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setup-rwdev.sh: Only check first 1 GiB for zeros

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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
This commit is contained in:
Peter Gerber 2018-07-03 19:52:32 +00:00
parent 7d783b3010
commit 8ff9cbe299
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GPG Key ID: 07C068AEE44683A1
1 changed files with 6 additions and 2 deletions
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8
init/setup-rwdev.sh
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@ -3,13 +3,17 @@
set -e set -e
dev=/dev/xvdb dev=/dev/xvdb
max_size=1073741824 # check at most 1 GiB
if [ -e "$dev" ] ; then if [ -e "$dev" ] ; then
# The private /dev/xvdb device is present. # The private /dev/xvdb device is present.
# check if private.img (xvdb) is empty - all zeros # check if private.img (xvdb) is empty - all zeros
private_size_512=$(blockdev --getsz "$dev") private_size=$(( $(blockdev --getsz "$dev") * 512))
if head -c $(( private_size_512 * 512 )) /dev/zero | diff "$dev" - >/dev/null; then 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 # the device is empty, create filesystem
echo "Virgin boot of the VM: creating private.img filesystem on $dev" >&2 echo "Virgin boot of the VM: creating private.img filesystem on $dev" >&2
if ! content=$(mkfs.ext4 -m 0 -q "$dev" 2>&1) ; then if ! content=$(mkfs.ext4 -m 0 -q "$dev" 2>&1) ; then