sfdisk: add --disk-id to change disk UUID/ID

Addresses: https://github.com/karelzak/util-linux/issues/916
Signed-off-by: Karel Zak <kzak@redhat.com>

disk-utils/sfdisk.8

@@ -152,6 +152,11 @@ or a GUID for GPT.  For backward compatibility the options \fB\-c\fR and
 Change the GPT partition UUID.  If \fIuuid\fR is not specified,
 then print the current partition UUID.
 .TP
+.BR "\-\-disk\-id \fIdevice " [ \fIid ]
+Change the disk identifier.  If \fIid\fR is not specified,
+then print the current identifier.  The identifier is UUID for GPT
+or unsigned integer for MBR.
+.TP
 .BR \-r , " \-\-reorder " \fIdevice
 Renumber the partitions, ordering them by their start offset.
 .TP

disk-utils/sfdisk.c

@@ -86,6 +86,7 @@ enum {
 	ACT_PARTUUID,
 	ACT_PARTLABEL,
 	ACT_PARTATTRS,
+	ACT_DISKID,
 	ACT_DELETE
 };
 
@@ -1327,6 +1328,46 @@ static int command_partattrs(struct sfdisk *sf, int argc, char **argv)
 	return write_changes(sf);
 }
 
+/*
+ * sfdisk --disk-id <device> [<str>]
+ */
+static int command_diskid(struct sfdisk *sf, int argc, char **argv)
+{
+	const char *devname = NULL;
+	char *str = NULL;
+
+	if (!argc)
+		errx(EXIT_FAILURE, _("no disk device specified"));
+	devname = argv[0];
+
+	if (argc == 2)
+		str = argv[1];
+	else if (argc > 2)
+		errx(EXIT_FAILURE, _("unexpected arguments"));
+
+	if (fdisk_assign_device(sf->cxt, devname, !str) != 0)
+		err(EXIT_FAILURE, _("cannot open %s"), devname);
+
+	/* print */
+	if (!str) {
+		fdisk_get_disklabel_id(sf->cxt, &str);
+		if (str)
+			printf("%s\n", str);
+		free(str);
+		fdisk_deassign_device(sf->cxt, 1);
+		return 0;
+	}
+
+	/* change */
+	if (sf->backup)
+		backup_partition_table(sf, devname);
+
+	if (fdisk_set_disklabel_id_from_string(sf->cxt, str) != 0)
+		errx(EXIT_FAILURE, _("%s: failed to set disklabel ID"), devname);
+
+	return write_changes(sf);
+}
+
 static void sfdisk_print_partition(struct sfdisk *sf, size_t n)
 {
 	struct fdisk_partition *pa = NULL;
@@ -1941,6 +1982,9 @@ static void __attribute__((__noreturn__)) usage(void)
 	fputs(_(" --part-uuid <dev> <part> [<uuid>] print or change partition uuid\n"), out);
 	fputs(_(" --part-attrs <dev> <part> [<str>] print or change partition attributes\n"), out);
 
+	fputs(USAGE_SEPARATOR, out);
+	fputs(_(" --disk-id <dev> [<str>]           print or change disk label ID (UUID)\n"), out);
+
 	fputs(USAGE_SEPARATOR, out);
 	fputs(_(" <dev>                     device (usually disk) path\n"), out);
 	fputs(_(" <part>                    partition number\n"), out);
@@ -2007,6 +2051,7 @@ int main(int argc, char *argv[])
 		OPT_PARTLABEL,
 		OPT_PARTTYPE,
 		OPT_PARTATTRS,
+		OPT_DISKID,
 		OPT_BYTES,
 		OPT_COLOR,
 		OPT_MOVEDATA,
@@ -2052,6 +2097,8 @@ int main(int argc, char *argv[])
 		{ "part-type",  no_argument,    NULL, OPT_PARTTYPE },
 		{ "part-attrs", no_argument,    NULL, OPT_PARTATTRS },
 
+		{ "disk-id",    no_argument,	NULL, OPT_DISKID },
+
 		{ "show-pt-geometry", no_argument, NULL, 'G' },		/* deprecated */
 		{ "unit",    required_argument, NULL, 'u' },		/* deprecated */
 		{ "Linux",   no_argument,       NULL, 'L' },		/* deprecated */
@@ -2192,6 +2239,9 @@ int main(int argc, char *argv[])
 		case OPT_PARTATTRS:
 			sf->act = ACT_PARTATTRS;
 			break;
+		case OPT_DISKID:
+			sf->act = ACT_DISKID;
+			break;
 		case OPT_NOREREAD:
 			sf->noreread = 1;
 			break;
@@ -2296,6 +2346,10 @@ int main(int argc, char *argv[])
 		rc = command_partattrs(sf, argc - optind, argv + optind);
 		break;
 
+	case ACT_DISKID:
+		rc = command_diskid(sf, argc - optind, argv + optind);
+		break;
+
 	case ACT_REORDER:
 		rc = command_reorder(sf, argc - optind, argv + optind);
 		break;