See also Multistrap

Customising Rootfs

For the embedded context an optional rootfs-config script can be run after the rootfs has been generated, because often /etc/fstab, /etc/inittab, /etc/hosts, /etc/securetty, /etc/modules (for example) need to be modified before the rootfs will boot enough to be configured.

Here is an example script (as used on balloon3):

set -e -x

# Emdebian grip compatibility version
# variant tcl-sl40

#pass path to the root. Don't let it run without one as it will break your system
if [ "" = "$1" ] ; then 
  echo "You need to specify a path to the target rootfs"
  if [ -e "$1" ] ; then
    echo "Root dir $ROOTFS not found"

if [ "/" = "ROOTFS" ] ; then echo "Refusing to change your build system's files" ; fi

#Do things that need to be done at 1st stage so that rootfs will boot.

#Set securetty
#Add modules - e.g. to support USB serial/ethernet console

# specify config to use
if [ "" = "$2" ] ; then 
if [ -d "$2" ] ; then
  echo "Config dir $CONFIG not found"

#read in settings for $CONSOLE
if [ -e config ] ; then
  . config

   #add serial ports to securetty - now idempotent
DONECONSOLE=`grep $CONSOLE $ROOTFS/etc/securetty || true`
if [ -z "$DONECONSOLE" ]; then
  echo "$CONSOLE" >> $ROOTFS/etc/securetty
DONETELNET=`grep pts/0 $ROOTFS/etc/securetty || true`
if [ -z "$DONETELNET" ]; then
  echo "pts/0" >> $ROOTFS/etc/securetty
   #put our standard fstab and network and modules files in
if [ ! -d $ROOTFS/etc/network ]; then mkdir -p $ROOTFS/etc/network; fi
if [ ! -d $ROOTFS/etc/init.d ]; then mkdir -p $ROOTFS/etc/init.d; fi
if [ ! -d $ROOTFS/etc/dhcp3 ]; then mkdir -p $ROOTFS/etc/dhcp3; fi
if [ ! -d $ROOTFS/etc/apt/apt.conf.d/ ]; then 
  mkdir -p $ROOTFS/etc/apt/apt.conf.d/
cp -v $CONFIG/fstab $ROOTFS/etc/fstab
cp -v $CONFIG/interfaces $ROOTFS/etc/network/interfaces
cp -v $CONFIG/modules $ROOTFS/etc/modules
cp -v $CONFIG/dhclient.conf $ROOTFS/etc/dhcp3/
cp -v $CONFIG/urandom $ROOTFS/etc/init.d/
cp -v $CONFIG/inittab $ROOTFS/etc/
cp -v $CONFIG/10disablerecommends $ROOTFS/etc/apt/apt.conf.d/
   # make sure sudo uses group sudo by default
rm -f $ROOTFS/etc/sudoers
cp -v $CONFIG/sudoers $ROOTFS/etc/
chmod 400 $ROOTFS/etc/sudoers
   # creating devices
(cd $ROOTFS/dev; /dev/MAKEDEV -v fb )
(cd $ROOTFS/dev; /dev/MAKEDEV -v ttyS0 ttyS1 ttyS2 )
(cd $ROOTFS/dev; /dev/MAKEDEV -v sd )
(cd $ROOTFS/dev; /dev/MAKEDEV -v mtd )
(cd $ROOTFS/dev; mknod rtc c 253 0 )
   #mutter - it makes mtd butnot mtdblock - patch MAKEDEV?
(cd $ROOT/FSdev; /dev//MAKEDEV -v mtdblock{0..7})
(cd $ROOTFS/dev; mkdir -p mtdblock; for DEVICE in 0 1 2 3 4 5 6 7; do mknod mtdblock/$DEVICE b 31 $DEVICE; done)
   # making devices so far missing between old and new multistrap versions preventing
   # chroot from running into newly untarred rootfs
(cd $ROOTFS/dev; /dev/MAKEDEV -v std )
(cd $ROOTFS/dev; /dev/MAKEDEV -v fd )
(cd $ROOTFS/dev; /dev/MAKEDEV -v ptmx )
   # tidy up after old multistrap code
if [ -f $ROOTFS/etc/apt/sources.list.d/sources.list ]; then
   rm -v $ROOTFS/etc/apt/sources.list.d/sources.list
#set hostname
echo sl40 > $ROOTFS/etc/hostname
#be nice to put these in the right places in files (perl -pi?)
echo "       localhost.localdomain   localhost" > ${ROOTFS}/etc/hosts
echo "       sl40   sl40" >> ${ROOTFS}/etc/hosts