iPhone 1.1.x Dual Boot / Jailbreak

Brought to you by NerveGas, planetbeing, ghost_000, dinopio, bgm, MuscleNerd and the combined iPhone-Elite and iPhone/iTouch Dev teams. Writeup by NerveGas.


The dev team has been using dual-booting to jailbreak the iPhone for several months now, however now that several more advanced techniques have been developed (many of which are still private), I thought it apropos to release this cool hack for those who would like to dual boot multiple versions of the iPhone software (or other OS's) from their handset. It's a neat little hack that I think might be useful for developers playing with 1.2.

I'll walk you through a sample jailbreak scenario with 1.1.4, using 1.1.1, to show you what I mean. To do this, you will carve out a new partition on the iPhone and install version 1.1.1 on it. You'll then upgrade the iPhone to v1.1.4, which will leave the new partition intact. You can then dual-boot the iPhone, allowing you to mount 1.1.4's partition using the 1.1.1 partition. Once mounted, you'll make some changes to the mount points and install OpenSSH.

Once you've got two versions of the OS functional, you can easily switch between them by changing your root-device. For example:

nvram boot-args=“rd=disk0s3 -v”


The following instructions, like all iPhone hacking, can in theory result in PERMANENT, IRREPARABLE DAMAGE to your iPhone. This information is provided WITH NO WARRANTIES. All liability is DISCLAIMED.


Step 1: Downgrade iTunes, if necessary

As of the time of this writing, iPHUC did not work with iTunes 7.6. I'm not sure if they've updated this or not, but for now I am assuming that your version of iPHUC iwll probably be same.

If this is still the case, you'll need version 7.5 or earlier. If necessary, back up your ~/Music/iTunes library and delete iTunes. On OS X, you can do that with:

# rm -rf /Applications/iTunes.app
# rm -rf /System/Library/PrivateFrameworks/MobileDevice.framework
# mv ~/Music/iTunes ~/Music/iTunes.7.6

Now download and install iTunes v7.5.

Step 2: Set up iPHUC

If you need iPHUC, grab it from the 1.1.2-Jailbreak archive here: http://conceitedsoftware.com/iphone/site/112jb.html

Unzip it, then unzip jailbreak.jar, and this should extract iPHUC.

NOTE: Many other versions of iPHUC are incompatible, we recommend using this version, unless you have a newer one.

Step 3: Downgrade (or Upgrade) iPhone software, if necessary

You must start from an already jail-broken version of iPhone software, either 1.1.1 or later. Version 1.0.x will not work here unless you have an iPhone from approximately week 45 or earlier. If you are running 1.1.4, you'll want to downgrade back to 1.1.1. See Erica Sadun's blog post on downgrading: http://www.tuaw.com/2008/01/16/downgrading-your-1-1-3-iphone-or-ipod-touch/

If you're running 1.0.x, you'll need to upgrade to 1.1.1 unless you own an “early” iPhone.

Once you're up and running on 1.1.1, use the *#307# hack to break into a Safari session and install AppSnapp from http://www.jailbreakme.com. This will activate your phone and place the installer on SpringBoard.

Some decent instructions are here: http://www.pantsland.com/2007/12/03/simple-iphone-112-upgrade-instructions-with-unlock/

Install the BSD subsystem and SSH using AppTapp to access 1.1.1.

Step 4: Install necessary tools from 1.1.1 ramdisk:

Grab the following files from the 1.1.1 or 1.0.2 ramdisk:


NOTE: Only the version of fdisk on the ramdisk appears to work on the iPhone. If you have the wrong version, fdisk will complain that it can't recognize the device.

Install the binaries from the ramdisk into /usr/sbin on your 1.1.1 device, using scp. Then make them executable:

# chmod 755 /usr/sbin/*

Step 5: Prepare the partition table

Here, we'll be resizing the /private/var partition and create a third partition, disk0s3. This will blow away /private/var, so the first thing you need to do is create a backup of it. Your resulting /private/var partition will be 300MB smaller in size. If you choose to, you may put things back later on - although there is some value in keeping your iPhone dual-bootable.

# tar -cf /private.tar --preserve /private/var   # (ignore the errors)

Now unmount it:

# umount -f /private/var

Next, run fdisk:

 # fdisk -e /dev/disk0

If you get an error with the command above, it's because you've invoked a version of fdisk other than the one that came on the ramdisk. If this is the case, use the full path to wherever you placed the ramdisk version of fdisk.

You'll edit partition 2 to decrease its size by the number of cyliners that s1 is + the delta size between s1 and s2 (usually 120 or 123). For iPhone, this is likely 153720 cylinders. Next, edit partition 3 to begin using the same spacing as partitions 1 and 2 (though this may not be necessary) and to be the same size as as partition 1 (153600 on iPhone, 76800 on iPod).

The final table will look something like:

    4GB iPhone:
Disk: /dev/disk0        geometry: 983/32/63 [1982464 sectors]
Sector size: 2048 bytes
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
 1: AF    0   1   1 - 1023 254  63 [        63 -     153600] HFS+
 2: AF 1023 254  63 - 1023 254  63 [    153663 -    1674861] HFS+
 3: AF 1023 254  63 - 1023 254  63 [   1828644 -     153600] HFS+
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused
    8GB iPhone:
Disk: /dev/disk0  geometry: 983/64/63 [3964928 sectors]
Sector size: 2048 bytes
Offset: 0    Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
 1: AF    0   1   1 - 1023 254  63 [        63 -     153600] HFS+
 2: AF 1023 254  63 - 1023 254  63 [    153663 -    3657665] HFS+
 3: AF 1023 254  63 - 1023 254  63 [   3811328 -     153600] HFS+
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
    16GB iPod Touch:
Disk: /dev/disk0        geometry: 983/64/63 [3964928 sectors]
Sector size: 4096 bytes
Offset: 0       Signature: 0xAA55
        Starting       Ending
#: id  cyl  hd sec -  cyl  hd sec [     start -       size]
1: AF    0   1   1 - 1023 254  63 [        63 -      76800] HFS+
2: AF 1023 254  63 - 1023 254  63 [     76863 -    3811059] HFS+
3: AF 1023 254  63 - 1023 254  63 [   3887922 -      77006] HFS+
4: 00    0   0   0 -    0   0   0 [         0 -          0] unused
  8GB iPod Touch:
Disk: /dev/disk0        geometry: 983/64/63 [3964928 sectors]
Sector size: 2048 bytes
Offset: 0       Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
 1: AF    0   1   1 - 1023 254  63 [        63 -     153600] HFS+
 2: AF 1023 254  63 - 1023 254  63 [    153720 -    3657465] HFS+
 3: AF 1023 254  63 - 1023 254  63 [   3811185 -     153600] HFS+
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused

Be sure not to touch partition 1, otherwise you'll blow away your OS.

Once you've got it looking right, tell fdisk to write the new partition table out. When it's finished, you'll need to sync from the command-line:

# sync; sync; sync;

Your third partition is now set up!

For some reason, disk0s2 gets moved to disk0s4 in /dev. You'll need to move it back:

# mv /dev/disk0s4 /dev/disk0s2
# mv /dev/rdisk0s4 /dev/rdisk0s2

Step 6: Restore /private/var

The partition change will have blown away /private/var, so you'll need to restore it back to normal. To do this, format it and then extract your tarball:

newfs_hfs /dev/disk0s2
mount -t hfs /dev/disk0s2 /private/var
cd /private/var
tar -xvf /private.tar
mv ./private/var/* /private/var && rm -rf ./private

Step 7: Duplicate the OS partition

Here, you'll duplicate the OS partition (disk0s1) onto your newly created partition (disk0s3). To avoid corruption, you'll first remount your root as read-only:

# mount -o ro /

Next, use dd to copy the raw disk over:

# dd if=/dev/rdisk0s1 of=/dev/rdisk0s3 bs=4096

This will take several minutes. Once finished, it's a good idea to run a fsck:

# fsck_hfs /dev/disk0s3

Now remount your root as read-write and mount the new partition:

# mount -o rw /
# mkdir /mnt
# mount -t hfs /dev/disk0s3 /mnt

Step 8: Prepare the new boot partition

Once you have the new boot partition mouned, you'll need to make some changes to it to boot.

1. First, edit /mnt/etc/fstab so that it mounts your root as /dev/disk0s3 instead of disk0s1.

2. Second, you'll need to make an ugly symlink hack. The Apple upgrade process checks for suspicious partitions by looking for the existence of /sbin/launchd. If it finds it, the upgrade will fail. Fortunately, the check mounts the partition in a subdirectory and doesn't chroot, so if we move sbin to 'mysbin', and then link /sbin → /mysbin, the check will fail (because mysbin will actually be in /mnt), but the link will work when the partition is mountd as root:

# cd /mnt
# mv sbin mysbin
# ln -s /mysbin sbin

NOTE: Make sure you link to /mysbin, not just mysbin

It's now safe to dismount /mnt

3. You'll also want to delete any Installer caches from /private/var:

# find /private/var -name Installer -exec rm -rf {} \;

Step 9: Boot from the new partition

Three primary nvram values are used when booting the iPhone:

  • auto-boot (true): Determines whether the iPhone should auto-boot or go into recovery mode
  • boot-partition (0): Identifies the partition number (zero-indexed) to boot
  • boot-args: (empty): Can be used to set the root device and verbose mode

Set these up so that the iPhone boots off of the new partition:

# nvram boot-partition=2
# nvram boot-args="rd=disk0s3 -v"
# nvram auto-boot=true
# sync
# reboot

To confirm that your iPhone is running off of the new partition, run 'mount'. This will print out your disk mounts. The root filesystem should be mounted on disk0s3, not disk0s1.

If for some reason the device doesn't boot properly, you can attempt booting with iPHUC:

# iphuc
  #: enterrecovery (if necessary)
  #: cmd setenv\ boot-args\ rd=disk0s3\ -v
  #: cmd setenv\ boot-partition\ 2
  #: cmd setenv\ auto-boot\ true
  #: cmd saveenv
  #: cmd fsboot

If for some reason you can't get the device to respond, try forcing it into recovery mode by holding home + power until you see the graphic telling you to “Connect to iTunes”.

Step 10: Upgrade to 1.1.4.

Upgrade back to 7.6

In OS X, Version 1.1.4 can only be successfully upgraded by 7.6. In Windows, iTunes 7.5 is adequate. Otherwise, you'll need to temporarily upgrade to iTunes 7.6.

Upgrade iTunes back, then click 'Check for Updates'. This will prompt you to download 1.1.4. Click 'Download Only'.

Once you've downloaded 1.1.4, use the 'Update' button (NOT “Restore”). This will update the OS partition only, without erasing all the work you've done.

If iTunes didn't report a numeric error, then congratulations! You now have an iPhone capable of booting multiple versions. You'll probably still see the “Connect to iTunes” graphic on your iPhone. That will be taken care of below.

Downgrade back to 7.5

It seems like a pain, but iPHUC doesn't work with 7.6 (yet). If you needed to upgrade to 7.6 above then now you'll need to downgrade back to 7.5 to finish.

Step 11: Use iPHUC to boot the 1.1.1 partition

Extract your 1.1.4 ipsw file. You'll see a kernel cache. Copy this to the iPhone using iPHUC:

# iphuc
    #: filecopytophone kernelcache.release.s5l8900xrb

Now issue the following iPHUC commands to boot. Be sure to escape spaces:

    #: cmd setenv\ boot-args\ "rd=disk0s3\ -v"
    #: cmd setenv auto-boot true
    #: cmd saveenv
    #: cmd bootx

Step 12: Mount the 1.1.4 partition, and set up shop

Once booted back into 1.1.1, you'll be able to mount the 1.1.4 partition:

# fsck_hfs /dev/disk0s1
# mkdir /mnt
# mount -t hfs /dev/disk0s1 /mnt

Be sure to fsck it first, as the iPhone won't let you mount it otherwise.

You're now set! You have full read-write access to 1.1.4 via /mnt. You can change the master.passwd file, install OpenSSH, and install any applications you want.

Be sure to also edit fstab to allow for a read-write root filesystem.

To set up MobileTerminal, you'll have to do a few things to accommodate its running with non-privileged permissions:

  1. Install the BSD_Base and BSD_Extras from http://iphone.natetrue.com
  2. Copy Terminal.app into /mnt/Applications
  3. mkdir -p /mnt/usr/local/arm-apple-darwin/
  4. ln -s /usr/lib /mnt/usr/local/arm-apple-darwin/lib
  5. cp -p /mnt/bin/bash /mnt/bin/sh
  6. chmod 4755 /mnt/usr/bin/login
  7. Edit /mnt/etc/master.passwd to put your own password in

When you're ready to boot back on 1.1.4, se nvram up:

# nvram boot-partition=0
# nvram boot-args=""
# nvram auto-boot=true
# sync
# reboot

That's it! You're now dual-bootable between both versions. You could easily apply this to v1.2 (if you have it) or other firmware.

Log file

On this page is the logfile of an actual dual-boot installation using the above steps.


Please visit this hackint0sh.org thread for discussion about this technique and how to use it.

s5l8900/dualboot.txt · Last modified: 2008/06/05 01:43 (external edit)
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