Reducing the size of the Debian Installation Footprint

It may be useful to reduce the size of the installation footprint on Embedded systems, or on older computers or laptops with limited drive space, or in cases where a small installation is preferred. Minimal systems in general also carry security benefits because fewer packages means that there are fewer security exploits available.

Remove non-critical packages

The following packages are non-critical and can be removed:

The following packages cannot be removed, even though marked as optional:

# Remove non-critical packages (don't remove busybox -> don't sure if this ist still a problem on debian 7)
# ~i -> list all installed packages
# !~M -> don't list automatic installed packages
# !~prequired -> don't list packages with priority required
# !~pimportant -> don't list packages with priority important
# !~R~prequired -> don't list dependency packages of required packages
# !~R~pimportant -> don't list dependency packages of important packages
# !~R~R~prequired -> don't list dependency packages of dependency packages of required packages -.- (two levels should be enough. Have not found a recursive option)
# !~R~R~pimportant -> ... required packages
# !busybox -> don't list busybox
# !grub -> don't list grub (we need a boot manager. If LILO or something else is used change this)
# !initramfs-tools -> don't list initramfs-tools (else the kernel is gone)

apt-get purge $(aptitude search '~i!~M!~prequired!~pimportant!~R~prequired!~R~R~prequired!~R~pimportant!~R~R~pimportant!busybox!grub!initramfs-tools' | awk '{print $2}')
apt-get purge aptitude
apt-get autoremove
apt-get clean

Reconfigure apt so that it does not install additional packages

Add the following entries to the /etc/apt/apt.conf configuration file:

APT::Install-Recommends "0" ; APT::Install-Suggests "0" ;

Replace packages with smaller equivalents

Remove unwanted files at install time

Unwanted files, like most of the files from the following sections, can be removed at install time by using dpkg filters, see dpkg(1) --path-exclude and --path-include options.

Remove unnecessary packages in general

Apt has an inbuilt feature to remove files that are no longer required by your system. Run the following command to remove unnecessary packages:

# apt autoremove

Unfortunately, apt does not always manage to find and purge all unused files. This can be a problem particularly when a program has been installed outside of apt (such as with make install). Therefore, the best solution to removing unnecessary packages is to not install them in the first place.

deborphan is a useful package for finding any other unnecessary packages in the system. To find such packages run:

deborphan --guess-all

Be careful when removing suggested packages, as they may have package dependencies that may still required by your system.

Packages can be deleted manually if needed be and you know what you are doing. Just be sure to know exactly what is being removed by checking the packages information:

apt show <package name>

When removing packages, make sure to not break Debian!

Remove unnecessary locale files

The introduction of LanguagePacks (tdebs) may also help in reducing the size of the installation footprint.

Note: See the dpkg filters.

Remove foreign language man files

With appropriate privileges, it is possible to remove the foreign man pages as follows:

rm -rf /usr/share/man/??
rm -rf /usr/share/man/??_*

Note: See the dpkg filters.

Remove unnecessary kernel modules

Build a smaller kernel using fewer options

Reduce the size of the X installation footprint

Reduce the size of the initramfs

create /etc/initramfs-tools/conf.d/compress with the content

COMPRESS=xz

Remove unnecessary ipv6 files

If you are using only [ipv4] internally, then the following [ipv6] files can be removed:

Remove /etc/alternatives

If your applications have been mapped using traditional methods, then it is possible to remove the /etc/alternatives directory.

/!\ The gain is extremely minor, and there's no much point in doing this.

Replace the getty processes with the ngetty single process daemon

The getty processes can be replaced by the ngetty single process daemon to reduce virtual memory utilization:

Use busybox built-ins instead of full packages

You can use the tiny busybox tools instead of installing full packages. Run busybox to see which applets are available. man busybox gives you details on each applets and which parameters are supported. e.g. busybox df starts the df applet from busybox.

Add busybox less to the Debian Alternatives System as pager

Debian Alternatives System doesn't link to two words like "busybox less". If you just create a symbolic link in /usr/local/bin (ln -s /bin/busybox /usr/local/bin/less) then every time you call less, busybox less will be started since echo $PATH

The solution is to create a shell script named busybox.less that calls "busybox less $@".

cd /usr/local/bin
echo /bin/busybox less \$\@ >busybox.less
chmod +x busybox.less
echo 'export PAGER="pager" >>/etc/profile
#pager without -s because busybox less doesn't support -s (--squeeze-blank-lines), default is "pager -s"
update-alternatives --install /usr/bin/pager pager /usr/local/bin/busybox.less 40 \
          --slave /usr/share/man/man1/pager.1.gz pager.1.gz /usr/share/man/man1/busybox.1.gz
update-alternatives --config pager #activate "busybox less" manually

Rebuilding packages using the Tiny C Compiler

Rebuilding packages using the Tiny C Compiler does not reduce size of packages. Differences between tcc and gcc

Compress binaries/libraries using UPX

If they don't reside on btrfs with transparent filesystem compresssion on. Do this with care, some systems are not supported by UPX, and some binaries break. See: https://packages.debian.org/upx-ucl