Support --uuid= with --create to choose your own UUID.

ChangeLog

@@ -27,6 +27,7 @@ Changes Prior to this release
 	of error message.
     -   Don't hold md device open for so long in --monitor mode - map_dev
 	can be slow and interferes with trying to stop the array.
+    -   Support --uuid= with --create to choose your own UUID.
 
 Changes Prior to 2.5.6 release
     -   Fix bug which meant "bitmap=xxx" in mdadm.conf was not handled

Create.c

@@ -34,7 +34,7 @@
 
 int Create(struct supertype *st, char *mddev, int mdfd,
 	   int chunk, int level, int layout, unsigned long long size, int raiddisks, int sparedisks,
-	   char *name, char *homehost,
+	   char *name, char *homehost, int *uuid,
 	   int subdevs, mddev_dev_t devlist,
 	   int runstop, int verbose, int force, int assume_clean,
 	   char *bitmap_file, int bitmap_chunk, int write_behind, int delay)
@@ -407,7 +407,7 @@ int Create(struct supertype *st, char *mddev, int mdfd,
 				name += 2;
 		}
 	}
-	if (!st->ss->init_super(st, &super, &array, size, name, homehost))
+	if (!st->ss->init_super(st, &super, &array, size, name, homehost, uuid))
 		return 1;
 
 	if (bitmap_file && vers < 9003) {

Kill.c

@@ -67,7 +67,7 @@ int Kill(char *dev, int force, int quiet)
 		mdu_array_info_t info;
 		info.major_version = -1; /* zero superblock */
 		free(super);
-		st->ss->init_super(st, &super, &info, 0, "", NULL);
+		st->ss->init_super(st, &super, &info, 0, "", NULL, NULL);
 		if (st->ss->store_super(st, fd, super)) {
 			if (!quiet)
 				fprintf(stderr, Name ": Could not zero superblock on %s\n",

mdadm.8

@@ -1259,6 +1259,16 @@ is being created, then the name
 .B home
 will be used.
 
+A new array will normally get a randomly assigned 128bit UUID which is
+very likely to be unique.  If you have a specific need, you can choose
+a UUID for the array by giving the
+.B --uuid=
+option.  Be warned that creating two arrays with the same UUID is a
+recipe for disaster.  Also, using
+.B --uuid=
+when creating a v0.90 array will silently override any
+.B --homehost=
+setting.
 '''If the
 '''.B --size
 '''option is given, it is not necessary to list any component-devices in this command.

mdadm.c

@@ -516,6 +516,7 @@ int main(int argc, char *argv[])
 			continue;
 
 			/* now for the Assemble options */
+		case O(CREATE,'u'): /* uuid of array */
 		case O(ASSEMBLE,'u'): /* uuid of array */
 			if (ident.uuid_set) {
 				fprintf(stderr, Name ": uuid cannot be set twice.  "
@@ -1136,6 +1137,7 @@ int main(int argc, char *argv[])
 
 		rv = Create(ss, devlist->devname, mdfd, chunk, level, layout, size<0 ? 0 : size,
 			    raiddisks, sparedisks, ident.name, homehost,
+			    ident.uuid_set ? ident.uuid : NULL,
 			    devs_found-1, devlist->next, runstop, verbose-quiet, force, assume_clean,
 			    bitmap_file, bitmap_chunk, write_behind, delay);
 		break;

mdadm.h

@@ -319,7 +319,7 @@ extern struct superswitch {
 	int (*update_super)(struct mdinfo *info, void *sbv, char *update,
 			    char *devname, int verbose,
 			    int uuid_set, char *homehost);
-	int (*init_super)(struct supertype *st, void **sbp, mdu_array_info_t *info, unsigned long long size, char *name, char *homehost);
+	int (*init_super)(struct supertype *st, void **sbp, mdu_array_info_t *info, unsigned long long size, char *name, char *homehost, int *uuid);
 	void (*add_to_super)(void *sbv, mdu_disk_info_t *dinfo);
 	int (*store_super)(struct supertype *st, int fd, void *sbv);
 	int (*write_init_super)(struct supertype *st, void *sbv, mdu_disk_info_t *dinfo, char *devname);
@@ -409,7 +409,7 @@ extern int Build(char *mddev, int mdfd, int chunk, int level, int layout,
 
 extern int Create(struct supertype *st, char *mddev, int mdfd,
 		  int chunk, int level, int layout, unsigned long long size, int raiddisks, int sparedisks,
-		  char *name, char *homehost,
+		  char *name, char *homehost, int *uuid,
 		  int subdevs, mddev_dev_t devlist,
 		  int runstop, int verbose, int force, int assume_clean,
 		  char *bitmap_file, int bitmap_chunk, int write_behind, int delay);

super0.c

@@ -505,11 +505,11 @@ static int update_super0(struct mdinfo *info, void *sbv, char *update,
 
 
 static int init_super0(struct supertype *st, void **sbp, mdu_array_info_t *info,
-		       unsigned long long size, char *ignored_name, char *homehost)
+		       unsigned long long size, char *ignored_name, char *homehost,
+		       int *uuid)
 {
 	mdp_super_t *sb = malloc(MD_SB_BYTES + sizeof(bitmap_super_t));
 	int spares;
-	int rfd;
 	memset(sb, 0, MD_SB_BYTES + sizeof(bitmap_super_t));
 
 	if (info->major_version == -1) {
@@ -525,14 +525,11 @@ static int init_super0(struct supertype *st, void **sbp, mdu_array_info_t *info,
 		return 0;
 	}
 
-	rfd = open("/dev/urandom", O_RDONLY);
 	sb->md_magic = MD_SB_MAGIC;
 	sb->major_version = 0;
 	sb->minor_version = 90;
 	sb->patch_version = 0;
 	sb->gvalid_words = 0; /* ignored */
-	if (rfd < 0 || read(rfd, &sb->set_uuid0, 4) != 4)
-		sb->set_uuid0 = random();
 	sb->ctime = time(0);
 	sb->level = info->level;
 	if (size != info->size)
@@ -542,13 +539,23 @@ static int init_super0(struct supertype *st, void **sbp, mdu_array_info_t *info,
 	sb->raid_disks = info->raid_disks;
 	sb->md_minor = info->md_minor;
 	sb->not_persistent = 0;
-	if (rfd < 0 || read(rfd, &sb->set_uuid1, 12) != 12) {
+	if (uuid) {
-		sb->set_uuid1 = random();
+		sb->set_uuid0 = uuid[0];
-		sb->set_uuid2 = random();
+		sb->set_uuid1 = uuid[1];
-		sb->set_uuid3 = random();
+		sb->set_uuid2 = uuid[2];
+		sb->set_uuid3 = uuid[3];
+	} else {
+		int rfd = open("/dev/urandom", O_RDONLY);
+		if (rfd < 0 || read(rfd, &sb->set_uuid0, 4) != 4)
+			sb->set_uuid0 = random();
+		if (rfd < 0 || read(rfd, &sb->set_uuid1, 12) != 12) {
+			sb->set_uuid1 = random();
+			sb->set_uuid2 = random();
+			sb->set_uuid3 = random();
+		}
+		if (rfd >= 0)
+			close(rfd);
 	}
-	if (rfd >= 0)
-		close(rfd);
 	if (homehost) {
 		char buf[20];
 		char *hash = sha1_buffer(homehost,

super1.c

@@ -600,7 +600,7 @@ static int update_super1(struct mdinfo *info, void *sbv, char *update,
 }
 
 static int init_super1(struct supertype *st, void **sbp, mdu_array_info_t *info,
-		       unsigned long long size, char *name, char *homehost)
+		       unsigned long long size, char *name, char *homehost, int *uuid)
 {
 	struct mdp_superblock_1 *sb = malloc(1024 + sizeof(bitmap_super_t) +
 					     sizeof(struct misc_dev_info));
@@ -627,14 +627,29 @@ static int init_super1(struct supertype *st, void **sbp, mdu_array_info_t *info,
 	sb->feature_map = 0;
 	sb->pad0 = 0;
 
-	if ((rfd = open("/dev/urandom", O_RDONLY)) < 0 ||
+	if (uuid) {
-	    read(rfd, sb->set_uuid, 16) != 16) {
+		if (super1.swapuuid) {
-		*(__u32*)(sb->set_uuid) = random();
+			unsigned char *ac = (unsigned char *)sb->set_uuid;
-		*(__u32*)(sb->set_uuid+4) = random();
+			unsigned char *bc = (unsigned char *)uuid;
-		*(__u32*)(sb->set_uuid+8) = random();
+			int i;
-		*(__u32*)(sb->set_uuid+12) = random();
+			for (i=0; i<16; i+= 4) {
+				ac[i+0] = bc[i+3];
+				ac[i+1] = bc[i+2];
+				ac[i+2] = bc[i+1];
+				ac[i+3] = bc[i+0];
+			}
+		} else
+			memcpy(sb->set_uuid, uuid, 16);
+	} else {
+		if ((rfd = open("/dev/urandom", O_RDONLY)) < 0 ||
+		    read(rfd, sb->set_uuid, 16) != 16) {
+			*(__u32*)(sb->set_uuid) = random();
+			*(__u32*)(sb->set_uuid+4) = random();
+			*(__u32*)(sb->set_uuid+8) = random();
+			*(__u32*)(sb->set_uuid+12) = random();
+		}
+		if (rfd >= 0) close(rfd);
 	}
-	if (rfd >= 0) close(rfd);
 
 	if (name == NULL || *name == 0) {
 		sprintf(defname, "%d", info->md_minor);