Tag Archives: diskutil

waiting for root device: could be duplicate UUIDs

Posted on by

If you run into waiting for root device when booting in verbose mode or you get a flashing question mark, etc, it could be that your volumes have duplicate UUIDs. The UUID is the primary means that is used to locate the boot volume to root from. If you have duplicate UUIDs, your Mac may not be able to determine which volume to boot from. If you suspect this may be the case, boot from another disk or CD and run diskutil list to get a list of all volumes. Then run diskutil info on each to get the UUIDs. Check for duplicates.

kserver:~ pbuffer$ diskutil list
/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *74.5 Gi disk0
1: EFI 200.0 Mi disk0s1
2: Apple_HFS int_1 19.8 Gi disk0s2
3: Apple_HFS int_2 19.8 Gi disk0s3
4: Apple_HFS int_3 34.5 Gi disk0s4

kserver:~ pbuffer $ diskutil info disk0s2 | grep UUID
Volume UUID: A1F5866F-8286-359A-B19F-58910918AC5A
kserver:~ pbuffer$ diskutil info disk0s3 | grep UUID
Volume UUID: A1F5866F-8286-359A-B19F-58910918AC5A
kserver:~ pbuffer $ diskutil info disk0s4 | grep UUID
Volume UUID: CBB0B1F8-07D5-3BFC-9B50-4F99033B01D6

If you do find a duplicate, you can generate a new UUID and set it using the following command:

unmount the disk first

diskutil unmountDisk disk0

/System/Library/Filesystems/hfs.fs/hfs.util -s disk0s2

substitute your own device for disk0s2

Once you’ve done this, re-bless the volume.

Duplicate UUIDs shouldn’t happen, but somehow it happened to one of our Xserves with a hardware raid card.

Bootable Software RAID 0+1, 1+0 in Mac OS X

Posted on by

Software RAID striped mirrors or mirrored stripes are possible in Mac OS X. They may be 10.5 only. I haven’t tested other versions.

Simply create your striped sets using DiskUtility or diskutil, then use the command line diskutil and supply the /dev/diskx entries of the stripe sets when creating your mirror.

First run diskutil list to get the /dev/disk entries for each stripe, then create your mirror using:

diskutil createRAID mirror MirrorName JHFS+ disk1 disk2

where disk1 is the device for the first stripe set and disk2 is the device for the second stripe set.

The result is also bootable and will display correctly as a nested RAID in DiskUtility.app.

convert lines to comma separated items with tr

Posted on by

If you have output that is separated by new lines, but you really want it formatted into a single line with commas as separators or maybe a space as a separator, just pipe to tr.

Here is a simple example:

kserver:~ patternbuffer$ diskutil list | grep ^/dev
/dev/disk0
/dev/disk1

If we want them separated by spaces, we could do:

kserver:~ patternbuffer$ diskutil list | grep ^/dev | tr '\n' ' '
/dev/disk0 /dev/disk1

Note that there is a newline on the end of the output, so that trailing newline is also translated. So if you don’t want it there, you’ll have to chomp it off. I use sed, but use what you like.

Here is the same as above, but with commas, with sed to remove the trailing comma.

kserver:~ patternbuffer$ diskutil list | grep ^/dev | tr '\n' ',' | sed 's/.$//'
/dev/disk0,/dev/disk1