#!/bin/sh

# Create a compressed ramdisk file, based on the directory $REF.
# If $1 (first argument) is "debug", the final filesystem will
# be left in place at $MNT.

# This script has to be run as root, and has therefore been
# kept short and legible, so security conscious people can
# read it and confirm that it only does what it should.

# It calls make_minimal_dev, you should look at that too.

# The filesystem handling half of this script is almost
# straight out of the losetup man page.

# Larry Doolittle   <LRDoolittle@lbl.gov>  September 2000

# configuration:

REF=root
RDSIZE=2400          # RAM disk size in units of kBytes
FILE=image           # final output is $FILE.gz
LOOP=/dev/loop1      # kernel must support loopback
MNT=/mnt/junk        # mount point for loopback device

# No more configuration should be needed below.
# Proofread at will.

HERE=$PWD
PATH=/sbin:/usr/sbin:${PATH}

if [ ! -d $REF ]; then
    echo "$REF is not a directory; check $0 configuration"
    exit 1
fi

if [ ! -d $MNT ]; then
    echo "$MNT is not a directory; check $0 configuration"
    exit 1
fi

dd if=/dev/zero of=$FILE bs=1k count=$RDSIZE  ||  exit
losetup $LOOP $FILE  ||  exit

#  Small filesystems tend not to have enough nodes for a
#  "standard" /dev.  See make_minimal_dev invocation below.
mke2fs -m 0 -i 2048 $LOOP  ||  exit

mount $LOOP $MNT  ||  exit

#  Copy and take ownership of all files that an unprivileged
#  (development) user can create.  See make_root.
cp -a $REF/* $MNT
chown -R root:root $MNT
chown -R 100:100 $MNT/home/mortal
chmod -R g-w $MNT/home/mortal

#  Create the device files
(cd $MNT/dev || exit; sh $HERE/make_minimal_dev) || \
   echo "Warning: Can't make devices in $MNT/dev"

#  Use ldconfig to set up $MNT/etc/ld.so.cache
cp -a /sbin/ldconfig $MNT/sbin
(echo /lib; echo /usr/lib) >$MNT/etc/ld.so.conf
chroot $MNT ldconfig
#  You could rm $MNT/sbin/ldconfig if you were desperate for space,
#  and were sure you'd never want to add libraries at runtime.
#  Doing that properly would require zeroing the file contents first.

test "$1" != "debug"  &&  echo "Unmounting and gzipping $FILE"   && \
umount $MNT   &&   losetup -d $LOOP   &&   gzip -f -9 $FILE   && \
echo "Compressed filesystem $FILE.gz complete, ready for make_floppy"