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appliance: extract UUID from QCOW2 disk image

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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@openvz.org>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
This commit is contained in:
Andrey Shinkevich
2020-08-13 07:48:52 +03:00
committed by Richard W.M. Jones
parent 2469b4b790
commit 3cad943a85
1 changed files with 62 additions and 1 deletions
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63
lib/appliance-kcmdline.c
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@@ -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;
@@ -95,6 +95,67 @@ get_root_uuid (guestfs_h *g, const char *appliance)
return ret;
}
/**
* 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;
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)
return NULL;
if (run_qemu_img_dd (g, appliance, tmpfile) == -1)
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