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 The sales pitch in comparison to debootstrap -------------------------------------------- Summary: - more than one mirror possible - security and updates mirror included for Debian stable chroots - 3-6 times faster - 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 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 **3-6 times faster** than debootstrap. The timings were carried out on a laptop with an Intel Core i5-5200U. | variant | mmdebstrap | debootstrap | | ------- | ---------- | ------------ | | minbase | 14.18 s | 51.47 s | | buildd | 20.55 s | 59.38 s | | - | 18.98 s | 127.18 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. There is no `SCRIPT` argument. There is no `--second-stage` option. Tests ===== The script `test.sh` compares the output of mmdebstrap with debootstrap in several scenarios. Since debootstrap needs superuser privileges, `test.sh` needs `sudo` to run. 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. Due to a whacky setup and to also test root mode, this script needs superuser privileges. Bugs ==== mmdebstrap has bugs. Report them here: https://gitlab.mister-muffin.de/josch/mmdebstrap/issues