The problem this patch is trying to address is libguestfs behavior on the
appliance startup. It starts supporting to use root=UUID definition in
the kernel command line of its root filesystem using
file -- /usr/lib64/guestfs/appliance/root
This works fine with RAW image, but we are using QCOW2 as a storage to
save a bit of file space and in this case we get
QEMU QCOW Image (v3), 1610612736 bytes
instead of UUID of the root filesystem.
The solution is very simple - we should dump first 256k of the image file
like the follows
qemu-io -c "read -V 0 256k" appliance | file -
which will provide correct result for all possible types of the appliance
storage.
Unfortunately, additional option for qemu-io is the only and the simplest
solution as '-v' creates very specific output, which requires to be
parsed. 'qemu-img dd of=/dev/stdout' does not work and the fix would be
much more intrusive.
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com>
CC: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
CC: Kevin Wolf <kw...@redhat.com>
CC: Max Reitz <mre...@redhat.com>
CC: Richard W.M. Jones <rjo...@redhat.com>
---
P.S. Patch to libguestfs will follow.
qemu-io-cmds.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index baeae86d8c..7aae9726cd 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -718,7 +718,7 @@ static const cmdinfo_t read_cmd = {
.cfunc = read_f,
.argmin = 2,
.argmax = -1,
- .args = "[-abCqv] [-P pattern [-s off] [-l len]] off len",
+ .args = "[-abCqvV] [-P pattern [-s off] [-l len]] off len",
.oneline = "reads a number of bytes at a specified offset",
.help = read_help,
};
@@ -728,6 +728,7 @@ static int read_f(BlockBackend *blk, int argc, char **argv)
struct timespec t1, t2;
bool Cflag = false, qflag = false, vflag = false;
bool Pflag = false, sflag = false, lflag = false, bflag = false;
+ bool vrawflag = true;
int c, cnt, ret;
char *buf;
int64_t offset;
@@ -737,7 +738,7 @@ static int read_f(BlockBackend *blk, int argc, char **argv)
int pattern = 0;
int64_t pattern_offset = 0, pattern_count = 0;
- while ((c = getopt(argc, argv, "bCl:pP:qs:v")) != -1) {
+ while ((c = getopt(argc, argv, "bCl:pP:qs:vV")) != -1) {
switch (c) {
case 'b':
bflag = true;
@@ -777,6 +778,9 @@ static int read_f(BlockBackend *blk, int argc, char **argv)
case 'v':
vflag = true;
break;
+ case 'V':
+ vrawflag = true;
+ break;
default:
qemuio_command_usage(&read_cmd);
return -EINVAL;
@@ -869,10 +873,15 @@ static int read_f(BlockBackend *blk, int argc, char
**argv)
if (vflag) {
dump_buffer(buf, offset, count);
}
+ if (vrawflag) {
+ write(STDOUT_FILENO, buf, count);
+ }
/* Finally, report back -- -C gives a parsable format */
- t2 = tsub(t2, t1);
- print_report("read", &t2, offset, count, total, cnt, Cflag);
+ if (!vrawflag) {
+ t2 = tsub(t2, t1);
+ print_report("read", &t2, offset, count, total, cnt, Cflag);
+ }
out:
qemu_io_free(buf);
--
2.17.1
