Compared to a PC, phones and tablets are fairly locked-down
devices. Jailbreaking, rooting, and unlocking are all ways of bypassing their
limitations, and doing things that manufacturers and carriers don’t want you to
do.
Some countries have laws that prevent you from doing these things with
the devices you paid for and legally own — we won’t get into those laws here
Jailbreaking
Jailbreaking is the process of removing the limitations put in
place by a device’s manufacturer. Jailbreaking is generally performed on Apple
iOS devices, such as the iPhone or iPad. Jailbreaking removes the restrictions
Apple puts in place, allowing you to install third-party software from outside
the app store. Some people may have the perception that jailbreaking is only
used for piracy, but this isn not the case — jailbreaking allows you to do
things like change your iPhone’s default browser and mail client. Essentially,
jailbreaking allows you to use software that Apple doesn’t approve.
Jailbreaking can be performed on other devices with similar
limitations. For example, there is now a Microsoft Surface RT jailbreak that
allows you to install unapproved desktop programs. (By default, Windows RT systems only allow you to
run desktop applications written by Microsoft.) However, the desktop apps must
be compiled for ARM, so you can’t run any Windows desktop programs you already
have, although open-source applications could be tweaked and recompiled for the
Windows desktop on ARM.
Companies like Apple and Microsoft don’t want you jailbreaking
to get past a device’s limitations — so you can change the default programs on
iOS or run third-party desktop applications on Windows RT. To perform a
jailbreak, someone has to find a security vulnerability that allows them to
“exploit” the device and get around the manufacturer safeguards.
Android allows users to install third-party applications from
outside Google’s app store out-of-the-box and doesn’t need to be jailbroken.
Rooting
Rooting is the process of gaining “root access” to a device.
This is generally performed on Android devices, but rooting can also occur on
other devices based on Linux, such as Nokia’s now-retired Symbian operating
system.
On Linux and other UNIX-like operating systems, the root user is
essentially the same as the Administrator user on Windows. After rooting, you
can grant specific applications access to root permissions, allowing them to do
almost anything they want to the operating system. For example, an application
with root permissions could uninstall system applications, install low-level
system binaries, revoke permissions installed apps require, and do other crazy
things. Almost anything you can do on a proper Linux system, you can do with
root access on your phone.
Rooting gets around Android’s security architecture and could
potentially cause problems if users don’t know what they’re doing, so Android doesn’t come rooted.
On some devices, rooting may need to be accomplished via a security
exploit. Just like jailbreaking, manufacturers generally don’t want you
rooting. On some devices, such as Nexus devices (which are also intended for
developers), rooting does not require a security vulnerability.
Unlocking a Bootloader
Android is an open-source operating system, so anyone can take
the Android source code and create their own version of it. This allows custom
ROMs like Cyanogenmod to exist. Lots of custom ROMs exist for Android —
everything from large projects that support a variety of devices to custom ROMs
with a few theme patches some kid whipped up in his spare time.
However, many Android phones come with locked bootloaders. A
locked bootloader won’t boot anything but the manufacturer-approved version of
Android that comes with the device. Unlocking the bootloader allows you to
install custom ROMs — alternate versions of the Android operating system.
This isn’t just useful to geeks — Cyanogenmod brings new versions of Android to devices that
manufacturers no longer update. It’s a more vanilla Android experience, too —
many people like it because it is an alternative to the manufacturer-customized
user interfaces most Android devices come with.
Unlocking a device’s bootloader may also require a security
exploit, although companies like HTC and Motorola allow unlocking some devices. Nexus
devices (which are also intended for developers) can be easily unlocked.
Unlocking a boot loader can theoretically allow you to install
non-Android operating systems, too. For example, you can install Ubuntu for
phones or WebOS on a Galaxy Nexus with an unlocked bootloader. The desktop
version of Ubuntu can be installed on the Nexus 7, too. Of course, the
operating system must be built to be compatible with a specific device. These
operating systems probably aren’t particularly stable — but developers can use
the devices to run an alternate operating system while they work on it.
Unlocking a Phone
Many phones, particularly phones that come subsidized with a
contract, come “locked” to a specific carrier. The phone is set up so that it
can only be used on that carrier’s network. If you insert a SIM card from a
competing carrier into the phone, you will see a message indicating that the
phone is locked and cannot be used with the SIM card.
Unlocking a phone allows you to use it with a different SIM card
— either to use a different carrier while travelling or to take your current
phone with you while switching to a new service provider.
You will generally need an unlock code to unlock the phone. Many
carriers will unlock phones once your contract is up, while phones bought
outright without a contract may not be locked to a carrier at all. There are
ways to unlock phones without a carrier’s permission, too.
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