View source for Linux: Debian: Minimal ARM filesystem

== Overview ==
Debian Linux for ARM processors provides thousands of software packages. CompuLab provides minimal Debian filesystem that can be used as a basis for custom filesystem creation. The minimal filesystem packages include archive of basic Debian system created with [http://linux.die.net/man/8/debootstrap debootsrap].

== Suites ==
The basic Debian system is available for the following Debian suites:
* [http://www.compulab.co.il/workspace/sw/debian/releases/lenny-minimal-armel.tar.bz2 Lenny] - [http://www.debian.org/releases/stable/ stable]
* [http://www.compulab.co.il/workspace/sw/debian/releases/squeeze-minimal-armel.tar.bz2 Squeeze] - [http://www.debian.org/releases/testing/ testing]
* [http://www.compulab.co.il/workspace/sw/debian/releases/sid-minimal-armel.tar.bz2 Sid] - [http://www.debian.org/releases/unstable/ unstable]

== Custom filesystem development ==
The basic Debian system allows development of custom filesystem images either on-target in NFS-rooted environment or on-host using QEMU ARM emulation.

=== NFS-rooted environment ===
* Extract the basic Debian filesystem to a directory on the host workstation and export that directory through NFS:
 mkdir -p /path/to/armel/debian/sid
 cd /path/to/armel/debian/sid
 sudo tar xjvf /path/to/sid-minimal-armel.tar.bz2
 sudo sh -c 'echo "/path/to/armel/debian/sid 192.168.0.0/24(rw,no_root_squash,sync)" >> /etc/exports'
 sudo exportfs -a
* Ensure that kernel command line contains parameters required to boot the target system with root on NFS, for example
 setenv bootargs "root=/dev/nfs nfsroot=<hostip>:/path/to/armel/debian/sid ip=dhcp console=ttyS2,38400"
* Boot the target.
* Login as {{parameter|root}}, password {{cmd|111111}}
* Use [http://linux.die.net/man/8/apt-get apt-get] package handling utility to install required packages

== QEMU environment ==
* Setup binfmt_misc support and statically built QEMU as described in [[Linux:_Development_for_ARM_modules#Chroot_with_QEMU|Chroot with QEMU]] section of the [[Linux:_Development_for_ARM_modules|Linux Development for ARM modules]] article.
* Extract the basic Debian filesystem to a directory on the host workstation
 mkdir -p /path/to/armel/debian/sid
 cd /path/to/armel/debian/sid
 sudo tar xjvf /path/to/sid-minimal-armel.tar.bz2
* Copy static QEMU into the basic Debian system:
 cp /path/to/static/qemu-arm* /path/to/armel/debian/sid/usr/local/bin
* Enter the ARM Debian environment:
  sudo chroot /path/to/armel/debian/sid /bin/sh
* Use [http://linux.die.net/man/8/apt-get apt-get] package handling utility to install required packages

== Deployment ==

=== Reducing target filesystem size ===
{{Warning|The following commands must be executed on target or in chroot'ed environment. Execution of the below commands on the host system may severely damage it!}}
* Remove packages that were automatically installed to satisfy dependencies for some package and that are no more needed
 apt-get --purge autoremove
* Remove packages that are not needed on the target system, for example:
 apt-get purge man
* Clean local repository of retrieved package files
 apt-get clean
* If the target is not intended to run package management tools remove Debian package databases:
 find  /var/lib/dpkg/ /var/lib/apt -type f -exec rm {} \;
* Remove unneeded data in {{filename|/usr/share}}, for instance
 rm -fr /usr/share/doc/ /usr/share/info/

=== Creating NAND flash image ===
After the filesystem modifications are complete follow the [[Linux_Development_for_XScale_modules#Creating_NAND_flash_images|Creating NAND flash images]] guide to create an image ready for deployment onto the system NAND flash.

== See also ==
* [[Linux: Development for ARM modules]]
* [[CM-X300: Linux: Debian]]
* [http://www.aurel32.net/info/debian_arm_qemu.php Debian on an emulated ARM machine]
* [http://wiki.debian.org/ArmEabiPort ArmEabiPort - Debian Wiki]