multistrap - multiple repository bootstraps
multistrap [-a ARCH] [-d DIR] -f CONFIG_FILE
multistrap [--simulate] -f CONFIG_FILE
-?|-h|--help|--version - output the help text and exit successfully.
--dry-run - collate all the configuration settings and output a bare summary.
--simulate - same as --dry-run
(The following options can also be set in the configuration file.)
-a|--arch - architecture of the packages to put into the multistrap.
-d|--dir - directory into which the bootstrap will be installed.
-f|--file - configuration file for multistrap [required]
-s|--shortcut - shortened version of -f for files in known locations.
--tidy-up - remove apt cache data, downloaded Packages files and the apt package
cache. Same as cleanup=true.
--no-auth - allow the use of unauthenticated repositories. Same as noauth=true
--source-dir DIR - move the contents of var/cache/apt/archives/ from inside the
chroot to the specified external directory, then add the Debian source
packages for each used binary. Same as retainsources=DIR If the specified
directory does not exist, nothing is done. Requires --tidy-up in order to
calculate the full list of source packages, including dependencies.
multistrap provides a debootstrap-like method based on apt and extended to
provide support for multiple repositories, using a configuration file to
specify the relevant suites, architecture, extra packages and the mirror to
use for each bootstrap.
The aim is to create a complete bootstrap / root filesystem with all packages
installed and configured, instead of just the base system.
In most cases, users will need to create a configuration file for each different
# same as --tidy-up option if set to true
# same as --no-auth option if set to true
# keyring packages listed in each bootstrap will
# still be installed.
# extract all downloaded archives (default is true)
# whether to add the /suite to be explicit about where apt
# needs to look for packages. Default is false.
# enable MultiArch for the specified architectures
# default is empty
# aptsources is a list of sections to be used
# the /etc/apt/sources.list.d/multistrap.sources.list
# of the target. Order is not important
# the bootstrap option determines which repository
# is used to calculate the list of Priority: required packages
# and which packages go into the rootfs.
# The order of sections is not important.
This will result in a completely normal bootstrap of Debian lenny from the
specified mirror, for armel in '/opt/multistrap/'. (This configuration is
retained in the package as /usr/share/multistrap/lenny.conf
Specify a package to extend the multistrap to include that package and all
dependencies of that package.
Specify more repositories for the bootstrap by adding new sections. Section
names need to be listed in the bootstrap general option for the packages to be
included in the bootstrap.
Specify which repositories will be available to the final system at boot by
listing the section names in the aptsources general option, e.g. to exclude
some internal sources or when using a local mirror when building the rootfs.
Section names are case-insensitive.
All dependencies are resolved only by apt, using all bootstrap repositories, to
use only the most recent and most suitable dependencies. Note that multistrap
turns off Install-Recommends so if the multistrap needs a package that is only
a Recommended dependency, the recommended package needs to be specified in the
packages line explicitly. See "Explicit suite specification" for
more information on getting specific packages from specific suites.
'Architecture' and 'directory' can be overridden on the command line. Some other
general options also have command line options.
Online examples and documentation¶
"multistrap" supports a range of permutations, see the wiki and the
emdebian website for more information and example configurations:
"multistrap" includes an example configuration file with a full list
of all supported config file options:
In a similar manner to "debootstrap", "multistrap" supports
referring to configuration files in known locations by shortcuts. When using
the "--shortcut" option, "multistrap" will look for files
and then /etc/multistrap.d/
a '.conf' suffix to the specified shortcut.
These two commands are equivalent:
$ sudo multistrap -s sid
$ sudo multistrap -f /usr/share/multistrap/sid.conf
Note that "multistrap" will still fail if the configuration file
itself does not set the directory or the architecture.
"aptsources" lists the sections which should be used to create the
apt sources in the final
system. Not all "aptsources" have to appear in the
"bootstrap" section if you have some internal or local sources which
are not accessible to the installed root filesystem.
"bootstrap" lists the sections which will be used to create the
multistrap itself. Only packages listed in "bootstrap" will be
downloaded and unpacked by multistrap.
Make sure "bootstrap" lists all sections you need for apt to be able
to find all the packages to be unpacked for the multistrap.
(Older versions of multistrap supported the same option under the
"debootstrap" name - this spelling is still supported but new
configuration files should be "bootstrap" instead.
'arch' can be overridden on the command line using the "--arch"
'directory' specifies the top level directory where the bootstrap will be
created - it is not packed into a .tgz once complete.
'bootstrap' lists the Sections which will be used to specify the packages which
will be downloaded (and optionally unpacked) into the bootstrap.
'aptsources' lists the Sections which will be used to specify the apt sources in
the final system, e.g. if you need to use a local repository to generate the
rootfs which will not be available to the device at runtime, list that section
in "bootstrap" but not in "aptsources".
If you want a package to be in the rootfs, it must
be specified in the
"bootstrap" list under General.
The order of section names in either list is not important.
If "markauto" is set to true, "multistrap" will request apt
to mark all packages specified in the combined "packages" list as
manually installed and all dependencies not explicitly listed as automatically
installed in the APT extended state database. "markauto" can be used
independently of "unpack".
As with debootstrap, multistrap will continue after errors, as long as the
configuration file can be correctly parsed.
multistrap also implements the machine:variant support originally used in
Emdebian Crush, although in a different implementation. Using the cascading
configuration support, particular machine:variant combinations can be
supported by simple changes on the command line.
Setting "tarballname" to true also packs up the final filesystem into
Note that multistrap ignores any unrecognised options in the config file - this
allows for backwards-compatible behaviour as well as overloading the
multistrap config files to support other tools (like pbuilder). Use the
"--simulate" option to see the combined configuration settings.
However, if the config file itself cannot be parsed, multistrap will abort.
Check that the config file has a key and a value for each line, other than
comments. Values must all on the same line as the key.
The section name (in  brackets) needs to be unique for this configuration file
and any configuration files which this file includes. Section names are case
insensitive (all comparisons happen after conversion to lower case).
'packages' is the list of packages to be added when this Section is listed in
"bootstrap" - all package names must be listed on a single line or
the file will fail to parse. One alternative is to define your list of
packages as multiple groups with packages separated on a functional /
dependency basis, e.g. base, Xorg, networking etc. and list each group under
packages=netbase ifupdown iproute net-tools samba
As a special case, "multistrap" also supports multiple packages keys
per section, one line for each. Other keys cannot be repeated in this manner.
packages=udev mtd-utils netbase ifupdown iproute
packages=busybox net-tools samba
'source' is the apt source to use for this Section. To use a local source on the
same machine, ensure you use "copy://"
that apt is told to copy the packages into the rootfs instead of assuming it
can try to download them later - because that "later" will never
'keyring' lists the package which contains the key used by the source listed in
this Section. If no keyring is specified, the "noauth" option must
be set to true
. See Secure Apt.
'suite' is the suite to use from this source. Note that this should be the
suite, not the codename.
Suites change from time to time: (oldstable, stable, testing, sid) The codename
(etch, lenny, squeeze, sid) does not change.
To use authenticated apt repositories, multistrap needs to be able to install an
appropriate keyring package from the existing apt sources outside the
into the destination system. Unfortunately, keyring
packages cannot be downloaded from the repositories specified in the
multistrap configuration - this is because "apt" needs the keyring
to be updated before being able to use repositories not previously known.
If relevant packages exist, specify them in the 'keyring' option for each
repository. multistrap will then check that apt has already installed this
package so that the repository can be authenticated before any packages are
downloaded from it.
Note that all
repositories to be used with multistrap must be
authenticated or apt will fail. Similarly, secure apt can only be disabled for
all repositories (by using the --no-auth command line option or setting the
general noauth option in the configuration file), even if only one repository
does not have a suitable keyring available.
The keyring package(s) will also be installed inside the multistrap environment
to match the installed apt sources for the multistrap.
multistrap is stateless - if the directory exists, it will simply proceed as
normal and apt will try to pick up where it left off.
Root Filesystem Configuration¶
multistrap unpacks the downloaded packages but other stages of system
configuration are not attempted. Examples include:
Any device-specific device nodes will also need to be created using MAKEDEV or
"device-table.pl" - a helper script that can work around some of the
issues with MAKEDEV. device-table.pl
requires a device table file along
the lines of the one in the mtd-utils source package. See
Once multistrap has successfully created the basic file and directory layout,
other device-specific scripts are needed before the filesystem can be packaged
up and installed onto the target device.
Once installed, the packages themselves need to be configured using the package
maintainer scripts and "dpkg --configure -a", unless this is a
For "dpkg" to work, /proc
must be mounted (or
is also recommended.
See also: http://wiki.debian.org/Multistrap
To configure the unpacked packages (whether in native or cross mode), certain
environment variables are needed:
Debconf needs to be told to accept that user interaction is not desired:
Perl needs to be told to accept that no locales are available inside the chroot
and not to complain:
LC_ALL=C LANGUAGE=C LANG=C
Then, dpkg can configure the packages:
chroot method (PATH = top directory of chroot):
DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true \
LC_ALL=C LANGUAGE=C LANG=C chroot /PATH/ dpkg --configure -a
at a login shell:
# export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true
# export LC_ALL=C LANGUAGE=C LANG=C
# dpkg --configure -a
(As above, dpkg needs /proc
Native mode - multistrap¶
multistrap was not intended for native support, it was developed for cross
architecture support. In order for multiple repositories to be used,
multistrap only unpacks the packages selected by apt.
In native mode, various post-multistrap operations are likely to be needed that
debootstrap would do for you:
1. copy /etc/hosts into the chroot
2. clean the environment to unset LANGUAGE, LC_ALL and LANG
to silence nuisance perl warnings that obscure other errors
(An alternative to unset the localisation variables is to add locales to your
multistrap configuration file in the 'packages' option.
A native multistrap can be used directly with chroot, so "multistrap"
runs "dpkg --configure -a" at the end of the multistrap process,
unless the ignorenativearch
option is set to true in the General
section of the configuration file.
Daemons in chroots¶
Depending on which system you using to provide the packages for
"multistrap", native chroots should generally not allow daemons to
start inside the chroot. Use the /usr/share/multistrap/chroot.sh
your "setupscript" or include that script in your own setup script.
copes with systems using sysvinit
To support multiple variants of a basic (common) configuration,
"multistrap" allows configuration files to include other (more
general) configuration files. i.e. the most detailed / specific configuration
file is specified on the command line and that file includes another file
which is shared by other configurations.
Specifying just the armel.conf file will get the rest of the settings from
crosschroot.conf so that common changes only need to be made in a single file.
It is strongly
recommended that any changes to the configuration files
involved in any particular cascade are tested using the "--simulate"
option to multistrap which will output a summary of the options that have been
set once the cascade is complete. Note that multistrap does not warn
if a configuration file contains an unrecognised option (for future
compatibility with backported configurations), so a simple typo can result in
an option not being set.
The old packages.conf variables from emsandbox can all be converted into
"multistrap" configuration variables. The machine:variant support in
"multistrap" concentrates on the scripts, config.sh
Note: machine:variant support is likely to be replaced by the hook
functionality described below.
Once "multistrap" has unpacked the downloaded packages, the
"setup.sh" can be called, passing the location and architecture of
the root filesystem, so that other fine tuning can take place. At this stage,
any operations inside a foreign architecture rootfs must not try to execute
any binaries within the rootfs. As the final stage of the multistrap process,
"config.sh" is copied into the root directory of the rootfs.
One advantage of using machine:variant support is that the entire rootfilesystem
can be managed by a single call to multistrap - this is useful when building
root filesystems in userspace.
To enable machine:variant support, specify the path to the scripts to be called
in the variant configuration file (General section):
Ensure that both the setupscript and the configscript are executable or
"multistrap" will ignore the script.
- Example configscript.sh
export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true
export LC_ALL=C LANGUAGE=C LANG=C
dpkg --configure -a
mount proc -t proc /proc
dpkg --configure -a
For more information, see the Wiki: http://wiki.debian.org/Multistrap
- Mounting /dev and /proc for chroot configuration
- /proc can be mounted inside the chroot, as above:
mount proc -t proc /proc
However, /dev should be mounted from outside the chroot, before running any
"configscript.sh" in the chroot:
sudo tar -xzf /path/multistrap.tgz
sudo mount /dev -o bind ./dev/
sudo chroot . ./configscript.sh || true
Restricting package selection¶
"multistrap" includes Required packages by default, the current list
of packages on your own machine can be seen using:
grep-available -FPriority 'required' -sPackage
(The actual list is calculated from the downloaded Packages files and may differ
from the output of "grep-available".)
If the OmitRequired option is set to true, these packages will not be added -
whilst useful, this option can easily lead to a useless rootfs. Only the
packages specified manually in the configuration files will be used in the
calculations - dependencies of those packages will be added but no others.
Adding Priority: important packages¶
"multistrap" can imitate "debootstrap" by automatically
adding all packages from all sections where the downloaded Packages file lists
the package as Priority: important. The default is not to add such packages
unless individually included in a "packages=" option in a section
specified in the "bootstrap" general option. To add all such
packages, set the addimportant option to true in the general section.
Priority: important can only operate for all sections listed in the
"bootstrap" option. This may cause some confusion when mixing
It is not possible to enable addimportant and omitrequired in the same
configuration. "multistrap" will exit with error code 7 if any
configuration results in addimportant and omitrequired both being set to true.
(This includes the effects of including other configuration files.)
The Debian default behaviour after the Lenny release was to consider recommended
packages as extra packages to be installed when any one package is selected.
Recommended packages are those which the maintainer considers that would be
present on "most" installations of that package and allowing
Recommends means allowing Recommends of recommended packages and so on.
The multistrap default is to turn recommends OFF.
Set the allowrecommends option to true in the General section to use typical
"multistrap" supports an option to explicitly set the default release
to use with apt: "aptdefaultrelease". This determines which release
apt will use for the base system packages and is not the same as pinning
(which relates to the use of apt after installation). Multistrap sets the
default-release to the wildcard * unless a release is named in the
"aptdefaultrelease" field. Any release specified here must also be
defined in a stanza referenced in the bootstrap list or apt will fail.
To install a specific version of a package from a newer release than the one
specified as default, "explicitsuite" must also be set to true if
the package exists at any version in the default release. Also, any packages
upon which that package has a strict dependency (i.e. = rather than >=)
must also be explicitly added to the packages line in the stanza for the
desired version, even though that package does not need to be listed to get it
from the default release. This is typical apt behaviour and is not a bug in
The combination of default release, explicit suite and apt preferences can
quickly become complex and bugs can be very hard to identify.
"multistrap" always outputs the complete apt command line, so test
this command yourself (using the files written out by "multistrap")
to see what is going on. Remember that all dependency resolution and all the
logic to determine which version of a specific package gets installed in your
"multistrap" chroot is entirely down to apt and all
"multistrap" can do is pass files and command line options to apt.
See also: apt preferences.
Explicit suite specification¶
Sometimes, apt needs to be told to get a particular package from a particular
suite, ignoring a more recent version in another suite in the same set of
"multistrap" can operate with and without the explicit suite option,
the default is to let apt use the most recent version from the collection of
Explicit suite specification has no effect on the final installed system - if
your aptsources includes a repository which in turn includes a newer version
of the package(s) specified explicitly, the next "apt-get upgrade"
on the device will bring in the newer version.
Also, when specifying packages to get from a specific suite, apt will also try
and ensure that the dependencies for that package are also from the same suite
and this can cause apt to be unable to resolve the complete set of
dependencies. In this situation, being explicit about one package selection
may require being explicit about some (not necessarily all) of the
dependencies of that package as well.
When using this support in Lenny, ensure that each section uses the suite
(oldstable, stable, testing, sid) and not
the codename (etch, lenny,
squeeze, sid) in the "suite" configuration item as the version of
apt in Lenny and previous cannot use the codename.
To test, on Lenny, try:
$ sudo apt-get install apt/stable
$ sudo apt-get install apt/lenny
When using explicitsuite, take care in using stable-proposed-updates or other
temporary locations - if the package migrates into another suite and is
removed from the temporary suite (as with *-proposed-updates), multistrap will
not be able to find the package.
Explicit suite handling can be very hard to get right. In general, it is best to
create a small bootstrap chroot of your native arch, then chroot into it, add
the relevant apt sources and work out exactly what commands are necessary to
get the correct mix of packages. Avoid specifying explicit versions to sort
out problems, work with suites only. Apt preferences / pinning may be useful
here, see Apt preferences.
If a suitable file is listed in the aptpreferences
option of the
section of the configuration file, this file will be copied
into the apt preferences directory of the bootstrap before apt is first used.
When an apt preferences file is
provided, the "Default-Release"
behaviour of "multistrap" is disabled.
As with other external scripts and files, the content of the apt preferences
file is beyond the scope of this manpage. "multistrap" does not try
to verify the supplied file other than ensuring that it can be read.
Omitting deb-src listings¶
Some multistrap environments do not need access to the Debian sources of
packages being installed, typically this is required when preparing a build
(or cross-build) chroot using multistrap.
To turn off this additional source (and save both download time and apt-cache
size), use the omitdebsrc field in each Section.
omitdebsrc is necessary when using packages from debian-ports where packages do
not have sources, except "unreleased".
Foreign architecture bootstraps can operate under "fakeroot"
("multistrap" is designed to do as much as it can within a single
call to make this easier) but the configuration stage which normally happens
with a native architecture bootstrap requires "chroot" and
"chroot" itself will not operate under "fakeroot".
Therefore, if "multistrap" detects that "fakeroot" is in
use, native mode configuration is skipped with a reminder warning.
The same problem applies to "apt-get install" and therefore the
installation of the keyring package on the host system is also skipped if
fakeroot is detected.
Handling problematic packages¶
Sometimes, a particular package will fail to even unpack properly if other
packages have not already been unpacked. This can happen if dpkg diversions
are not setup correctly or if the package Pre-Depends on an executable in
Multistrap offers two ways to handle these problems. A package can be listed as
"reinstall" or as "additional". Each section in the
"multistrap" configuration file can have a single
"reinstall" or "additional" listing or both.
Reinstall means that the package will be downloaded and unpacked as normal -
alongside all the other packages, but will then be reinstalled at the end by
running the "preinst" maintainer script with the "upgrade"
argument. "dpkg" will then continue the rest of the configuration of
Additional adds a second round of "apt-get install" to the multistrap
process - after the initial unpacking. The additional package will then be
downloaded and unpacked. If running natively, the additional package is
downloaded, unpacked and configured after all the rest of the packages have
been downloaded, unpacked and configured.
Neither "reinstall" nor "additional" should be seen as more
than just workarounds and wishlist bugs should be filed in Debian against
packages which require the use of these mechanisms (or the packages which
would prevent the particular package from operating normally).
Adding a debconf seed can help in configuring packages to a particular setting
instead of the package default when running the configuration
non-interactively. See http://www.debian-administration.org/articles/394
information on how to create seed files.
Multiple seed files can be specified using the debconfseed field in the
[General] section, separated by spaces:
Files which do not exist or which cannot be opened will be silently ignored.
Check the results of the parsing using the "--simulate" option to
"multistrap". The preseeding files will be copied to a preseed
directory in /tmp inside the rootfs.
To use the preseeding, add a section to the configscript.sh, prior to any calls
to dpkg --configure -a
. e.g. :
export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true
export LC_ALL=C LANGUAGE=C LANG=C
if [ -d /tmp/preseeds/ ]; then
for file in `ls -1 /tmp/preseeds/*`; do
dpkg --configure -a
If a hook directory (hookdir=) is specified in the General section of the
"multistrap" configuration file, the hook scripts which are
executable will be run from outside the multistrap directory at the following
- download hooks
- Executed before unpacking is started, immediately after the packages have
been downloaded. Download hooks are executable scripts in the specified
hook directory with a filename beginning with download.
- native hooks
- Native hook scripts are executed only in native mode, immediately before
starting the configuration of the downloaded packages and again upon
completion of the package configuration. Native hooks will be called the
absolute path and the current progress state, start or end.
Native scripts are executable scripts in the specified hook directory with a
filename beginning with native.
- completion hooks
- Executed immediately before the tarball is created or
"multistrap" exits if not configured to create a tarball.
Completion scripts are executable scripts in the specified hook directory
with a filename beginning with completion.
Hooks are passed the absolute path to the directory which will be the top level
directory of the chroot or multistrap system. Hooks which cannot be resolved
using realpath or which are not executable will be ignored.
All hooks of one type are sorted into alphabetical order before being run.
Note that "multistrap" does not rollback the effects of hooks in the
case of errors. However, "multistrap" will report the accumulated
errors as warnings. If a hook exits non-zero, the exit value is converted to a
positive number and added to the total warning count, reported at the end of
"multistrap" can produce a lot of output - informational messages
appear on STDOUT, errors and warnings on STDERR. Calls to "apt" and
"dpkg" respect the same pattern, so it is simple to trim the
combined "multistrap" output to just the errors, if desired.
"multistrap" accumulates error states from non-fatal processes within
the operation and reports these as warnings on STDERR as well as exiting with
the accumulated error count. This includes hooks which report non-zero exit
As "multistrap" gets more complex, bugs will creep into the package.
Please report all bugs to the Debian BTS using the "reportbug" tool
attach all configuration files. If your configuration needs
to access local or private apt repositories, please check your configuration
with the latest version of "multistrap" in Debian using the
"--simulate" option and include that report in your bug report.
The "--simulate" option output is regularly expanded to help users
debug problems in the configuration files.
Please also check (and update) the Multistrap wiki at
and the Multistrap webpage content at
before filing bugs. Various people on the
email@example.com mailing list and #emdebian IRC channel on
irc.oftc.net can also help if your config file does not parse correctly. You
would need to put the "--simulate" output on a pastebin website and
put the URL in your message.
Multiarch support is experimental - please report issues and file bugs with full
details of your setup, the full multistrap config file and the errors
"multistrap" overrides the existing multiarch support of the external
system so that a MultiArch aware system can still create a non-MultiArch
chroot from repositories which do not support all of the architectures
supported by the external dpkg.
If multiarch is enabled within the multistrap chroot, "multistrap"
writes out the list into /var/lib/dpkg/arch
inside the chroot.
For multiple architectures, specify the option once and use a space separated
list for the architecture list. Ensure you include what will be the host
architecture of the chroot.
See also http://wiki.debian.org/Multiarch/
multiarch=i386 armel armhf
Each Section will install packages from the base architecture unless the
"Architecture" option is specified for particular sections.
In the "--simulate" output, the architecture(s) specified in the
MultiArch option will be listed under the "Foreign architectures"
listing. Packages for a specific architecture will be listed as the package
name followed by a colon followed by the architecture.