On Thu, Aug 13, 2020 at 07:48:52AM +0300, Andrey Shinkevich wrote:
For the appliance of the QCOW2 format, the function get_root_uuid()
fails to get the UUID of the disk image.
In this case, let us read the first 256k bytes of the disk image with
the 'qemu-img dd' command. Then pass the read block to the 'file'
command.
Suggested-by: Denis V. Lunev <den(a)openvz.org>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich(a)virtuozzo.com>
Thanks, I pushed this with a few minor adjustments to error
handling in the get_root_uuid function.
Rich.
v3:
01: The code refactoring was made based on reviewers comments.
The e-mail thread Message-Id:
<1597246570-901723-1-git-send-email-andrey.shinkevich(a)virtuozzo.com>
lib/appliance-kcmdline.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 67 insertions(+), 1 deletion(-)
diff --git a/lib/appliance-kcmdline.c b/lib/appliance-kcmdline.c
index fbeb4f4..e088fc0 100644
--- a/lib/appliance-kcmdline.c
+++ b/lib/appliance-kcmdline.c
@@ -71,7 +71,7 @@ read_uuid (guestfs_h *g, void *retv, const char *line, size_t len)
* The L<file(1)> command does the hard work.
*/
static char *
-get_root_uuid (guestfs_h *g, const char *appliance)
+get_root_uuid_with_file (guestfs_h *g, const char *appliance)
{
CLEANUP_CMD_CLOSE struct command *cmd = guestfs_int_new_command (g);
char *ret = NULL;
@@ -96,6 +96,72 @@ get_root_uuid (guestfs_h *g, const char *appliance)
}
/**
+ * Read the first 256k bytes of the in_file with L<qemu-img(1)> command
+ * and write them into the out_file. That may be useful to get UUID of
+ * the QCOW2 disk image with further L<file(1)> command.
+ * The function returns zero if successful, otherwise -1.
+ */
+static int
+run_qemu_img_dd (guestfs_h *g, const char *in_file, char *out_file)
+{
+ CLEANUP_CMD_CLOSE struct command *cmd = guestfs_int_new_command (g);
+ int r;
+
+ guestfs_int_cmd_add_arg (cmd, "qemu-img");
+ guestfs_int_cmd_add_arg (cmd, "dd");
+ guestfs_int_cmd_add_arg_format (cmd, "if=%s", in_file);
+ guestfs_int_cmd_add_arg_format (cmd, "of=%s", out_file);
+ guestfs_int_cmd_add_arg (cmd, "bs=256k");
+ guestfs_int_cmd_add_arg (cmd, "count=1");
+
+ r = guestfs_int_cmd_run (cmd);
+ if (r == -1) {
+ error (g, "Failed to run qemu-img");
+ return -1;
+ }
+ if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
+ guestfs_int_external_command_failed (g, r, "qemu-img dd", NULL);
+ return -1;
+ }
+
+ return 0;
+}
+
+/**
+ * Get the UUID from the appliance disk image.
+ */
+static char *
+get_root_uuid (guestfs_h *g, const char *appliance)
+{
+ char *uuid = NULL;
+ int ret;
+ CLEANUP_UNLINK_FREE char *tmpfile = NULL;
+
+ uuid = get_root_uuid_with_file (g, appliance);
+ if (uuid) {
+ return uuid;
+ }
+
+ tmpfile = guestfs_int_make_temp_path (g, "root", "raw");
+ if (!tmpfile) {
+ error (g, "get_root_uuid: failed to make temporary file");
+ return NULL;
+ }
+
+ ret = run_qemu_img_dd (g, appliance, tmpfile);
+ if (ret < 0) {
+ return NULL;
+ }
+
+ uuid = get_root_uuid_with_file (g, tmpfile);
+ if (!uuid) {
+ error (g, "Failed to get the appliance UUID");
+ }
+
+ return uuid;
+}
+
+/**
* Construct the Linux command line passed to the appliance. This is
* used by the C<direct> and C<libvirt> backends, and is simply
* located in this file because it's a convenient place for this
--
1.8.3.1
--
Richard Jones, Virtualization Group, Red Hat
http://people.redhat.com/~rjones
Read my programming and virtualization blog:
http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine. Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/