In late January an international group of iOS experts have released the first tool for untethered jailbreaking of Apple mobile devices that use the A5 dual-core processor (iPod 2 and iPhone 4S), designed by Apple and built by Samsung. For those of you new to the topic, jailbreaking is a term used to describe a form of privilege escalation. When you buy your iPhone, the operating system treats you as a user, limiting the range of modifications your can do to the system. Jailbreaking allows you to raise your access to root (administrator) level. Untethered jailbreak (as opposed to a tethered jailbreak) allows you to reboot your mobile device without having to connect it to the computer.

An iPhone 4S is a fairly sophisticated computer capable of doing many interesting things. Unfortunately, since most phone users are computer idiots, to preserve its bottom line and the sanity of its tech support staff, Apple imposes severe limitations on what you, as a user, can do with your iPhone or iPad. As a Unix sysadmin I am entirely on Apple’s side on this one. However, it would have been nice if Apple allowed an option of full access in exchange for voluntarily giving up warranty rights: for those of us who know what they are doing and are not gonna run in tears to the nearest Genius Bar if something goes wrong.

It’s always a good idea not to use the latest and greatest version of anything – especially software. And so I waited for a couple of weeks since the release of the jailbreaking tool before using it on my iPhone. It was a good idea to wait: during this time the jailbreaking application was updated four times. I decided to write up a brief overview of the process and the overall experience of using Absinthe – the jailbreaking tool.

I have the iPhone 4S running iOS 5.0.1. connected to my Toshiba Qosmio laptop running 64-bit Windows 7 via the standard sync cable that came with the phone. I downloaded the Absinthe version 0.4 for Windows. It is a single executable file – no installation required.

Four very import things to keep in mind:

1. Make sure you do a full backup of your iPhone. Make sure the backup completed without problems. This is absolutely crucial.

2. Jailbreaking voids the warranty. If something doesn’t work and you take your phone to Apple, the guys at the Genius Bar will instantly know what you tried to do and will tell you to take a hike.

3. The backup and jailbreaking process can take hours. Do not begin unless you are certain you are not going to need your phone during this time. This is best done overnight on a weekend.

4. Jailbreaking is not necessary. You will void the warranty and risk destroying your data for no good reason. I don’t encourage you jailbreaking your iPhone. I did this because: a) I was curious; b) I am a computer expert; and c) I have money for a new iPhone. If you are not in even one of these three categories, forget jailbreaking and go play Angry Birds instead.

The process was as follows:

1. Download Absinthe, extract the zip file to the desktop. Run in once without connecting the iPhone, just to make sure it works. Exit the application. Read the included “readme” file. It’s important and contains up-to-date information about using the software.

2. Launch iTunes, make sure its updated to the current version. Run a full backup of your iPhone. Make damn sure the backup completes successfully! That’s your only lifeline in case the jailbreaking effort fails.

Before starting the jailbreaking process, keep this in mind: your computer needs to stay up during the several hours this process will take. If you are using a laptop, make sure it’s plugged in. If you are using a desktop, it would be a good idea to have it connected to a UPS. Just in case there is a power spike or a brief outage. While the Absinthe instructions do not mention this, it is also a good idea to reboot your iPhone or iPad prior to jailbreaking.

Absinthe is known to have problems handling very large files on your iPhone. If you’ve been taking videos in 1080p resolution, you probably have some 500Mb+ files in your camera roll. The problem here seems to be not the overall amount of data, but the size of individual files. I do not know the maximum file size that Absinthe can handle. However, it is also possible that the problem is caused by limited remaining disk space on the iPhone. Whatever the case may be, before jailbreaking, I would suggest connecting your iPhone to a computer, and moving these large files over. Or, perhaps, even moving all of your photos and videos off the iPhone. This will reduce the chance of Absinthe getting stuck.

Another suggestion I’ve seen online (but did not need to try and so cannot recommend) is to: a) do a full backup of your iPhone (including all the apps, ringtones, contacts, music, etc); b) restore the factory default image (no large files there); c) run the jailbreak; d) run sync to put your apps, contacts, etc. back on the phone. I would imagine this can get quite involved. Hopefully, if you wait a little bit more, there might be a new Absinthe version without such a restrictive file size limitation.

If you do decide to reset the phone to factory image before jailbreaking, you can find instructions here. The basic process is:

a) Do a full backup of your phone;

b) Reset the phone and erase all data;

c) Follow the initial setup steps to configure your phone as new;

d) Apply the jailbreak;

e) Install Cydia;

f) Restore your latest backup.

Note: The question that commonly comes up is how to restore from the latest backup. iTunes, being garbage software that it is, does not make this obvious. Open iTunes, connect your phone and, once it appears in the list of devices, right-click on it and select option to restore from backup. Now, it is important to make sure that you select the correct backup: pay attention to the time stamp on the backup. It may not be the latest backup available, but the one prior to last.

3. Exit iTunes and launch Absinthe. Connect the iPhone (if iTunes launches automatically, kill it). Absinthe will detect your iPhone. Click the “Jailbreak” button.

4. At this point you need to be very patient. One of the things the jailbreaking process does is restructure the filesystem on your iPhone. These devices can have many gigabytes of disk space and data, so this restructuring process will take a while. Go watch TV or something, because Absinthe will be stuck at the following screen for quite some time: Beginning jailbreak, this may take a while…

Don’t panic. Yet. If this screen remains unchanged for, say, half-an-hour or longer, disconnect the iPhone. Go to the “Photos” and you may notice that all of your photos and videos are gone. If that is the case, Absinthe might have chocked on some big file in your camera roll. Restart Absinthe and re-connect your iPhone. Absinthe will detect it and say that you already tried to jailbreak but something went wrong. It will attempt to automatically fix the problem. This should be a relatively quick process, since no data was actually removed from the device.

Now disconnect the iPhone and check the “Photos” again – all of your stuff should be back where you left it. At this point you need to seriously consider connecting your phone to a PC and moving all your photos and videos off the iPhone to get rid of giant video files and free up some space. Then you can try jailbreaking again and, hopefully, this time around things will go smoother.

If your jailbreaking effort gets stuck at this screen for an unreasonable amount of time, removing large video files from your iPhone’s Photos album may help.

ss