#!/bin/bash
# Shell script to prepare a root FS image based on the Novell/SUSE rescue
# image source.  You must have a xen kernel installed for this to work.
# (c) Kurt Garloff <garloff@suse.de>, 2005-01-24, GNU GPL
# Maintained by Charles Coffing <ccoffing@novell.com>
#
# TODO:
# - trap SIGINT and clean up
# - can't know that /sbin/depmod will work with this rescue image
# - support domUloader
# - check for disk full in exchange_kernel_modules

MB_DEFAULT=88

usage()
{
    echo "Usage:"
    echo "  mk-xen-rescue-img.sh source destination [MB [kernelver]]"
    echo "Purpose:"
    echo "  Creates a root filesystem and an associated config file for a Xen-compatible"
    echo "  Linux virtual machine."
    echo "Arguments:"
    echo "  * 'source' is the source from which to copy files.  Normally, this is"
    echo "    the SUSE rescue image, such as /media/cdrom/boot/x86_64/rescue,"
    echo "    but it could also be an already-mounted root filesystem."
    echo "  * 'destination' is the pathname of a disk image to be created, based on"
    echo "    'source'."
    echo "  * 'MB' is the size of disk image (default $MB_DEFAULT)."
    echo "  * 'kernelver' is the version of an installed Xen-compatible Linux kernel"
    echo "    (from the kernel-xen package) to install in the disk image.  If not"
    echo "    specified, the newest of those currently installed will be selected."
    exit 2
}

usage_error()
{
    echo "Error:  $@"
    echo ""
    usage
}

error()
{
    echo "Error:  $@"
    if [ ! -z "$DST_MNT" ]; then
        umount "$DST_MNT"
        rmdir "$DST_MNT"
    fi
    exit 1
}

cp_error()
{
    error "Failed to copy files to '$DST'."
}

# Determine Xen kernel version
get_xen_kernel()
{
    if [ -z "$KVER" ]; then
        KVER="`cd /lib/modules && ls -td *-xen/kernel | head -n1 | sed 's@/kernel@@'`"
    else
        if [ ! -d /lib/modules/$KVER/kernel ]; then
            error "/lib/modules/$KVER/kernel does not exist."
        fi
    fi
    if [ -z "$KVER" ]; then
        error "You need to have a 'kernel-xen' package installed."
    fi
}

cp_rescue()
{
    local LSRC=$1
    local LDST=$2

    # The rescue image has empty directories all hard-linked to the same
    # thing, probably to conserve inodes.  This gives 'cp' heartburn.
    # I want hard linked directories to be created separately (i.e.,
    # dereferenced), but I don't want to dereference soft links.
    # 'tar' handles this nicely.

    (cd "$LSRC" && tar --atime-preserve --one-file-system -cf - *) | \
    (cd "$LDST" && tar -xmf -)
}

# Create FS and copy rescue FS
create_basis_and_mount()
{
    echo "Creating disk image within '$DST'..."
    dd if=/dev/zero of="$DST" bs=4096 count=1 2>/dev/null >/dev/null 2>&1
    dd if=/dev/zero of="$DST" bs=1048576 count=0 seek=$MB >/dev/null 2>&1
    /sbin/mke2fs -b 1024 -i 2048 -L xen_rescue -F "$DST" >/dev/null 2>&1
    DST_MNT="$DST".mnt
    mkdir -p "$DST_MNT"
    mount -o loop "$DST" "$DST_MNT"
    if [ $? -ne 0 ]; then
        error "Failed to mount destination disk image via loopback."
    fi
    echo "Copying files from '$SRC'..."
    if test -d "$SRC"; then
        if [ ! -d "$SRC"/dev ] || [ ! -d "$SRC"/sbin ]; then
            error "'$SRC' does not look like a valid root filesystem."
        fi
        cp_rescue "$SRC" "$DST_MNT"
        if [ $? -ne 0 ]; then
            cp_error
        fi
    else
        mkdir -p "$DST".src
        if test ! -z "`file $SRC | grep gzip`"; then
            cp -p "$SRC" "$DST".stage.gz
            gunzip -f "$DST".stage.gz || rm -f "$DST".stage.gz
            mount -o loop "$DST".stage "$DST".src
            if [ $? -ne 0 ]; then
                rm "$DST".stage
                rmdir "$DST".src
                error "Failed to mount the source via loopback."
            fi
            cp_rescue "$DST".src "$DST_MNT"
            if [ $? -ne 0 ]; then
                umount "$DST".src
                rm "$DST".stage
                rmdir "$DST".src
                cp_error
            fi
            umount "$DST".src
            rm "$DST".stage
        else
            mount -o loop "$SRC" "$DST".src
            if [ $? -ne 0 ]; then
                rmdir "$DST".src
                error "Failed to mount the source via loopback."
            fi
            cp_rescue "$DST".src "$DST_MNT"
            if [ $? -ne 0 ]; then
                umount "$DST".src
                rmdir "$DST".src
                cp_error
            fi
            umount "$DST".src
        fi
        rmdir "$DST".src
    fi
}

# Save some inodes
remove_some_files()
{
    # these consume an excessive amount of inodes
    rm -f "$DST_MNT"/dev/sd[c-z][a-z][0-9]*
    # hwclock does not work
    rm -f "$DST_MNT"/etc/init.d/boot.d/*boot.clock
}

xenify_image()
{
    # Xen doesn't yet support virtualizing USB
    sed -i "s/^usbfs/#usbfs/" "$DST_MNT"/etc/fstab
}

# Copy extra files to rescue image
copy_extra_files()
{
    test ! -e "$DST_MNT"/sbin/depmod && cp -p /sbin/depmod "$DST_MNT"/sbin/
    cp -p /usr/share/doc/packages/xen/boot.local.xenU "$DST_MNT"/etc/init.d/boot.local
}

# Remove kernel modules and replace by ours
exchange_kernel_modules()
{
    echo "Updating kernel within '$DST'..."
    KMODDIR=/lib/modules/$KVER/kernel
    MNTKVER="`cd "$DST_MNT"/lib/modules && ls -td */kernel 2>/dev/null | sed 's@/kernel@@' 2>/dev/null`"
    for dir in $MNTKVER; do 
        if test "$MNTKVER" != "$KVER"; then
            rm -rf "$DST_MNT"/lib/modules/$MNTKVER
        fi
    done    
    mkdir -p "$DST_MNT"$KMODDIR
    # complete trees
    for dir in arch crypto lib net security; do
        cp -ax $KMODDIR/$dir "$DST_MNT"$KMODDIR/
    done
    mkdir -p "$DST_MNT"$KMODDIR/fs
    cp -p $KMODDIR/fs/*.ko "$DST_MNT"$KMODDIR/fs/
    # a selection of FS
    for fs in afs autofs autofs4 cifs exportfs ext3 fat jbd jfs msdos ncpfs nfsd nls ntfs reiser4 reiserfs smbfs subfs sysv udf ufs vfat xfs; do
        if test -e $KMODDIR/fs/$fs; then
            cp -ax $KMODDIR/fs/$fs "$DST_MNT"$KMODDIR/fs/
        fi
    done
    # some drivers
    mkdir -p "$DST_MNT"$KMODDIR/drivers/char
    for name in lp.ko n_hdlc.ko raw.ko; do
        cp -p $KMODDIR/drivers/char/$name "$DST_MNT"$KMODDIR/drivers/char/
    done
    mkdir -p "$DST_MNT"$KMODDIR/drivers/block
    for name in umem.ko nbd.ko loop.ko loop_fish2.ko cryptoloop.ko; do
        cp -p $KMODDIR/drivers/block/$name "$DST_MNT"$KMODDIR/drivers/block/
    done
    mkdir -p "$DST_MNT"$KMODDIR/drivers/base
    cp -p $KMODDIR/drivers/base/firmware_class.ko "$DST_MNT"$KMODDIR/drivers/base/
    mkdir -p "$DST_MNT"$KMODDIR/drivers/md
    cp -p $KMODDIR/drivers/md/*.ko "$DST_MNT"$KMODDIR/drivers/md/
    mkdir -p "$DST_MNT"$KMODDIR/drivers/xen
    for dir in $KMODDIR/drivers/xen/*front; do
        cp -ax $dir "$DST_MNT"$KMODDIR/drivers/xen/
    done
    if test -e $KMODDIR/kernel; then
        mkdir -p "$DST_MNT"$KMODDIR/kernel
        cp -ax $KMODDIR/kernel/* "$DST_MNT"$KMODDIR/kernel/
    fi
    # Kernel image + System.map
    mkdir -p "$DST_MNT"/boot
    rm -f "$DST_MNT"/boot/vmlinuz-* "$DST_MNT"/boot/System.map-* "$DST_MNT"/boot/initrd-*
    cp -p /boot/vmlinuz-$KVER "$DST_MNT"/boot/
    if test -e /boot/initrd-$KVER-domU; then
        cp -p /boot/initrd-$KVER-domU "$DST_MNT"/boot/initrd-$KVER
    else
        cp -p /boot/initrd-$KVER "$DST_MNT"/boot/
    fi
    cp -p /boot/System.map-$KVER "$DST_MNT"/boot/
    depmod -a $KVER -b "$DST_MNT" -F "$DST_MNT"/boot/System.map-$KVER
    
}

# umount and display message
umount_and_msg()
{
    umount "$DST_MNT"
    rmdir "$DST_MNT"
    DST_MNT=
    echo "'$DST' has been prepared successfully."
    CFGFILE=/etc/xen/vm/${DST##*/}
    if test -e $CFGFILE; then
        mv -b $CFGFILE $CFGFILE.save
    fi
    if test "${DST:0:1}" != "/"; then
        DST="`pwd`/$DST"
    fi
    cp -p /etc/xen/examples/xmexample.rescue $CFGFILE
    sed -i "/^disk/s@^.*\$@disk = [ \'file:$DST,hda1,w\' ]@" $CFGFILE
    # These next two lines are only applicable if not using domUloader,
    # but try anyway.
    sed -i "/^kernel/s@^.*\$@kernel = \"/boot/vmlinuz-$KVER\"@" $CFGFILE
    sed -i "/^ramdisk/s@^.*\$@ramdisk = \"/boot/initrd-$KVER\"@" $CFGFILE
    echo ""
    echo "Config file '$CFGFILE' has been created.  Please review!"
    echo "You may also want to add an IP address to the config file."
    echo "Start the domain with 'xm create -c $CFGFILE'."
}

if test -z "$1" -o -z "$2"; then
    usage
fi
SRC=$1
if [ ! -e "$SRC" ]; then
    usage_error "'$SRC' does not exist."
fi
DST=$2
if [ -e "$DST" ]; then
    error "'$DST' already exists."
fi
MB=$MB_DEFAULT
[ ! -z "$3" ] && MB=$3
KVER=$4
if [ `id -u` -ne 0 ]; then
    usage_error "Please run this script as root."
fi

get_xen_kernel
create_basis_and_mount
remove_some_files
copy_extra_files
xenify_image
exchange_kernel_modules
umount_and_msg