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"

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

# TODO usr/lib64 usr/sbin
# symlinks
for s in lib lib64 bin sbin; do
    case "$s" in
	lib*)
	    ( cd "$tmpdir" && ln -s "usr/lib" "$s" )
	;;
	*bin)
	    ( cd "$tmpdir" && ln -s "usr/bin" "$s" )
	;;
    esac
done

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

# 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 "$tmpdir/usr/lib/$(readlink $l)" ]; then
		# regular
		cp "$(readlink -f $l)" "$tmpdir/usr/lib"
		strip -s "$tmpdir/usr/lib/$(readlink $l)"
		# symlink
		cp -a "$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"
rootfstype="$rootfstype"
rootflags="$rootflags"
drivers="$drivers"
#use_lvm="$use_lvm"
#lvm_discard="$lvm_discard"
#use_luks="$use_luks"
#luks_header="$luks_header"
#luks_keyfile="$luks_keyfile"
#luks_discard="$luks_discard"
EOF

# 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"