From 8ff9cbe29970a9db2141d084b6db32b9323bf40e Mon Sep 17 00:00:00 2001 From: Peter Gerber Date: Tue, 3 Jul 2018 19:52:32 +0000 Subject: [PATCH] setup-rwdev.sh: Only check first 1 GiB for zeros As described in QubesOS/qubes-issues#3758, a VM may fail to start if the volume is large. This because the whole volume is read to ensure it's empty (=all zeros). This changes limits the check to the first 1 GiB of the private volume. As additional safety, a scan with blkid is done. Fixes https://github.com/QubesOS/qubes-issues/issues/3758 --- init/setup-rwdev.sh | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/init/setup-rwdev.sh b/init/setup-rwdev.sh index 3796be5..c5db69e 100755 --- a/init/setup-rwdev.sh +++ b/init/setup-rwdev.sh @@ -3,13 +3,17 @@ set -e dev=/dev/xvdb +max_size=1073741824 # check at most 1 GiB if [ -e "$dev" ] ; then # The private /dev/xvdb device is present. # check if private.img (xvdb) is empty - all zeros - private_size_512=$(blockdev --getsz "$dev") - if head -c $(( private_size_512 * 512 )) /dev/zero | diff "$dev" - >/dev/null; then + private_size=$(( $(blockdev --getsz "$dev") * 512)) + if [ $private_size -gt $max_size ]; then + private_size=$max_size + fi + if cmp --bytes $private_size "$dev" /dev/zero >/dev/null && { blkid -p "$dev" >/dev/null; [ $? -eq 2 ]; }; then # the device is empty, create filesystem echo "Virgin boot of the VM: creating private.img filesystem on $dev" >&2 if ! content=$(mkfs.ext4 -m 0 -q "$dev" 2>&1) ; then