Mac recovery partion: revisited

Update (Oct 23, 2010): readers posted a lot of valuable comments to this article. Make sure you read them at the bottom of this page.
Some time ago I wrote an article about recreating a Lion recovery partition. The way described in hat article was very technical, complicated and risky.
While any way of adjusting partitions is risky, I found a safer way to recreate recovery partition after my Mac crashed again (looks like its life time is coming to an end). Here is how I did it the second time.

Install Lion

Install Lion on the USB drive or USB stick. If you use stick, make sure you got a good one. I got a very cheap one from Disk2Go and it took 4 hours to install Lion instead of normal 29 minutes.
Reboot to your main installation after installing.

Find partition information

Firsts, change to the root user:

Applico:~$ su -
 Password:
Applico:~#

List all your disks:

Applico:~# diskutil list
 /dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *128.0 GB   disk0
   1:                        EFI                         209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            127.7 GB   disk0s2
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *32.3 GB    disk1
   1:                        EFI                         209.7 MB   disk1s1
   2:                  Apple_HFS OSX                     31.4 GB    disk1s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3

From here we know that we have two disks: a hard disk (disk0) and a USB disk (disk1).
Get the information on the Macintosh HD and Recovery HD partitions:

 Applico~:# diskutil info /dev/disk0s2
    Device Identifier:        disk0s2
    Device Node:              /dev/disk0s2
    Part of Whole:            disk0
    Device / Media Name:      Macintosh HD
 
    Volume Name:              Macintosh HD
    Escaped with Unicode:     Macintosh%FF%FE%20HD
 
    Mounted:                  Yes
    Mount Point:              /
    Escaped with Unicode:     /
 
    File System Personality:  Journaled HFS+
    Type (Bundle):            hfs
    Name (User Visible):      Mac OS Extended (Journaled)
    Journal:                  Journal size 16384 KB at offset 0x3ba000
    Owners:                   Enabled
 
    Partition Type:           Apple_HFS
    OS Can Be Installed:      Yes
    Media Type:               Generic
    Protocol:                 SATA
    SMART Status:             Verified
    Volume UUID:              5C784582-B984-3B4A-85FE-245E9056CD5F
 
    Total Size:               127.7 GB (127691702272 Bytes) (exactly 249397856 512-Byte-Blocks)
    Volume Free Space:        28.2 GB (28211933184 Bytes) (exactly 55101432 512-Byte-Blocks)
    Device Block Size:        512 Bytes
 
    Read-Only Media:          No
    Read-Only Volume:         No
    Ejectable:                No
 
    Whole:                    No
    Internal:                 Yes
    Solid State:              Yes
 
 
 Applico:~# diskutil info /dev/disk1s3
    Device Identifier:        disk1s3
    Device Node:              /dev/disk1s3
    Part of Whole:            disk1
    Device / Media Name:      Recovery HD
 
    Volume Name:              Recovery HD
    Escaped with Unicode:     Recovery%FF%FE%20HD
 
    Mounted:                  No
 
    File System Personality:  Journaled HFS+
    Type (Bundle):            hfs
    Name (User Visible):      Mac OS Extended (Journaled)
    Journal:                  Unknown (not mounted)
    Owners:                   Disabled
 
    Partition Type:           Apple_Boot
    OS Can Be Installed:      No
    Media Type:               Generic
    Protocol:                 USB
    SMART Status:             Not Supported
    Volume UUID:              69F1FA77-EB09-3D79-BBD7-6101644A108B
 
    Total Size:               650.0 MB (650002432 Bytes) (exactly 1269536 512-Byte-Blocks)
    Volume Free Space:        0 B (0 Bytes) (exactly 0 512-Byte-Blocks)
    Device Block Size:        512 Bytes
 
    Read-Only Media:          No
    Read-Only Volume:         Not applicable (not mounted)
    Ejectable:                Yes
 
    Whole:                    No
    Internal:                 No
 
 

You need to note total sizes of both partitions.

Resize your main partition

Now we are going to resize our main partition. For that we calculate its new total size. To be safe I decied to substract 700 megabytes instead of 650. So the desired size is calculated like 127691702272-700*1024*1024=127040651264.
While we resize, we can also create a new partition:

Applico:~# diskutil resizeVolume /dev/disk0s2 127040651264B  jhfs+ "Recovery HD" 650002432B
Started partitioning on disk0s2 Macintosh HD
Verifying the disk
Checking file system
Performing live verification
Checking Journaled HFS Plus volume
Checking extents overflow file
Checking catalog file
Checking multi-linked files
Checking catalog hierarchy
Checking extended attributes file
Checking volume bitmap
Checking volume information
The volume Macintosh HD appears to be OK
Resizing
Waiting for the disks to reappear
Formatting disk0s3 as Mac OS Extended (Journaled) with name Recovery HD
Initialized /dev/rdisk0s3 as a 621 MB HFS Plus volume with a 8192k journal
Mounting disk
Finished partitioning on disk0s2 Macintosh HD
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *128.0 GB   disk0
   1:                        EFI                         209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            127.0 GB   disk0s2
   3:                  Apple_HFS Recovery HD             651.1 MB   disk0s3

Note that recovery partition size is not right. When adding partitions, diskutil made it larger than we asked. Fix it:

Applico:~# diskutil resizeVolume disk0s3 650002432B
 Started partitioning on disk0s3 Recovery HD
 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 volume bitmap
 Checking volume information
 The volume Recovery HD appears to be OK
 Resizing
 Finished partitioning on disk0s3 Recovery HD
 /dev/disk0
    #:                       TYPE NAME                    SIZE       IDENTIFIER
    0:      GUID_partition_scheme                        *128.0 GB   disk0
    1:                        EFI                         209.7 MB   disk0s1
    2:                  Apple_HFS Macintosh HD            127.0 GB   disk0s2
    3:                  Apple_HFS Recovery HD             650.0 MB   disk0s3
 

This step is important. If you do not get the right size, you are going to screw your recovery partition.

Copy recovery partition content

Now copy recovery partition content:

Applico:~# dd if=/dev/disk1s3 of=/dev/disk0s3
    1269536+0 records in
    1269536+0 records out
    650002432 bytes transferred in 185.538679 secs (3503326 bytes/sec)
 

Make sure you use regular disks (/dev/diskX), not raw disks (/dev/rdiskX). Raw disks always results in kernel panic in my case. Be careful with of argument. If you override a wrong place, you are screwed up. Double check where you copy!

Adjust partition type

That was the most risky part in the previous article. Now I found the easier way to do it:

Applico:~# asr adjust --target /dev/disk0s3 -settype "Apple_Boot"
    Fsck /dev/disk0s3 ....10....20....30....40....50....60....70....80....90....100
  Adjust completed successfully

Check it:

Applico:~ root# diskutil list
 /dev/disk0
    #:                       TYPE NAME                    SIZE       IDENTIFIER
    0:      GUID_partition_scheme                        *128.0 GB   disk0
    1:                        EFI                         209.7 MB   disk0s1
    2:                  Apple_HFS Macintosh HD            127.0 GB   disk0s2
    3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
 /dev/disk1
    #:                       TYPE NAME                    SIZE       IDENTIFIER
    0:      GUID_partition_scheme                        *32.3 GB    disk1
    1:                        EFI                         209.7 MB   disk1s1
    2:                  Apple_HFS OSX                     31.4 GB    disk1s2
    3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3
 

Everything seems to be in order.

Recheck your start up disk

Using diskutil may remove startup disk mark from your main disk. Go to the System Preferences (click Apple logo for that) and select “Startup Disk” item. Make sure that your Mac's hard drive is listed as startup disk.

Test recovery partition

Now you can reboot and hold Alt/Option key. The recovery partition should be appear as a boot option. You should be able to boot with it.

Conclusion

This way is much easier than the way I described before but it also took me some time to figure out all commands. The summary you see here should be error free. But if you find some errors or have anything to add, let me know and I will happily update the article.
When performing these steps, you must remeber that you do it on your own risk. Neither Apple, nor I will be able to help you if you screw it up. If unsure, ask somebody more accomplished or simply reinstall Lion normally.