The key features to enforce
security in Unix system is chroot. Chroot is an operation that changes the
apparent root directory for the current running process and their children. A
program that is run in such a modified environment cannot access files and
commands outside that environmental directory tree. Suppose that in the system, it has a user named Michael so
Michael's home directory is /user/michael, chroot makes it so that / points to
/user/michael on the hard drive.
Therefore, michael can't access parts of the system that he shouldn't.
This security measures restricts Michael in what is called a chroot() jail.
The word jail has encompassed any metaphorical padded cell
or "jail" restricting access to certain directories and limits which programs
can be run.
On the iphone, the flash drive contains two partitions one
of which is used for operating system (OS) and application and the other is for
user data. About 300mb of total storage is reserved for OS and applications in
partition /dev/disk0s1 whereas the rest of storage is dedicated to user data
such movies pictures, and music in partition /dev/disk0s2.
As shipped, iphone consists of two major restrictions as follows:
- The user can’t write to the os partition
- The iphone won’t run any programs stored on the data partition
If you install an app store application, it can run because
it is stored on the os partition.
In order to remove the restrictions mentioned above, the
process of jailbreaking is needed to change the file /etc/fstab in an attempt to enable you to do tasks as follows:
- Make the os partition writable
- Enable execution of programs on the data partition
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