mmdebstrap ========== An alternative to debootstrap which uses apt internally and is thus able to use more than one mirror and resolve more complex dependencies. Usage ----- Use like debootstrap: sudo mmdebstrap unstable ./unstable-chroot Without superuser privileges: mmdebstrap unstable unstable-chroot.tar With complex apt options: cat /etc/apt/sources.list | mmdebstrap > unstable-chroot.tar For the full documentation use: pod2man ./mmdebstrap | man -l - The sales pitch in comparison to debootstrap -------------------------------------------- Summary: - more than one mirror possible - security and updates mirror included for Debian stable chroots - twice as fast - chroot with apt in 11 seconds - gzipped tarball with apt is 27M small - bit-by-bit reproducible output - unprivileged operation using Linux user namespaces, fakechroot or proot - can operate on filesystems mounted with nodev - foreign architecture chroots with qemu-user - variant installing only Essential:yes packages and dependencies - temporary chroots by redirecting to /dev/null The author believes that a chroot of a Debian stable release should include the latest packages including security fixes by default. This has been a wontfix with debootstrap since 2009 (See #543819 and #762222). Since mmdebstrap uses apt internally, support for multiple mirrors comes for free and stable or oldstable **chroots will include security and updates mirrors**. A side-effect of using apt is being twice as fast as debootstrap. The timings were carried out on a laptop with an Intel Core i5-5200U, using a mirror on localhost and a tmpfs. | variant | mmdebstrap | debootstrap | | --------- | ---------- | ------------ | | essential | 9.52 s | n.a | | apt | 10.98 s | n.a | | minbase | 13.54 s | 26.37 s | | buildd | 21.31 s | 34.85 s | | - | 23.01 s | 48.83 s | Apt considers itself an `Essential: yes` package. This feature allows one to create a chroot containing just the `Essential: yes` packages and apt (and their hard dependencies) in **just 11 seconds**. If desired, a most minimal chroot with just the `Essential: yes` packages and their hard dependencies can be created with a gzipped tarball size of just 34M. By using dpkg's `--path-exclude` option to exclude documentation, even smaller gzipped tarballs of 21M in size are possible. If apt is included, the result is a **gzipped tarball of only 27M**. These small sizes are also achieved because apt caches and other cruft is stripped from the chroot. This also makes the result **bit-by-bit reproducible** if the `$SOURCE_DATE_EPOCH` environment variable is set. The author believes, that it should not be necessary to have superuser privileges to create a file (the chroot tarball) in one's home directory. Thus, mmdebstrap provides multiple options to create a chroot tarball with the right permissions **without superuser privileges**. Depending on what is available, it uses either Linux user namespaces, fakechroot or proot. Debootstrap supports fakechroot but will not create a tarball with the right permissions by itself. Support for Linux user namespaces and proot is missing (see bugs #829134 and #698347, respectively). When creating a chroot tarball with debootstrap, the temporary chroot directory cannot be on a filesystem that has been mounted with nodev. In unprivileged mode, **mknod is never used**, which means that /tmp can be used as a temporary directory location even if if it's mounted with nodev as a security measure. If the chroot architecture cannot be executed by the current machine, qemu-user is used to allow one to create a **foreign architecture chroot**. Limitations in comparison to debootstrap ---------------------------------------- Debootstrap supports creating a Debian chroot on non-Debian systems but mmdebstrap requires apt and is thus limited to Debian and derivatives. There is no `SCRIPT` argument. The following options, don't exist: `--second-stage`, `--exclude`, `--resolve-deps`, `--force-check-gpg`, `--merged-usr` and `--no-merged-usr`. Tests ===== The script `coverage.sh` runs mmdebstrap in all kind of scenarios to execute all code paths of the script. It verifies its output in each scenario and displays the results gathered with Devel::Cover. It also compares the output of mmdebstrap with debootstrap in several scenarios. To run the testsuite, run: ./make_mirror.sh CMD=./mmdebstrap ./coverage.sh To also generate perl Devel::Cover data, omit the `CMD` environment variable. But that will also take a lot longer. The `make_mirror.sh` script will be a no-op if nothing changed in Debian unstable. You don't need to run `make_mirror.sh` before every invocation of `coverage.sh`. When you make changes to `make_mirror.sh` and want to regenerate the cache, run: touch -d yesterday shared/cache/debian/dists/unstable/Release The script `coverage.sh` does not need an active internet connection by default. An online connection is only needed by the `make_mirror.sh` script which fills a local cache with a few minimal Debian mirror copies. By default, `coverage.sh` will skip running a single test which tries creating a Ubuntu Focal chroot. To not skip that test, run `coverage.sh` with the environment variable `ONLINE=yes`. Bugs ==== mmdebstrap has bugs. Report them here: https://gitlab.mister-muffin.de/josch/mmdebstrap/issues Contributors ============ - Johannes Schauer (main author) - Helmut Grohne - Benjamin Drung - Steve Dodd