View source for MacOS/Resize HFS Plus disk

{{DISPLAYTITLE:Expand old JHFS+ disk on the command line}}

For a test I partitioned an external 500GB disk with a 157.3GB JHFS+ partition and the remaining 342.8GB with an Linux ext2. The whole thing was meant as backup disk. After some cleanup I was able to move all the data from the ext2 partition off somewhere else.
Eventually I wanted to make resize the JHFS+ partition to use all the 500GB. I thought that would be fairly simple. But I was totally wrong and had to really work hard to make it work. The description here is how I eventually got it working navigating around all the issues along the way. 

== Task ==
Repartion an disk that was created on an older version of MacOS X to use 100% of the disk space. Important the data on the volume must stay intact. 

== Tools ==
* diskutil (MacOS X)
* parted (Linux)

== Howto ==
There were a few issues along the way that had to be addressed one by one. Each is described in a subsection sequentially. 

=== Starting point ===
Starting out on the Mac <tt>diskutil list</tt> showed the following output.

Note: The disk is using an MBR or in Mac-speak FDisk_partition. 

 # diskutil list
 /dev/disk1
    #:                       TYPE NAME                    SIZE       IDENTIFIER
    <span class="highlight">0:     FDisk_partition_scheme                        *500.1 GB   disk1</span>
    1:                  Apple_HFS backup                  157.3 GB   disk1s1
    2:                  Apple_HFS disk1s2                 342.8 GB   disk1s2

=== Wrong partition scheme ===
Being fairly unfamiliar with the Mac tools I found <tt>diskutil</tt> has a number of great tools such as <tt>mergePartitions</tt> or <tt>resizeVolume</tt> unfortunately running them resulted in an rather non descriptive error. 

 # <span class="input">diskutil mergePartitions JHFS+ backup disk1s1 disk1s2</span>
 Merging partitions into a new partition
      Start partition: disk1s1 backup
      Finish partition: disk1s2 disk1s2
 
 <span class="highlight">Merging partitions encountered error 
   "MediaKit reports partition (map) too small  (-5341)".</span>
 The erase will not occur.

I was under the impression that the max partition size for <tt>MBR</tt> was 2TB but maybe it is different on the Mac so I wanted to convert it to <tt>GPT</tt>. And the almighty Internet could not clear thing up for me. In hindsight I was wrong all along and could have saved me some time but to that later. 

Trying to resize the volume was not much better. The <tt>R</tt> is to use all the available space.  

 # <span class="input">diskutil resizeVolume /Volumes/backup R</span>
 <span class="highlight">Error obtaining resizing information for grow to maximum</span>

At this point I decided to convert the whole disk to <tt>GPT</tt>. However doing so will destroy all data unless after the disk has been relabeled the exact same partition is put back in place. When it comes to partitioning making mistakes can send all the data south. As such I did it with the tool and OS im most familiar, parted on Linux had to do the repartitioning. 

=== Recreate the partition table under GPT in Linux ===

<div style="border: dotted 5px red; background: #f99; padding: 0.5em 0.5em;">
Note: Before starting copy the partition table of the disk to a text file so that it can recovery is possible should things turn pear shaped.

Any mistake in this process can destroy you data. Do not just copy and paste the example data here. If you are unsure and you don't have a backup of your data don't blame me.
</div>

To be ultra precise the <tt>unit</tt> of the display is set to Bytes. The <tt>print</tt> then shows the partition information prior to making any changes. 

 # <span class="input">parted /dev/sd<span class="highlight">X</span></span>
 (parted) <span class="input">unit B</span>
 (parted) <span class="input">print</span>
 Model: BUFFALO HD-PEU2 (scsi)
 Disk /dev/sdc: 500107862016B
 Sector size (logical/physical): 512B/512B
 Partition Table: msdos
 
 Number  Start          End            Size           Type     File system  Flags
  1      <span class="highlight">32256B         157283804159B</span>  157283771904B  primary  hfs+
  2      157283804160B  500105249279B  342821445120B  primary  hfs+         boot

With that information available the next step is to relabel the disk to <tt>GPT</tt>. 

 (parted) <span class="input">mklabel gpt</span>
 Warning: The existing disk label on /dev/sdc will be destroyed and all data on
 this disk will be lost. Do you want to continue?
 Yes/No? <span class="input">y</span>

At this point the disk has lost the previous partition table. In the next step we put it back exactly at the same boundaries as they were before. As the second partion is no longer used only the one holding the data is recreated.

 (parted) <span class="input">mkpart</span>
 Partition name?  []? <span class="input">Apple_HFS</span>
 File system type?  [ext2]? <span class="input">HFS</span>
 Start? <span class="input">32256B</span>
 End? <span class="input">157283804159B</span>
 Warning: The resulting partition is not properly aligned for best performance.
 Ignore/Cancel? <span class="input">i</span>
 (parted) <span class="input">quit</span>

With that connecting the disk back at the Mac.

=== Resizing with the GPT partition scheme ===

Back on the Mac <tt>diskutil list</tt> shows that the new partition scheme is in place and the data is miraculously still around.

 # <span class="input">diskutil list</span>
 /dev/disk1
    #:                       TYPE NAME                    SIZE       IDENTIFIER
    <span class="highlight">0:      GUID_partition_scheme                        *500.1 GB   disk1</span>
    1:                  Apple_HFS backup                  157.3 GB   disk1s1

Now with another <tt>resizeVolume</tt> attempt things look a lot better. This command takes a long time to go through all the checks so be patient. 

Note: I was using <tt>100%</tt> first which is not working at all. One must use <tt>R</tt> instead or it will bomb. 

 # <span class="input">diskutil resizeVolume disk1s1 R</span>
 Started partitioning on disk1s1 backup
 Verifying the disk
 Checking file system
 Checking Journaled HFS Plus volume
 Checking extents overflow file
 Checking catalog file
 Checking multi-linked files
 Checking catalog hierarchy
 Checking extended attributes file
 Checking multi-linked directories
 Checking volume bitmap
 Checking volume information
 The volume backup appears to be OK
 Resizing
 Finished partitioning on disk1s1 backup
 /dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk1
   <span class="highlight">1:                  Apple_HFS backup                  500.0 GB   disk1s1</span>

Yeah!!

[[Category: MacOS]]