build-vm, tar2fs: unify kver handling

No need to deduce kernel version again,
just save it in a temporary file.

The main reason to change what worked is
that e2k kernel-image package has Linux bits
named as image-$kver and not vmlinuz-$kver;
the guessing logic taking all of this into
account resulted in non-aesthetic patch.

NB: there's a duplicating script within
    kernel feature; it wasn't easy to avoid
    this and it might differ when handling
    multiple kernels, I didn't think much
    about this now as vm images tend to ship
    with the sole one.

bin/tar2fs

@@ -205,8 +205,14 @@ fi
 echo "MODULES_PRELOAD += $INITRD_MODULES $ROOTFSTYPE" >> "$ROOTFS/etc/initrd.mk"
 echo "FEATURES += qemu" >> "$ROOTFS/etc/initrd.mk"
 
-KERNEL="$(readlink $ROOTFS/boot/vmlinuz | sed 's,vmlinuz-,,')"
-chroot "$ROOTFS" make-initrd -k "$KERNEL"
+# NB: don't stick BOOTFS here, it has slightly different semantics
+pushd $ROOTFS/boot
+if [ -s .origver ]; then
+	read KVER < .origver
+fi
+[ -n "$KVER" ] || fatal "unable to deduce kernel version"
+chroot "$ROOTFS" make-initrd -k "$KVER"
+rm -f .origver
 
 # ...target device too
 sed -i "s,$LOOPROOT,$ROOTDEV," "$ROOTFS/etc/fstab"

features.in/build-vm/image-scripts.d/07-kernel

@@ -9,5 +9,12 @@ kver="$(rpm -qa 'kernel-image*' \
         | cut -f 2 -d ' ' \
         | sed 's/kernel-image-//')"
 
-ln -s vmlinuz-$kver /boot/vmlinuz
-ln -s initrd-$kver.img /boot/initrd.img
+[ -n "$kver" ] || { echo "** unable to deduce kernel version" >&2; exit 1; }
+
+cd /boot
+echo "$kver" > .origver	# for tar2fs
+
+# NB: e2k kernel builds "image" instead of "vmlinuz"
+[ -f vmlinuz-$kver ] && ln -s vmlinuz-$kver vmlinuz ||:
+ln -s initrd-$kver.img initrd.img	# missing at this stage
+: