tinyramfs/generate

#!/bin/sh
#
# tiny initramfs generation tool

# debugging
set -x

# check root and files
if [ "$(id -u)" != 0 ]; then
    echo "must be run as root"
    exit 1
elif [ ! -e ./config ]; then
    echo "config doesn't exists"
    exit 1
elif [ ! -e ./init ]; then
    echo "init doesn't exists"
    exit 1
# TODO remove static busybox dependency | handle busybox requirements ( busybox --list | grep ash )
elif [ ! -n "$(ldd ./busybox | grep "not a dynamic executable")" ]; then
    echo "busybox doesn't exists or dynamically linked. please download or/and build static busybox"
    exit 1
fi

# source config
. ./config

# variables
tmpdir="$(mktemp -d /tmp/initramfs.XXXXXXXX)"
kernel="$(uname -r)"
moddir="/lib/modules"
binaries="./busybox findfs blkid mount modprobe umount $binaries"

# structure
for d in dev tmp var run etc usr/lib usr/bin mnt/root proc root sys; do
    mkdir -p "$tmpdir/$d"
done

# symlinks
( cd "$tmpdir" && {
    ln -s usr/lib lib
    ln -s usr/lib lib64
    ln -s usr/bin bin
    ln -s usr/bin sbin
    ln -s ../run var/run
    cd "$tmpdir/usr"
    ln -s bin sbin
    ln -s lib lib64
} )

# TODO parse fstab | crypttab
#while [ "$use_fstab" -eq 1 ] && read fs dir type opts; do thing; done < /etc/fstab

# handle device managers
if [ "$use_mdevd" = 1 ]; then
    # install mdevd
    binaries="mdevd mdevd-coldplug $binaries"
    mkdir "$tmpdir/lib/mdev"
    cp mdev.conf "$tmpdir/etc"
    cp storage-device "$tmpdir/lib/mdev"
    chmod +x "$tmpdir/lib/mdev/storage-device"
elif [ "$use_mdev" = 1 ]; then
    # install mdev
    mkdir "$tmpdir/lib/mdev"
    cp mdev.conf "$tmpdir/etc"
    cp storage-device "$tmpdir/lib/mdev"
    chmod +x "$tmpdir/lib/mdev/storage-device"
elif [ "$use_udev" = 1 ]; then
    # install udev
    binaries="udevd udevadm dmsetup $binaries"
    find /usr/lib/udev -type f | grep -v "rc_keymaps\|hwdb.d" | cpio -pd "$tmpdir"
fi

cat <<EOF > "$tmpdir/etc/group"
root:x:0:
tty:x:5:
dialout:x:11:
uucp:x:14:
kmem:x:3:
input:x:25:
video:x:13:
audio:x:12:
lp:x:10:
disk:x:9:
cdrom:x:16:
tape:x:6:
kvm:x:24:
floppy:x:8:
EOF

cat <<EOF > "$tmpdir/etc/passwd"
root:x:0:0::/root:/bin/sh
nobody:x:99:99::/:/bin/false
EOF

# handle lvm
if [ "$use_lvm" = 1 ] && [ -x "$(command -v lvm)" ]; then
    binaries="lvm $binaries"
    #mkdir "$tmpdir/etc/lvm"

    # use_lvmetad = 0 - avoid lvmetad missing warning message
    #cat <<EOF > "$tmpdir/etc/lvm/lvmlocal.conf"
    #local {
    #	issue_discards = ${lvm_discard:-0}
    #	use_lvmetad = 0
    #}
    #EOF
    # TODO implement use_lvmconf
fi

# handle luks
if [ "$use_luks" = 1 ] && [ -x "$(command -v cryptsetup)" ]; then
    binaries="cryptsetup $binaries"

    # avoid locking directory missing warning message
    mkdir "$tmpdir/run/cryptsetup"

    # TODO get rid of this workaround
    # workaround for luks2
    cp /usr/lib/libgcc_s.so.1 "$tmpdir/usr/lib"

    [ "$luks_discard" = 1 ] && luks_args="--allow-discards $luks_args"

    # TODO detached header
    # TODO keyfile
fi

# TODO rewrite drivers installing | handle $drivers config var
# install drivers
find \
    "$moddir/$kernel/kernel/drivers/virtio" \
    "$moddir/$kernel/kernel/arch" \
    "$moddir/$kernel/kernel/crypto" \
    "$moddir/$kernel/kernel/fs" \
    "$moddir/$kernel/kernel/lib" \
    "$moddir/$kernel/kernel/drivers/block" \
    "$moddir/$kernel/kernel/drivers/ata" \
    "$moddir/$kernel/kernel/drivers/md" \
    "$moddir/$kernel/kernel/drivers/scsi" \
    "$moddir/$kernel/kernel/drivers/usb/storage" \
    "$moddir/$kernel/kernel/drivers/usb/host" \
    -type f | cpio -pd "$tmpdir" 2>/dev/null

# install list of drivers
cp "$moddir/$kernel/modules.softdep" "$moddir/$kernel/modules.builtin" "$moddir/$kernel/modules.order" "$tmpdir/$moddir/$kernel"

# generate dependencies list of drivers
depmod -b "$tmpdir" "$kernel"

# TODO make strip optional
# install and strip binaries and libraries
for b in $(echo $binaries); do
    # check binary existence
    if [ ! "$(command -v $b)" ]; then
	echo "$b doesn't exists or permission denied"
	exit 1
    fi

    # copy and strip binary
    cp "$(command -v $b)" "$tmpdir/usr/bin"
    chmod +x "$tmpdir/usr/bin/$b"
    strip -s "$tmpdir/usr/bin/$b"

    # check statically linking
    ldd "$(command -v $b)" >/dev/null || continue

    # handle libraries symlinks for dymanically linked binaries
    for l in $(ldd "$(command -v $b)" | sed -nre 's,.* (/.*lib.*/.*.so.*) .*,\1,p' -e 's,.*(/lib.*/ld.*.so.*) .*,\1,p'); do
	# check symlink
	if [ -h "$l" ]; then
	    # check lib already existence
	    if [ ! -e "$tmpdir/usr/lib/${l##*/}" ] && [ ! -e "$tmpdir$(readlink -f $l)" ]; then
		# regular
		cp "$(readlink -f $l)" "$tmpdir/usr/lib"
		strip -s "$tmpdir$(readlink -f $l)"
		# TODO handle all symlinks
		# symlink may link to symlink
		[ -h "/usr/lib/$(readlink $l)" ] && cp -a "/usr/lib/$(readlink $l)" "$tmpdir/usr/lib"
		# symlink
		cp -a "$l" "$tmpdir/usr/lib"
	    fi
	else
	    if [ ! -e "$tmpdir/usr/lib/${l##*/}" ]; then
		cp "$l" "$tmpdir/usr/lib"
		strip -s "$tmpdir/usr/lib/${l##*/}"
	    fi
	fi
    done
done

# install init
cp ./init "$tmpdir/init"
chmod +x "$tmpdir/init"

# initialize config
cat <<EOF > "$tmpdir/config"
root="$root"
root_type="$root_type"
root_args="$root_args"
use_mdevd="$use_mdevd"
use_mdev="$use_mdev"
use_udev="$use_udev"
#drivers="$drivers"
use_lvm="$use_lvm"
use_luks="$use_luks"
luks_root="$luks_root"
luks_header="$luks_header"
luks_keyfile="$luks_keyfile"
luks_args="$luks_args"
EOF

# TODO add another compession tools
# packing
if ! ( cd "$tmpdir" && find . | cpio --create --verbose --format=newc | gzip --best ) > "./initramfs-$kernel.img.gz" 2>/dev/null; then
    echo "failed"
    exit 1
fi

# remove tmpdir
rm -rf "$tmpdir"

echo "done! check out initramfs-$kernel.img.gz"