" in guestfs(3).
--image-cache DIRECTORY
Set the path in the host where cache the resources used by the elements of the "extra-data.d" phase.
The default is ~/.cache/image-create.
Please note that most of the resources fetched after "extra-data" will be cached in the helper drive
specified with --drive; see also "HELPER DRIVE".
--install-type TYPE
Specify the default installation type. Defaults to "source".
Set to "package" to use package based installations by default.
--machine-readable
This option is used to make the output more machine friendly when being parsed by other programs.
See "MACHINE READABLE OUTPUT" below.
-m MB
--memsize MB
Change the amount of memory allocated to the appliance. Increase this if you find that the virt-dib
execution runs out of memory.
The default can be found with this command:
guestfish get-memsize
--mkfs-options "OPTION STRING"
Add the specified options to mkfs(1), to be able to fine-tune the root filesystem creation. Note
that this is not possible to override the filesystem type.
You should use --mkfs-options at most once. To pass multiple options, separate them with space, eg:
virt-dib ... --mkfs-options '-O someopt -I foo'
--network
--no-network
Enable or disable network access from the guest during the installation.
Enabled is the default. Use --no-network to disable access.
The network only allows outgoing connections and has other minor limitations. See "NETWORK" in
virt-rescue(1).
This does not affect whether the guest can access the network once it has been booted, because that
is controlled by your hypervisor or cloud environment and has nothing to do with virt-dib.
If you use --no-network, then the environment variable "DIB_OFFLINE" is set to 1, signaling the
elements that they should use only cached resources when available. Note also that, unlike with
"diskimage-builder" where elements may still be able to access to the network even with
"DIB_OFFLINE=", under virt-dib network will be fully unaccessible.
--name NAME
Set the name of the output image file. The default is "image".
According to the chosen name, there will be the following in the current directory:
$NAME.ext
For each output format, a disk image named after the outout image with the extension depending on
the format; for example: $NAME.qcow2, $NAME.raw, etc.
Not applicable in ramdisk mode, see "RAMDISK BUILDING".
$NAME.d
A directory containing any files created by the elements, for example dib-manifests directory
(created by the "manifests" element), ramdisks and kernels in ramdisk mode, and so on.
--no-delete-on-failure
Don't delete the output files on failure to build. You can use this to debug failures to run
scripts.
The default is to delete the output file if virt-dib fails (or, for example, some script that it runs
fails).
-q
--quiet
Don't print ordinary progress messages.
--qemu-img-options option[,option,...]
Pass --qemu-img-options option(s) to the qemu-img(1) command to fine-tune the output format. Options
available depend on the output format (see --formats) and the installed version of the qemu-img
program.
You should use --qemu-img-options at most once. To pass multiple options, separate them with commas,
eg:
virt-dib ... --qemu-img-options cluster_size=512,preallocation=metadata ...
--ramdisk
Set the ramdisk building mode.
See "RAMDISK BUILDING".
--ramdisk-element NAME
Set the name for the additional element added in ramdisk building mode. The default is "ramdisk".
See "RAMDISK BUILDING".
--root-label LABEL
Set the label for the root filesystem in the created image.
Please note that some filesystems have different restrictions on the length of their labels; for
example, on "ext2/3/4" filesystems labels cannot be longer than 16 characters, while on "xfs" they
have at most 12 characters.
The default depends on the actual filesystem for the root partition (see --fs-type): on "xfs" is
"img-rootfs", while "cloudimg-rootfs" on any other filesystem.
--size SIZE
Select the size of the output disk, where the size can be specified using common names such as "32G"
(32 gigabytes) etc. The default size is "5G".
To specify size in bytes, the number must be followed by the lowercase letter b, eg:
"--size 10737418240b".
See also virt-resize(1) for resizing partitions of an existing disk image.
--skip-base
Skip the inclusion of the "base" element.
--smp N
Enable N ≥ 2 virtual CPUs for scripts to use.
-u Do not compress resulting qcow2 images. The default is to compress them.
-v
--verbose
Enable debugging messages.
-V
--version
Display version number and exit.
-x Enable tracing of libguestfs API calls.
ENVIRONMENT VARIABLES
Unlike with "diskimage-builder", the environment of the host is not inherited in the appliance when
running most of the elements (i.e. all the ones different than "extra-data.d").
To set environment for the elements being run, it is necessary to tell virt-dib to use them, with the
option --envvar. Such option allows to selectively export environment variables when running the
elements, and it is the preferred way to pass environment variables to the elements.
To recap: if you want the environment variable "MYVAR" (and its content) to be available to the elements,
you can do either
export MYVAR # whichever is its value
virt-dib ... --envvar MYVAR ...
or
virt-dib ... --envvar MYVAR=value_of_it ...
HELPER DRIVE
Virt-dib runs most of the element in its own appliance, and thus not on the host. Because of this, there
is no possibility for elements to cache resources directly on the host.
To solve this issue, virt-dib allows the usage of an helper drive where to store cached resources, like
disk images, distribution packages, etc. While this means that there is a smaller space available for
caching, at least it allows to limit the space on the host for caches, without assuming that elements
will do that by themselves.
Currently this disk is either required to have a single partition on it, or the first partition on it
will be used. A disk with the latter configuration can be easily created with guestfish(1) like the
following:
guestfish -N filename.img=fs:ext4:10G
The above will create a disk image called filename.img, 10G big, with a single partition of type ext4;
see "PREPARED DISK IMAGES" in guestfish(1).
It is recommended for it to be ≥ 10G or even more, as elements will cache disk images, distribution
packages, etc. As with any disk image, the helper disk can be easily resized using virt-resize(1) if
more space in it is needed.
The drive can be accessed like any other disk image, for example using other tools of libguestfs such as
guestfish(1):
guestfish -a filename.img -m /dev/sda1
If no helper drive is specified with --drive, all the resources cached during a virt-dib run will be
discarded.
RESOURCES INSIDE THE DRIVE
Inside the helper drive, it is possible to find the following resources:
/home
This directory is set as "HOME" environment variable during the build. It contains mostly the image
cache (saved as /home/.cache/image-create), and whichever other resource is cached in the home
directory of the user running the various tools.
/virt-dib-*.log
These are the logs of the elements being run within the libguestfs appliance, which means all the
hooks except "extra-data.d".
RAMDISK BUILDING
Virt-dib can emulate also "ramdisk-image-create", which is a secondary operation mode of
"diskimage-builder". Instead of being a different tool name, virt-dib provides easy access to this mode
using the --ramdisk switch.
In this mode:
• there is an additional ramdisk element added (see --ramdisk-element)
• no image is produced (so --formats is ignored)
• $NAME.d (see --name) will contain initrd, kernel, etc
TEMPORARY DIRECTORY
Virt-dib uses the standard temporary directory used by libguestfs, see "ENVIRONMENT VARIABLES" in
guestfs(3).
By default this location is /tmp (default value for "TMPDIR"), which on some systems may be on a tmpfs
filesystem, and thus defaulting to a maximum size of half of physical RAM. If virt-dib exceeds this, it
may hang or exit early with an error. The solution is to point "TMPDIR" to a permanent location used as
temporary location, for example:
mkdir local-tmp
env TMPDIR=$PWD/local-tmp virt-dib ...
rm -rf local-tmp
EXTRA DEPENDENCIES
Because of virt-dib runs most of the elements in its own appliance, all the tools and libraries used by
elements running outside the guest (typically "root.d", "block-device.d", and "cleanup.d") need to be
present in the appliance as well. In case they are not, scripts will fail mostly with a "command not
found" error.
For tools and libraries packaged by the distribution, the easy solution is to tell libguestfs to include
additional packages in the appliance. This is doable by e.g. creating a new file with the additional
packages:
# echo wget > /usr/lib64/guestfs/supermin.d/dib-my-extra
The actual path to the supermin.d directory depends on the distribution; additional files can list more
packages, each in its own line.
COMPARISON WITH DISKIMAGE-BUILDER
Virt-dib is intended as safe replacement for "diskimage-builder" and its "ramdisk-image-create" mode; the
user-notable differences consist in:
• the command line arguments; some of the arguments are the same as available in "diskimage-builder",
while some have different names:
disk-image-create virt-dib
----------------- --------
-a ARCH --arch ARCH
--image-size SIZE --size SIZE
--max-online-resize SIZE doable using --mkfs-options
-n --skip-base
-o IMAGENAME --name IMAGENAME
-p PACKAGE(S) --extra-packages PACKAGE(S)
-t FORMAT(S) --formats FORMAT(S)
-x --debug N
• the location of non-image output files (like ramdisks and kernels)
• the way some of the cached resources are saved: using an helper drive, not directly on the disk where
virt-dib is run
• the need to specify a target size for the output disk, as opposed to "diskimage-builder" calculating
an optimal one
• the handling of environment variables, see "ENVIRONMENT VARIABLES".
Furthermore, other than the libguestfs own environment variables (see "ENVIRONMENT VARIABLES" in
guestfs(3)), virt-dib does not read any other environment variable: this means that all the options
and behaviour changes are specified solely using command line arguments
• "extra-data.d" scripts run in the host environment, before all the other ones (even "root.d"); this
means that, depending on the configuration for the elements, some of them may fail due to missing
content (usually directories) in "TMP_HOOKS_PATH".
Workarounds for this may be either:
• fix the "extra-data.d" scripts to create the missing directories
• create (and use) a simple element with a "extra-data.d" script named e.g. 00-create-missing-dirs
to create the missing directories
• extra tools needed on some out-of-chroot phases need to be available in the appliance, see "EXTRA
DEPENDENCIES".
Elements themselves should notice no difference in they way they are run; behaviour differences may due
to wrong assumptions in elements, or not correct virt-dib emulation.
Known issues at the moment:
• (none)
MACHINE READABLE OUTPUT
The --machine-readable option can be used to make the output more machine friendly, which is useful when
calling virt-dib from other programs, GUIs etc.
Use the option on its own to query the capabilities of the virt-dib binary. Typical output looks like
this:
$ virt-dib --machine-readable
virt-dib
output:qcow2
output:tar
output:raw
output:vhd
A list of features is printed, one per line, and the program exits with status 0.
TESTING
Virt-dib has been tested with "diskimage-builder" (and its elements) ≥ 0.1.43; from time to time also
with "tripleo-image-elements" and "sahara-image-elements".
Previous versions may work, but it is not guaranteed.
EXIT STATUS
This program returns 0 if successful, or non-zero if there was an error.
SEE ALSO
guestfs(3), guestfish(1), virt-resize(1), http://libguestfs.org/.
AUTHOR
Pino Toscano ("ptoscano at redhat dot com")
COPYRIGHT
Copyright (C) 2015 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-1.32.2 2016-01-29 virt-dib(1)