NAME¶

mmdebstrap - multi-mirror Debian chroot creation

SYNOPSIS¶

mmdebstrap [OPTION...] [SUITE [TARGET [MIRROR...]]]

DESCRIPTION¶

mmdebstrap creates a Debian chroot of SUITE into TARGET from one or more MIRRORs. It is meant as an alternative to the debootstrap tool (see section DEBOOTSTRAP). In contrast to debootstrap it uses apt to resolve dependencies and is thus able to use more than one mirror and resolve more complex dependencies.

If no MIRROR option is provided, <http://deb.debian.org/debian> is used. If SUITE is a stable release name and no MIRROR is specified, then mirrors for updates and security are automatically added. If a MIRROR option starts with "deb " or "deb-src " then it is used as a one-line-style format entry for apt's sources.list inside the chroot. If a MIRROR option contains a "://" then it is interpreted as a mirror URI and the apt line inside the chroot is assembled as "deb [arch=A] B C D" where A is the host's native architecture, B is the MIRROR, C is the given SUITE and D is the components given via --components (defaults to "main"). If a MIRROR option happens to be an existing file, then its contents are pasted into the chroot's sources.list. This can be used to supply a deb822 style sources.list. If MIRROR is "-" then standard input is pasted into the chroot's sources.list. More than one mirror can be specified and are appended to the chroot's sources.list in the given order. If you specify a https or tor MIRROR and you want the chroot to be able to update itself, don't forget to also install the ca-certificates package, the apt-transport-https package for apt versions less than 1.5 and/or the apt-transport-tor package using the --include option, as necessary.

The optional TARGET argument can either be the path to a directory, the path to a tarball filename, the path to a squashfs image, the path to an ext2 image, a FIFO, a character special device, or "-". Without the --format option, TARGET will be used to choose the format. See the section FORMATS for more information. If no TARGET was specified or if TARGET is "-", an uncompressed tarball will be sent to standard output.

The SUITE may be a valid release code name (eg, sid, stretch, jessie) or a symbolic name (eg, unstable, testing, stable, oldstable). Any suite name that works with apt on the given mirror will work. If no SUITE was specified, then a single MIRROR "-" is added and thus the information of the desired suite has to come from standard input as part of a valid apt sources.list file. The value of the SUITE argument will be used to determine which apt index to use for finding out the set of "Essential:yes" packages and/or the set of packages with the right priority for the selected variant. See the section VARIANTS for more information.

All status output is printed to standard error unless --logfile is used to redirect it to a file or --quiet or --silent is used to suppress any output on standard error. Help and version information will be printed to standard error with the --help and --version options, respectively. Otherwise, an uncompressed tarball might be sent to standard output if TARGET is "-" or if no TARGET was specified.

OPTIONS¶

Options are case insensitive. Short options may be bundled. Long options require a double dash and may be abbreviated to uniqueness.

-h,--help

Print synopsis and options of this man page and exit.

--man

Show the full man page as generated from Perl POD in a pager. This requires the perldoc program from the perl-doc package. This is the same as running:

    pod2man /usr/bin/mmdebstrap | man -l -
    

--version

Print the mmdebstrap version and exit.

--variant=name

Choose which package set to install. Valid variant names are extract, custom, essential, apt, required, minbase, buildd, important, debootstrap, -, and standard. The default variant is debootstrap. See the section VARIANTS for more information.

--mode=name

Choose how to perform the chroot operation and create a filesystem with ownership information different from the current user. Valid mode names are auto, sudo, root, unshare, fakeroot, fakechroot, proot and chrootless. The default mode is auto. See the section MODES for more information.

--format=name

Choose the output format. Valid format names are auto, directory, tar, squashfs, ext2 and null. The default format is auto. See the section FORMATS for more information.

--aptopt=option|file

Pass arbitrary options to apt. Will be permamently added to /etc/apt/apt.conf.d/99mmdebstrap inside the chroot. Use hooks for temporary configuration options. Can be specified multiple times. Each option will be appended to 99mmdebstrap. A semicolon will be added at the end of the option if necessary. If the command line argument is an existing file, the content of the file will be appended to 99mmdebstrap verbatim.

Example: This is necessary for allowing old timestamps from snapshot.debian.org

    --aptopt='Acquire::Check-Valid-Until "false"'
    --aptopt='Apt::Key::gpgvcommand "/usr/libexec/mmdebstrap/gpgvnoexpkeysig"'
    

Example: Settings controlling download of package description translations

    --aptopt='Acquire::Languages { "environment"; "en"; }'
    --aptopt='Acquire::Languages "none"'
    

Example: Enable installing Recommends (by default mmdebstrap doesn't)

    --aptopt='Apt::Install-Recommends "true"'
    

Example: Configure apt-cacher or apt-cacher-ng as an apt proxy

    --aptopt='Acquire::http { Proxy "http://127.0.0.1:3142"; }'
    

Example: For situations in which the apt sandbox user cannot access the chroot

    --aptopt='APT::Sandbox::User "root"'
    

Example: Minimizing the number of packages installed from experimental

    --aptopt='APT::Solver "aspcud"'
    --aptopt='APT::Solver::aspcud::Preferences
       "-count(solution,APT-Release:=/a=experimental/),-removed,-changed,-new"'
    

--keyring=file|directory

Change the default keyring to use by apt. By default, /etc/apt/trusted.gpg and /etc/apt/trusted.gpg.d are used. Depending on whether a file or directory is passed to this option, the former and latter default can be changed, respectively. Since apt only supports a single keyring file and directory, respectively, you can not use this option to pass multiple files and/or directories. Using the "--keyring" argument in the following way is equal to keeping the default:

    --keyring=/etc/apt/trusted.gpg --keyring=/etc/apt/trusted.gpg.d
    

If you need to pass multiple keyrings, use the "signed-by" option when specifying the mirror like this:

    mmdebstrap mysuite out.tar "deb [signed-by=/path/to/key.gpg] http://..."
    

The "signed-by" option will automatically be added to the final "sources.list" if the keyring required for the selected SUITE is not yet trusted by apt. Automatically adding the "signed-by" option in these cases requires "gpg" to be installed. If "gpg" and "ubuntu-archive-keyring" are installed, then you can create a Ubuntu Bionic chroot on Debian like this:

    mmdebstrap bionic ubuntu-bionic.tar
    

The resulting chroot will have a "source.list" with a "signed-by" option pointing to /usr/share/keyrings/ubuntu-archive-keyring.gpg.

--dpkgopt=option|file

Pass arbitrary options to dpkg. Will be permanently added to /etc/dpkg/dpkg.cfg.d/99mmdebstrap inside the chroot. Use hooks for temporary configuration options. Can be specified multiple times. Each option will be appended to 99mmdebstrap. If the command line argument is an existing file, the content of the file will be appended to 99mmdebstrap verbatim.

Example: Exclude paths to reduce chroot size

    --dpkgopt='path-exclude=/usr/share/man/*'
    --dpkgopt='path-include=/usr/share/man/man[1-9]/*'
    --dpkgopt='path-exclude=/usr/share/locale/*'
    --dpkgopt='path-include=/usr/share/locale/locale.alias'
    --dpkgopt='path-exclude=/usr/share/doc/*'
    --dpkgopt='path-include=/usr/share/doc/*/copyright'
    --dpkgopt='path-include=/usr/share/doc/*/changelog.Debian.*'
    --dpkgopt='path-exclude=/usr/share/{doc,info,man,omf,help,gnome/help}/*'
    

--include=pkg1[,pkg2,...]

Comma or whitespace separated list of packages which will be installed in addition to the packages installed by the specified variant. The direct and indirect hard dependencies will also be installed. The behaviour of this option depends on the selected variant. The extract and custom variants install no packages by default, so for these variants, the packages specified by this option will be the only ones that get either extracted or installed by dpkg, respectively. For all other variants, apt is used to install the additional packages. Package names are directly passed to apt and thus, you can use apt features like "pkg/suite", "pkg=version", "pkg-", use a glob or regex for "pkg" or use apt patterns. See apt(8) for the supported syntax. The option can be specified multiple times and the packages are concatenated in the order in which they are given on the command line. If later list items are repeated, then they get dropped so that the resulting package list is free of duplicates. So the following are equivalent:

    --include="pkg1/stable pkg2=1.0 pkg3-"
    --include=pkg1/stable,pkg2=1.0,pkg3-
    --incl=pkg1/stable --incl="pkg2=1.0 pkg3-" --incl=pkg2=1.0,pkg3-
    

--components=comp1[,comp2,...]

Comma or whitespace separated list of components like main, contrib and non-free which will be used for all URI-only MIRROR arguments. The option can be specified multiple times and the components are concatenated in the order in which they are given on the command line. If later list items are repeated, then they get dropped so that the resulting component list is free of duplicates. So the following are equivalent:

    --components="main contrib non-free"
    --components=main,contrib,non-free
    --comp=main --comp="contrib non-free" --comp="main,non-free"
    

--architectures=native[,foreign1,...]

Comma or whitespace separated list of architectures. The first architecture is the native architecture inside the chroot. The remaining architectures will be added to the foreign dpkg architectures. Without this option, the native architecture of the chroot defaults to the native architecture of the system running mmdebstrap. The option can be specified multiple times and values are concatenated. If later list items are repeated, then they get dropped so that the resulting list is free of duplicates. So the following are equivalent:

    --architectures="amd64 armhf mipsel"
    --architectures=amd64,armhf,mipsel
    --arch=amd64 --arch="armhf mipsel" --arch=armhf,mipsel
    

--simulate, --dry-run

Run apt-get with --simulate. Only the package cache is initialized but no binary packages are downloaded or installed. Use this option to quickly check whether a package selection within a certain suite and variant can in principle be installed as far as their dependencies go. If the output is a tarball, then no output is produced. If the output is a directory, then the directory will be left populated with the skeleton files and directories necessary for apt to run in it. No hooks are executed in with --simulate or --dry-run.

--setup-hook=command

Execute arbitrary commands right after initial setup (directory creation, configuration of apt and dpkg, ...) but before any packages are downloaded or installed. At that point, the chroot directory does not contain any executables and thus cannot be chroot-ed into. See section HOOKS for more information.

Example: Setup chroot for installing a sub-essential busybox-based chroot with --variant=custom --include=dpkg,busybox,libc-bin,base-files,base-passwd,debianutils

    --setup-hook='mkdir -p "$1/bin"'
    --setup-hook='for p in awk cat chmod chown cp diff echo env grep less ln
        mkdir mount rm rmdir sed sh sleep sort touch uname mktemp; do
        ln -s busybox "$1/bin/$p"; done'
    --setup-hook='echo root:x:0:0:root:/root:/bin/sh > "$1/etc/passwd"'
    --setup-hook='printf "root:x:0:\nmail:x:8:\nutmp:x:43:\n" > "$1/etc/group"'
    

For a more elegant way for setting up a sub-essential busybox-based chroot, see the --hook-dir option below.

--extract-hook=command

Execute arbitrary commands after the Essential:yes packages have been extracted but before installing them. See section HOOKS for more information.

Example: Install busybox symlinks

    --extract-hook='chroot "$1" /bin/busybox --install -s'
    

--essential-hook=command

Execute arbitrary commands after the Essential:yes packages have been installed but before installing the remaining packages. The hook is not executed for the extract and custom variants. See section HOOKS for more information.

Example: Enable unattended upgrades

    --essential-hook='echo unattended-upgrades
        unattended-upgrades/enable_auto_updates boolean true
        | chroot "$1" debconf-set-selections'
    

Example: Select Europe/Berlin as the timezone

    --essential-hook='echo tzdata tzdata/Areas select Europe
        | chroot "$1" debconf-set-selections'
    --essential-hook='echo tzdata tzdata/Zones/Europe select Berlin
        | chroot "$1" debconf-set-selections'
    

--customize-hook=command

Execute arbitrary commands after the chroot is set up and all packages got installed but before final cleanup actions are carried out. See section HOOKS for more information.

Example: Preparing a chroot for use with autopkgtest

    --customize-hook='chroot "$1" passwd --delete root'
    --customize-hook='chroot "$1" useradd --home-dir /home/user
        --create-home user'
    --customize-hook='chroot "$1" passwd --delete user'
    --customize-hook='echo host > "$1/etc/hostname"'
    --customize-hook='echo "127.0.0.1 localhost host" > "$1/etc/hosts"'
    --customize-hook=/usr/share/autopkgtest/setup-commands/setup-testbed
    

--hook-directory=directory

Execute scripts in directory with filenames starting with "setup", "extract", "essential" or "customize", at the respective stages during an mmdebstrap run. The files must be marked executable. Their extension is ignored. Subdirectories are not traversed. This option is a short-hand for specifying the remaining four hook options individually for each file in the directory. If there are more than one script for a stage, then they are added alphabetically. This is useful in cases, where a user wants to run the same hooks frequently. For example, given a directory "./hooks" with two scripts "setup01-foo.sh" and "setup02-bar.sh", this call:

    mmdebstrap --customize=./scriptA --hook-dir=./hooks --setup=./scriptB
    

is equivalent to this call:

    mmdebstrap --customize=./scriptA --setup=./hooks/setup01-foo.sh \
        --setup=./hooks/setup02-bar.sh --setup=./scriptB
    

The option can be specified multiple times and scripts are added to the respective hooks in the order the options are given on the command line. Thus, if the scripts in two directories depend upon each other, the scripts must be placed into a common directory and be named such that they get added in the correct order.

Example 1: Run mmdebstrap with eatmydata

    --hook-dir=/usr/share/mmdebstrap/hooks/eatmydata
    

Example 2: Setup chroot for installing a sub-essential busybox-based chroot

    --hook-dir=/usr/share/mmdebstrap/hooks/busybox
    

Example 3: Automatically mount all directories referenced by "file://" mirrors into the chroot

    --hook-dir=/usr/share/mmdebstrap/hooks/file-mirror-automount
    

--skip=stage[,stage,...]

mmdebstrap tries hard to implement sensible defaults and will try to stop you before shooting yourself in the foot. This option is for when you are sure you know what you are doing and allows one to skip certain actions and safety checks. See section OPERATION for a list of possible arguments and their context.

-q,--quiet, -s,--silent

Do not write anything to standard error. If used together with --verbose or --debug, only the last option will take effect.

-v,--verbose

Instead of progress bars, write the dpkg and apt output directly to standard error. If used together with --quiet or --debug, only the last option will take effect.

-d,--debug

In addition to the output produced by --verbose, write detailed debugging information to standard error. Errors will print a backtrace. If used together with --quiet or --verbose, only the last option will take effect.

--logfile=filename

Instead of writing status information to standard error, write it into the file given by filename.

MODES¶

Creating a Debian chroot requires not only permissions for running chroot but also the ability to create files owned by the superuser. The selected mode decides which way this is achieved.

auto

This mode automatically selects a fitting mode. If the effective user id is the one of the superuser, then the sudo mode is chosen. Otherwise, the unshare mode is picked if the system has the sysctl "kernel.unprivileged_userns_clone" set to 1. Should that not be the case and if the fakechroot binary exists, the fakechroot mode is chosen. Lastly, the proot mode is used if the proot binary exists.

sudo, root

This mode directly executes chroot and is the same mode of operation as is used by debootstrap. It is the only mode that can directly create a directory chroot with the right permissions. If the chroot directory is not accessible by the _apt user, then apt sandboxing will be automatically disabled. This mode needs to be able to mount and thus requires "SYS_CAP_ADMIN".

unshare

This mode uses Linux user namespaces to allow unprivileged use of chroot and creation of files that appear to be owned by the superuser inside the unshared namespace. A tarball created in this mode should be bit-by-bit identical to a tarball created with the root mode.

A directory chroot created with this mode will end up with wrong ownership information. For correct ownership information, the directory must be accessed from a user namespace with the right subuid/subgid offset, like so:

    $ lxc-usernsexec -- lxc-unshare -s 'MOUNT|PID|UTSNAME|IPC' -- \
    > /usr/sbin/chroot ./debian-rootfs /bin/bash
    

Or without LXC:

    $ mmdebstrap --unshare-helper /usr/sbin/chroot ./debian-rootfs /bin/bash
    

Or, if you don't mind using superuser privileges and have systemd-nspawn available and you know your subuid/subgid offset (100000 in this example):

    $ sudo systemd-nspawn --private-users=100000 \
    > --directory=./debian-rootfs /bin/bash
    

If this mode is used as the root user, the user namespace is not unshared (but the mount namespace and other still are) and created directories will have correct ownership information. This is also useful in cases where the root user wants the benefits of an unshared mount namespace to prevent accidentally messing up the system.

fakeroot, fakechroot

This mode will exec mmdebstrap again under "fakechroot fakeroot". A directory chroot created with this mode will end up with wrong permissions. If you need a directory then run mmdebstrap under "fakechroot fakeroot -s fakeroot.env" and use "fakeroot.env" later when entering the chroot with "fakechroot fakeroot -i fakeroot.env chroot ...". This mode will not work if maintainer scripts are unable to handle "LD_PRELOAD" correctly like the package initramfs-tools until version 0.132. This mode will also not work with a different libc inside the chroot than on the outside. See the section LIMITATIONS in fakechroot(1).

proot

This mode will carry out all calls to chroot with proot instead. Since ownership information is only retained while proot is still running, this will lead to wrong ownership information in the final directory (everything will be owned by the user that executed mmdebstrap) and tarball (everything will be owned by the root user). Extended attributes are not retained. This mode is useful if you plan to use the chroot with proot.

chrootless

Uses the dpkg option "--force-script-chrootless" to install packages into TARGET without dpkg and apt inside TARGET but using apt and dpkg from the machine running mmdebstrap. Maintainer scripts are run without chrooting into TARGET and rely on their dependencies being installed on the machine running mmdebstrap. Only very few packages support this mode. Namely, as of 2021, not all essential packages support it, mainly due to missing support in debconf. See https://wiki.debian.org/Teams/Dpkg/Spec/InstallBootstrap or the dpkg-root-support usertag of debian-dpkg@lists.debian.org in the Debian bug tracking system. WARNING: if this option is used carelessly with packages that do not support "DPKG_ROOT", this mode can result in undesired changes to the system running mmdebstrap because maintainer-scripts will be run without chroot(1).

VARIANTS¶

All package sets also include the direct and indirect hard dependencies (but not recommends) of the selected package sets. The variants minbase, buildd and -, resemble the package sets that debootstrap would install with the same --variant argument. The release with a name matching the SUITE argument as well as the native architecture will be used to determine the "Essential:yes" and priority values. To select packages with matching priority from any suite, specify the empty string for SUITE. The default variant is debootstrap.

extract

Installs nothing by default (not even "Essential:yes" packages). Packages given by the "--include" option are extracted but will not be installed.

custom

Installs nothing by default (not even "Essential:yes" packages). Packages given by the "--include" option will be installed. If another mode than chrootless was selected and dpkg was not part of the included package set, then this variant will fail because it cannot configure the packages.

essential

"Essential:yes" packages.

apt

The essential set plus apt.

required, minbase

The essential set plus all packages with Priority:required and apt. It is roughly equivalent to running mmdebstrap with

    --variant=essential --include="?priority(required)"
    

buildd

The minbase set plus build-essential. It is roughly equivalent to running mmdebstrap with

    --variant=essential --include="?priority(required),build-essential"
    

important, debootstrap, -

The required set plus all packages with Priority:important. This is the default of debootstrap. It is roughly equivalent to running mmdebstrap with

    --variant=essential --include="~prequired|~pimportant"
    

standard

The important set plus all packages with Priority:standard. It is roughly equivalent to running mmdebstrap with

    --variant=essential --include="~prequired|~pimportant|~pstandard"
    

FORMATS¶

The output format of mmdebstrap is specified using the --format option. Without that option the default format is auto. The following formats exist:

auto

When selecting this format (the default), the actual format will be inferred from the TARGET positional argument. If TARGET was not specified, then the tar format will be chosen. If TARGET happens to be /dev/null or if standard output is /dev/null, then the null format will be chosen. If TARGET is an existing directory, and does not equal to "-", then the directory format will be chosen. If TARGET ends with ".tar" or with one of the filename extensions listed in the section COMPRESSION, or if TARGET equals "-", or if TARGET is a named pipe (fifo) or if TARGET is a character special file, then the tar format will be chosen. If TARGET ends with ".squashfs" or ".sqfs", then the squashfs format will be chosen. If <TARGET> ends with ".ext2" then the ext2 format will be chosen. If none of these conditions apply, the directory format will be chosen.

directory, dir

A chroot directory will be created in TARGET. If the directory already exists, it must either be empty or only contain an empty "lost+found" directory. The special TARGET "-" does not work with this format because a directory cannot be written to standard output. If you need your directory be named "-", then just explicitly pass the relative path to it like ./-. If a directory is chosen as output in any other mode than sudo, then its contents will have wrong ownership information and special device files will be missing. Refer to the section MODES for more information.

tar

A temporary chroot directory will be created in $TMPDIR or /tmp if $TMPDIR is not set. A tarball of that directory will be stored in TARGET or sent to standard output if TARGET was omitted or if TARGET equals "-". If TARGET ends with one of the filename extensions listed in the section COMPRESSION, then a compressed tarball will be created. The tarball will be in POSIX 1003.1-2001 (pax) format and will contain extended attributes. To preserve the extended attributes, you have to pass --xattrs --xattrs-include='*' to tar when extracting the tarball.

squashfs, sqfs

A temporary chroot directory will be created in $TMPDIR or /tmp if $TMPDIR is not set. A tarball of that directory will be piped to the "tar2sqfs" utility, which will create an xz compressed squashfs image with a blocksize of 1048576 bytes in TARGET. The special TARGET "-" does not work with this format because "tar2sqfs" can only write to a regular file. If you need your squashfs image be named "-", then just explicitly pass the relative path to it like ./-. The "tar2sqfs" tool only supports a limited set of extended attribute prefixes. Therefore, extended attributes are disabled in the resulting image. If you need them, create a tarball first and remove the extended attributes from its pax headers. Refer to the EXAMPLES section for how to achieve this.

ext2

A temporary chroot directory will be created in $TMPDIR or /tmp if $TMPDIR is not set. A tarball of that directory will be piped to the "genext2fs" utility, which will create an ext2 image that will be approximately 90% full in TARGET. The special TARGET "-" does not work with this format because "genext2fs" can only write to a regular file. If you need your ext2 image be named "-", then just explicitly pass the relative path to it like ./-. To convert the result to an ext3 image, use "tune2fs -O has_journal TARGET" and to convert it to ext4, use "tune2fs -O extents,uninit_bg,dir_index,has_journal TARGET". Since "genext2fs" does not support extended attributes, the resulting image will not contain them.

null

A temporary chroot directory will be created in $TMPDIR or /tmp if $TMPDIR is not set. After the bootstrap is complete, the temporary chroot will be deleted without being part of the output. This is most useful when the desired artifact is generated inside the chroot and it is transferred using special hooks such as sync-out. It is also useful in situations where only the exit code or stdout or stderr of a process run in a hook is of interest.

HOOKS¶

This section describes properties of the hook options --setup-hook, --extract-hook, --essential-hook and --customize-hook which are common to all four of them. Any information specific to each hook is documented under the specific hook options in the section OPTIONS.

The options can be specified multiple times and the commands are executed in the order in which they are given on the command line. There are four different types of hook option arguments. If the argument passed to the hook option starts with "copy-in", "copy-out", "tar-in", "tar-out", "upload" or "download" followed by a space, then the hook is interpreted as a special hook. Otherwise, if command is an existing executable file from $PATH or if command does not contain any shell metacharacters, then command is directly exec-ed with the path to the chroot directory passed as the first argument. Otherwise, command is executed under sh and the chroot directory can be accessed via $1. Most environment variables set by mmdebstrap (like "DEBIAN_FRONTEND", "LC_ALL" and "PATH") are preserved. Most notably, "APT_CONFIG" is being unset. If you need the path to "APT_CONFIG" as written by mmdebstrap it can be found in the "MMDEBSTRAP_APT_CONFIG" environment variable. All environment variables set by the user are preserved, except for "TMPDIR" which is cleared. See section TMPDIR. Furthermore, "MMDEBSTRAP_MODE" will store the mode set by --mode, "MMDEBSTRAP_HOOK" stores which hook is currently run (setup, extract, essential, customize) and "MMDEBSTRAP_VERBOSITY" stores the numerical verbosity level (0 for no output, 1 for normal, 2 for verbose and 3 for debug output).

In special hooks, the paths inside the chroot are relative to the root directory of the chroot. The path on the outside is relative to current directory of the original mmdebstrap invocation. The path inside the chroot must already exist. Paths outside the chroot are created as necessary.

In fakechroot and proot mode, "tar", or "sh" and "cat" have to be run inside the chroot or otherwise, symlinks will be wrongly resolved and/or permissions will be off. This means that the special hooks might fail in fakechroot and proot mode for the setup hook or for the extract and custom variants if no "tar" or "sh" and "cat" is available inside the chroot.

copy-out pathinside [pathinside ...] pathoutside

Recursively copies one or more files and directories recursively from pathinside inside the chroot to pathoutside outside of the chroot.

copy-in pathoutside [pathoutside ...] pathinside

Recursively copies one or more files and directories into the chroot into, placing them into pathinside inside of the chroot.

sync-out pathinside pathoutside

Recursively copy everything inside pathinside inside the chroot into pathoutside. In contrast to copy-out, this command synchronizes the content of pathinside with the content of pathoutside without deleting anything from pathoutside but overwriting content as necessary. Use this command over copy-out if you don't want to create a new directory outside the chroot but only update the content of an existing directory.

sync-in pathoutside pathinside

Recursively copy everything inside pathoutside into pathinside inside the chroot. In contrast to copy-in, this command synchronizes the content of pathoutside with the content of pathinside without deleting anything from pathinside but overwriting content as necessary. Use this command over copy-in if you don't want to create a new directory inside the chroot but only update the content of an existing directory.

tar-in outside.tar pathinside

Unpacks a tarball outside.tar from outside the chroot into a certain location pathinside inside the chroot.

tar-out pathinside outside.tar

Packs the path pathinside from inside the chroot into a tarball, placing it into a certain location outside.tar outside the chroot.

download fileinside fileoutside

Copy the file given by fileinside from inside the chroot to outside the chroot as fileoutside. In contrast to copy-out, this command only handles files and not directories. To copy a directory recursively out of the chroot, use copy-out or tar-out. Its advantage is, that by being able to specify the full path on the outside, including the filename, the file on the outside can have a different name from the file on the inside. In contrast to copy-out and tar-out, this command follows symlinks.

upload fileoutside fileinside

Copy the file given by fileoutside from outside the chroot to inside the chroot as fileinside. In contrast to copy-in, this command only handles files and not directories. To copy a directory recursively into the chroot, use copy-in or tar-in. Its advantage is, that by being able to specify the full path on the inside, including the filename, the file on the inside can have a different name from the file on the outside. In contrast to copy-in and tar-in, permission and ownership information will not be retained.

OPERATION¶

This section gives an overview of the different steps to create a chroot.

check

Upon startup, several checks are carried out, like:

setup

The following tasks are carried out unless --skip=setup is used:

setup-hook

Run --setup-hook options and all setup* scripts in --hook-dir.

update

Runs "apt-get update" using the temporary apt configuration file created in the setup step. This can be disabled using --skip=update.

download

In the extract and custom variants, "apt-get install" is used to download all the packages requested via the --include option. The apt variant uses the fact that libapt treats the "apt" packages as implicitly essential to download only all "Essential:yes" packages plus apt using "apt-get dist-upgrade". In the remaining variants, all Packages files downloaded by the update step are inspected to find the "Essential:yes" package set as well as all packages of the required priority.

extract

Extract the downloaded packages into the rootfs.

extract-hook

Run --extract-hook options and all extract* scripts in --hook-dir.

prepare

In fakechroot mode, environment variables "LD_LIBRARY_PATH" will be set up correctly. If the chroot requires the qemu-user-static binary it will be copied in. For foreign fakechroot environments, "LD_LIBRARY_PATH" and "QEMU_LD_PREFIX" are set up accordingly. This step is not carried out in extract mode and neither for the chrootless variant.

essential

Uses "dpkg --install" to properly install all packages that have been extracted before. Removes all packages downloaded in the download step, except those which were present in /var/cache/apt/archives/ before (if any). This can be disabled using --skip=essential/unlink. This step is not carried out in extract mode.

essential-hook

Run --essential-hook options and all essential* scripts in --hook-dir. This step is not carried out in extract mode.

install

Install the apt package into the chroot, if necessary and then run apt from inside the chroot to install all remaining packages. This step is not carried out in extract mode.

customize-hook

Run --customize-hook options and all customize* scripts in --hook-dir. This step is not carried out in extract mode.

cleanup

Performs cleanup tasks, unless --skip=cleanup is used:

EXAMPLES¶

Use like debootstrap:

    $ sudo mmdebstrap unstable ./unstable-chroot

Without superuser privileges:

    $ mmdebstrap unstable unstable-chroot.tar

With no command line arguments at all. The chroot content is entirely defined by a sources.list file on standard input.

    $ mmdebstrap < /etc/apt/sources.list > unstable-chroot.tar

Since the tarball is output on stdout, members of it can be excluded using tar on-the-fly. For example the /dev directory can be removed from the final tarbal in cases where it is to be extracted by a non-root user who cannot create device nodes:

    $ mmdebstrap unstable | tar --delete ./dev > unstable-chroot.tar

Create a tarball for use with "sbuild --chroot-mode=unshare":

    $ mmdebstrap --variant=buildd unstable ~/.cache/sbuild/unstable-amd64.tar

Instead of a tarball, a squashfs image can be created:

    $ mmdebstrap unstable unstable-chroot.squashfs

By default, mmdebstrap runs tar2sqfs with "--no-skip --exportable --compressor xz --block-size 1048576". To choose a different set of options, and to filter out all extended attributes not supported by tar2sqfs, pipe the output of mmdebstrap into tar2sqfs manually like so:

    $ mmdebstrap unstable \
        | mmtarfilter --pax-exclude='*' \
            --pax-include='SCHILY.xattr.user.*' \
            --pax-include='SCHILY.xattr.trusted.*' \
            --pax-include='SCHILY.xattr.security.*' \
        | tar2sqfs --quiet --no-skip --force --exportable --compressor xz \
            --block-size 1048576 unstable-chroot.squashfs

By default, debootstrapping a stable distribution will add mirrors for security and updates to the sources.list.

    $ mmdebstrap stable stable-chroot.tar

If you don't want this behaviour, you can override it by manually specifying a mirror in various different ways:

    $ mmdebstrap stable stable-chroot.tar http://deb.debian.org/debian
    $ mmdebstrap stable stable-chroot.tar "deb http://deb.debian.org/debian stable main"
    $ mmdebstrap stable stable-chroot.tar /path/to/sources.list
    $ mmdebstrap stable stable-chroot.tar - < /path/to/sources.list

Drop locales (but not the symlink to the locale name alias database), translated manual packages (but not the untranslated ones), and documentation (but not copyright and Debian changelog).

    $ mmdebstrap --variant=essential \
        --dpkgopt='path-exclude=/usr/share/man/*' \
        --dpkgopt='path-include=/usr/share/man/man[1-9]/*' \
        --dpkgopt='path-exclude=/usr/share/locale/*' \
        --dpkgopt='path-include=/usr/share/locale/locale.alias' \
        --dpkgopt='path-exclude=/usr/share/doc/*' \
        --dpkgopt='path-include=/usr/share/doc/*/copyright' \
        --dpkgopt='path-include=/usr/share/doc/*/changelog.Debian.*' \
        unstable debian-unstable.tar

Create a bootable USB Stick that boots into a full Debian desktop:

    $ mmdebstrap --aptopt='Apt::Install-Recommends "true"' --customize-hook \
        'chroot "$1" adduser --gecos user --disabled-password user' \
        --customize-hook='echo 'user:live' | chroot "$1" chpasswd' \
        --customize-hook='echo host > "$1/etc/hostname"' \
        --customize-hook='echo "127.0.0.1 localhost host" > "$1/etc/hosts"' \
        --include=linux-image-amd64,task-desktop unstable debian-unstable.tar
    $ cat << END > extlinux.conf
    > default linux
    > timeout 0
    >
    > label linux
    > kernel /vmlinuz
    > append initrd=/initrd.img root=LABEL=rootfs
    END
    # You can use $(sudo blockdev --getsize64 /dev/sdXXX) to get the right
    # image size for the target medium in bytes
    $ guestfish -N debian-unstable.img=disk:8G -- \
        part-disk /dev/sda mbr : \
        part-set-bootable /dev/sda 1 true : \
        set-label /dev/sda1 rootfs : \
        mkfs ext4 /dev/sda1 : mount /dev/sda1 / : \
        tar-in debian-unstable.tar / xattrs:true : \
        upload /usr/lib/EXTLINUX/mbr.bin /boot/mbr.bin : \
        copy-file-to-device /boot/mbr.bin /dev/sda size:440 : \
        extlinux / : copy-in extlinux.conf / : sync : umount / : shutdown
    $ qemu-system-x86_64 -m 1G -enable-kvm debian-unstable.img
    $ sudo dd if=debian-unstable.img of=/dev/sdXXX status=progress

On architectures without extlinux you can also boot using grub2:

    $ mmdebstrap --include=linux-image-amd64,grub2,systemd-sysv unstable fs.tar
    $ guestfish -N debian-unstable.img=disk:2G -- \
        part-disk /dev/sda mbr : \
        part-set-bootable /dev/sda 1 true : \
        set-label /dev/sda1 rootfs : \
        mkfs ext4 /dev/sda1 : mount /dev/sda1 / : \
        tar-in fs.tar / xattrs:true : \
        command "grub-install /dev/sda" : \
        command update-grub : \
        sync : umount / : shutdown
    $ qemu-system-x86_64 -m 1G -enable-kvm debian-unstable.img

Build libdvdcss2.deb without installing installing anything or changing apt sources on the current system:

    $ mmdebstrap --variant=apt --components=main,contrib --include=libdvd-pkg \
        --customize-hook='chroot $1 /usr/lib/libdvd-pkg/b-i_libdvdcss.sh' \
        | tar --extract --verbose --strip-components=4 \
            --wildcards './usr/src/libdvd-pkg/libdvdcss2_*_*.deb'
    $ ls libdvdcss2_*_*.deb

Use as replacement for autopkgtest-build-qemu and vmdb2:

    $ mmdebstrap --variant=important --include=linux-image-amd64 \
        --customize-hook='chroot "$1" passwd --delete root' \
        --customize-hook='chroot "$1" useradd --home-dir /home/user --create-home user' \
        --customize-hook='chroot "$1" passwd --delete user' \
        --customize-hook='echo host > "$1/etc/hostname"' \
        --customize-hook='echo "127.0.0.1 localhost host" > "$1/etc/hosts"' \
        --customize-hook=/usr/share/autopkgtest/setup-commands/setup-testbed \
        unstable debian-unstable.tar
    $ cat << END > extlinux.conf
    > default linux
    > timeout 0
    >
    > label linux
    > kernel /vmlinuz
    > append initrd=/initrd.img root=/dev/vda1 rw console=ttyS0
    END
    $ guestfish -N debian-unstable.img=disk:8G -- \
        part-disk /dev/sda mbr : \
        part-set-bootable /dev/sda 1 true : \
        mkfs ext4 /dev/sda1 : mount /dev/sda1 / : \
        tar-in debian-unstable.tar / xattrs:true : \
        upload /usr/lib/EXTLINUX/mbr.bin /boot/mbr.bin : \
        copy-file-to-device /boot/mbr.bin /dev/sda size:440 : \
        extlinux / : copy-in extlinux.conf / : sync : umount / : shutdown
    $ qemu-img convert -O qcow2 debian-unstable.img debian-unstable.qcow2

As a debootstrap wrapper to run it without superuser privileges but using Linux user namespaces instead. This fixes Debian bug #829134.

    $ mmdebstrap --variant=custom --mode=unshare \
        --setup-hook='env container=lxc debootstrap unstable "$1"' \
        - debian-debootstrap.tar

Build a non-Debian chroot like Ubuntu bionic:

    $ mmdebstrap --aptopt='Dir::Etc::Trusted
       "/usr/share/keyrings/ubuntu-keyring-2012-archive.gpg"' bionic bionic.tar

If, for some reason, you cannot use a caching proxy like apt-cacher or apt-cacher-ng, you can use the sync-in and sync-out special hooks to synchronize a directory outside the chroot with /var/cache/apt/archives inside the chroot.

    $ mmdebstrap --variant=apt --skip=essential/unlink \
        --setup-hook='mkdir -p ./cache "$1"/var/cache/apt/archives/' \
        --setup-hook='sync-in ./cache /var/cache/apt/archives/' \
        --customize-hook='sync-out /var/cache/apt/archives ./cache' \
        unstable /dev/null

Instead of copying potentially large amounts of data with sync-in you can also use a bind-mount in combination with a "file://" mirror to make packages from the outside available inside the chroot:

    $ mmdebstrap --variant=apt --skip=essential/unlink \
        --setup-hook='mkdir "$1/tmp/mirror"' \
        --setup-hook='mount -o ro,bind /tmp/mirror "$1/tmp/mirror"' \
        --customize-hook='sync-out /var/cache/apt/archives ./cache' \
        --customize-hook='umount "$1/tmp/mirror"; rmdir "$1/tmp/mirror";' \
        unstable /dev/null file:///tmp/mirror http://deb.debian.org/debian

To automatically mount all directories referenced by "file://" mirrors into the chroot you can use a hook:

    $ mmdebstrap --variant=apt \
        --hook-dir=/usr/share/mmdebstrap/hooks/file-mirror-automount \
        unstable /dev/null file:///tmp/mirror1 file:///tmp/mirror2

Create a system that can be used with docker:

    $ mmdebstrap unstable | sudo docker import - debian
    [...]
    $ sudo docker run -it --rm debian whoami
    root
    $ sudo docker rmi debian

Create a system that can be used with podman:

    $ mmdebstrap unstable | podman import - debian
    [...]
    $ podman run --network=none -it --rm debian whoami
    root
    $ podman rmi debian

As a docker/podman replacement:

    $ mmdebstrap unstable | mmtarfilter --path-exclude='/dev/*' > chroot.tar
    [...]
    $ mmdebstrap --variant=custom --skip=update \
        --setup-hook='tar-in chroot.tar /' \
        --customize-hook='chroot "$1" whoami' unstable /dev/null
    [...]
    root
    $ rm chroot.tar

You can re-use a chroot tarball created with mmdebstrap for further refinement. Say you want to create a minimal chroot and a chroot with more packages installed, then instead of downloading and installing the essential packages twice you can instead build on top of the already present minimal chroot:

    $ mmdebstrap --variant=apt unstable chroot.tar
    $ mmdebstrap --variant=custom --setup-hook \
        'mmtarfilter "--path-exclude=/dev/*" < chroot.tar | tar -C "$1" -x' \
        --customize-hook='chroot "$1" apt-get install --yes pkg1 pkg2' \
        '' chroot-full.tar

ENVIRONMENT VARIABLES¶

"SOURCE_DATE_EPOCH"

By setting "SOURCE_DATE_EPOCH" the result will be reproducible across multiple runs with the same options and mirror content. Note that for debootstrap compatibility, mmdebstrap will copy the host's /etc/resolv.conf and /etc/hostname into the chroot. This means that the mmdebstrap output will differ if it is run on machines with differing /etc/resolv.conf and /etc/hostname contents. To make the result reproducible across different hosts, you need to manually either delete both files from the output:

    $ mmdebstrap --customize-hook='rm "$1"/etc/resolv.conf' \
                 --customize-hook='rm "$1"/etc/hostname' ...
    

or fill them with reproducible content:

    $ mmdebstrap --customize-hook='echo nameserver X > "$1"/etc/resolv.conf' \
                 --customize-hook='echo host > "$1"/etc/hostname' ...
    

"TMPDIR"

When creating a tarball, a temporary directory is populated with the rootfs before the tarball is packed. The location of that temporary directory will be in /tmp or the location pointed to by "TMPDIR" if that environment variable is set. Setting "TMPDIR" to a different directory than /tmp is useful if you have /tmp on a tmpfs that is too small for your rootfs.

If you set "TMPDIR" in unshare mode, then the unshared user must be able to access the directory. This means that the directory itself must be world-writable and all its ancestors must be at least world-executable.

Since "TMPDIR" is only valid outside the chroot, the variable is being unset when running hook scripts. If you need a valid temporary directory in a hook, consider using /tmp inside your target directory.

DEBOOTSTRAP¶

This section lists some differences to debootstrap.

• More than one mirror possible
• Default mirrors for stable releases include updates and security mirror
• Multiple ways to operate as non-root: fakechroot, proot, unshare
• twice as fast
• Can create a chroot with only "Essential:yes" packages and their deps
• Reproducible output by default if $SOURCE_DATE_EPOCH is set
• Can create output on filesystems with nodev set
• apt cache and lists are cleaned at the end
• foreign architecture chroots using qemu-user

Limitations in comparison to debootstrap:

• Only runs on systems with apt installed (Debian and derivatives)
• No SCRIPT argument (use hooks instead)
• Some debootstrap options don't exist, namely:

  --second-stage, --exclude, --resolve-deps, --force-check-gpg, --merged-usr and --no-merged-usr

MERGED-/USR¶

mmdebstrap will create a merged-/usr chroot or not depending on whether packages setting up merged-/usr (i.e. the usrmerge package) are installed or not. In Debian, the essential package init-system-helpers is will depend on the usrmerge package, starting with Debian 12 (Bookworm).

Before Debian 12 (Bookworm), to force mmdebstrap to create a chroot with merged-/usr using symlinks, either explicitly install the usrmerge package:

    --include=usrmerge

or setup merged-/usr using the debootstrap-method which takes care of the architecture specific symlinks and installs the usr-is-merged package.

    --hook-dir=/usr/share/mmdebstrap/hooks/merged-usr

To force mmdebstrap to create a chroot without merged-/usr even after the Debian 12 (Bookworm) release, you can use the following hook:

    --hook-dir=/usr/share/mmdebstrap/hooks/no-merged-usr

This will write "this system will not be supported in the future" into /etc/unsupported-skip-usrmerge-conversion inside the chroot and install the usr-is-merged package to avoid the installation of the usrmerge package and its dependencies.

COMPRESSION¶

mmdebstrap will choose a suitable compressor for the output tarball depending on the filename extension. The following mapping from filename extension to compressor applies:

 extension compressor
 --------------------
 .tar      none
 .gz       gzip
 .tgz      gzip
 .taz      gzip
 .Z        compress
 .taZ      compress
 .bz2      bzip2
 .tbz      bzip2
 .tbz2     bzip2
 .tz2      bzip2
 .lz       lzip
 .lzma     lzma
 .tlz      lzma
 .lzo      lzop
 .lz4      lz4
 .xz       xz
 .txz      xz
 .zst      zstd

To change compression specific options, either use the respecitve environment variables like XZ_OPT or send mmdebstrap output to your compressor of choice with a pipe.

BUGS¶

https://gitlab.mister-muffin.de/josch/mmdebstrap/issues

https://bugs.debian.org/src:mmdebstrap

As of version 1.20.9, dpkg does not provide facilities preventing it from reading the dpkg configuration of the machine running mmdebstrap. Therefore, until this dpkg limitation is fixed, a default dpkg configuration is recommended on machines running mmdebstrap. If you are using mmdebstrap as the non-root user, then as a workaround you could run "chmod 600 /etc/dpkg/dpkg.cfg.d/*" so that the config files are only accessible by the root user. See Debian bug #808203.

With apt versions before 2.1.16, setting "[trusted=yes]" or "Acquire::AllowInsecureRepositories "1"" to allow signed archives without a known public key or unsigned archives will fail because of a gpg warning in the apt output. Since apt does not communicate its status via any other means than human readable strings, and because mmdebstrap wants to treat transient network errors as errors, mmdebstrap treats any warning from "apt-get update" as an error.

SEE ALSO¶

    debootstrap(8)