Debian Rootfs

How to make a Debian root filesystem for the Sim.One using debootstrap

Updated Mar 1, 2011 by

Making a Debian root filesystem for the Sim.One using debootstrap

Here's one way to make a Debian root filesystem for the Sim.One.

I prepare the root filesystem on some fast host, then transfer it to the Sim.One to complete the installation.

Create the base system on some other computerPrepare the media

Here, I'm using a USB pendrive, whose single partition appears as /dev/sda1; If you use an SD card, it'll be /dev/mmcblk0p1 instead. Although the final filesystem is under 128MB, you'll need a 256MB device to be able to create it.

mkfs -t ext2 -b 1024 -m 0 /dev/sda1

• -t ext2: use the fastest Linux filesystem available
• -b 1024: use the smallest blocksize because read/writes are slow
• -m 0: Don't reserve 10% for root-only use as there is not much space anyway.

Don't periodically check already-clean volumes because it is time-consuming

tune2fs -c 0 -i 0 /dev/sda1

Make the new medium visible on your host computer

mkdir /mnt/sda1
mount /dev/sda1 /mnt/sda1Create a "foreign" Debian filesystem

Dump an initial filesystem onto the medium, up to the point where you need to run native programs on a real ARM processor

debootstrap --arch armel --foreign squeeze /mnt/sda1 http://ftp.debian.org/debian

Change directory into the new root filesystem

cd /mnt/sda1

Zap some configurations that were copied from the host system

echo simone > etc/hostname
> etc/resolv.conf

Create missing devices in the static /dev

mknod dev/ttyAM0 c 204 16
mknod dev/rtc0 c 254 0
ln -s rtc0 dev/rtc
mknod dev/mmcblk0 b 179 0
mknod dev/mmcblk0p1 b 179 1
mknod dev/sda b 8 0
mknod dev/sda1 b 8 1

Install the kernel modules into the root filesystem. If you have compiled your own kernel you can use:

cd ~/linux-simone/linux-2.6.36
INSTALL_MOD_PATH=/mnt/sda1 make modules_install
rm /mnt/sda1/lib/modules/*/{build,source}

or if you downloaded the kernel image you should fetch its modules tarball and unpack it into the Debian root filesystem:

cd
wget http://sim1.googlecode.com/files/modules-2.6.36-debian-20101118.tgz
tar xzf modules-2.6.36-debian-20101118.tgz -C /mnt/sda1

If you don't need the modules, you will at least need to cd out of /mnt/sda1 so that you can unmount it.

Now unmount the storage and wait for the prompt to return before unplugging it

umount /mnt/sda1Complete the installation on the Sim.OneBoot the base system

Now move the pendrive to one of the Sim.One's USB sockets and boot it into a single-user shell, talking to it over the serial port at 57600 baud.

The following settings are for a USB pendrive. If your root filesystem is on an SD card, use root=/dev/mmcblk0p1 instead.

First load a Debian EABI kernel. Here is my setup to fetch it from a file called "uImage" on a tftp server:

SIM.ONE> set ipaddr 10.0.0.51
SIM.ONE> set netmask 255.255.255.0
SIM.ONE> set serverip 10.0.0.1
SIM.ONE> set bootfile uImage
SIM.ONE> set bootcmd 'tftp c0200000; bootm'
SIM.ONE> set bootargs console=ttyAM0 root=/dev/sda1 rootwait mmc_core.use_spi_crc=0
SIM.ONE> saveenv

alternatively, you can write the image to flash memory:

SIM.ONE> set ipaddr 10.0.0.51
SIM.ONE> set netmask 255.255.255.0
SIM.ONE> set serverip 10.0.0.1
SIM.ONE> erase 60080000 6027ffff
SIM.ONE> tftp 60080000 uImage
SIM.ONE> set bootcmd bootm 60080000
SIM.ONE> set bootargs console=ttyAM0 root=/dev/sda1 rootwait mmc_core.use_spi_crc=0
SIM.ONE> saveenv

Just this once, we want it to boot into a single-user shell:

SIM.ONE> set bootargs console=ttyAM0 root=/dev/sda1 rootwait mmc_core.use_spi_crc=0 init=/bin/sh
SIM.ONE> bootComplete the base installation

When you get the shell prompt on the Sim.One, set up the environment and install the core packages. On an SD card, this step takes just under an hour. On USB pendrive under half an hour. It's time to take a break!

debootstrap/debootstrap --second-stage

This is the point at which maximum filespace is used: 218428 KB.

If, during this step, you get I/O errors from the USB storage or "USB disconnect" messages on the console, it may be that you are using Sim.One hardware before v1.4 and have not set it to access the RAM in 16-bit mode. Fetch u-boot-*-16bit.bin from the Downloads page

wget http://sim1.googlecode.com/files/u-boot-1.1.6-simone-20091201-16bit.bin

and program it with the "download" utility as described on the wiki page at the section "EP9307 loader" -> "Programming the U-Boot loader into Flash".

Clean up after debootstrapapt-get cleanSet the date

If the real-time clock is not set correctly, you might like to do so now. Here we set it to 12:45 on the 1st March 2011

date 030112452011Create kernel module indices

If you installed the modules (above) from your own kernel compilation, you will need to build the module index files before kernel module loading will work. The module tarballs should have had this step performed already, but you can do it anyway to make sure; it takes about 4 minutes.

depmod -aCreate basic configurations

Filesystem mount table

cat > etc/fstab << \EOF
# /etc/fstab: static file system information.
#
#            
/dev/root       /               auto    defaults        0       1
proc            /proc           proc    defaults        0       0
EOF

Arrange for a login shell to be started on the serial port

cat >> /etc/inittab << \EOF
# Serial port of Sim.One
#
S0:23:respawn:/sbin/getty -L ttyAM0 57600 vt100
EOF

and allow root logins on it

echo ttyAM0 >> /etc/securetty

If this filesystem is for personal use, you probably want to set a root password at this point.

passwd

For the distribution instead, we clear the root password

passwd -d root

Arrange for the audio modules to be loaded at system startup

echo snd-soc-simone >> /etc/modules

Configure the network to set up the loopback interface and to have the ethernet auto-configure with DHCP

cat >> /etc/network/interfaces << \EOF

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp
# Generate a unique locally-assigned MAC address from CPU serial number
pre-up ifconfig eth0 hw ether `sed -n 's/^Serial.* 000000/02/p' /proc/cpuinfo`
EOF

Remove a bogus directory that was created during the installation of udev

rm -r /dev/.udev

Now boot into the proper system

exec /sbin/init

and log in as root

simone login: root

Set up the software package management system. You might prefer to use a local mirror such as ftp.it.debian.org - see for a complete list - and for the latest in multimedia you might also like to add deb squeeze main

cat > /etc/apt/sources.list << \EOF
deb http://ftp.debian.org/debian squeeze main
deb http://security.debian.org squeeze/updates main
deb http://simplemachines.it/debian armel-squeeze+crunch/
EOF
apt-get update
apt-get upgrade

Adding these package lists makes a new high-water mark for filesystem size of 229519KB.

Save space

Install localepurge to save 30 MB of multi-language message translations. Press Enter at "Do you want to continue?" and go ahead with "No locales" when it asks: Tab Enter Tab Enter.

apt-get install localepurge   # Filesystem size -> 246360KB
localepurge

Remove downloaded copies of packages (again!)

apt-get clean

If you like, you can remove the documentation, leaving the directory structure so that future apt-get install operations won't fail due to missing directories. I don't do this in the standard distribution.

find /usr/share/man ! -type d -print0 | xargs -0 rm
apt-get remove --purge info man-db      # Do you want to continue [Y/n]? [Enter]
rm -r /usr/share/doc/*
rm /usr/share/info/*.gz
rm `find /etc/alternatives -name '*.gz'`

Remove pointless backups, log files and temporary files

rm /usr/share/info/dir.old
rm /var/cache/debconf/*.dat-old
rm /var/log/{bootstrap,dpkg}.log
rm /var/log/*.{gz,?}
rm -r /tmp/*
for a in /var/log/{*.log,apt/*.log,debug,dmesg,faillog,messages,syslog,wtmp}
do
    > $a
done

If you're making a system to distribute, you can also remove the downloaded package lists

rm /var/cache/apt/* /var/lib/apt/lists/*

All done. Close down and celebrate.

halt

The final size of the filesystem without the package lists is 109330 Kbytes. Removing the documentation leaves about 70MB.