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Network Operating Systems-I

notes /proc - This is a special directory on your system.
/root - We talked about user home directories earlier and well this one is the home directory of
the user root. This is not to be confused with the system root, which is directory at the highest
level in the filesystem.
/tmp - This directory contains mostly files that are required temporarily. Many programs use this
to create lock files and for temporary storage of data. On some systems, this directory is cleared
out at boot or at shutdown.

/usr - This is one of the most important directories in the system as it contains all the user binaries.
X and its supporting libraries can be found here. User programs like telnet, ftp etc. are also placed
here. /usr/doc contains useful system documentation. /usr/src/linux contains the source code
for the Linux kernel.
/var - This directory contains spooling data like mail and also the output from the printer daemon.
The system logs are also kept here in /var/log/messages. You will also find the database for
BIND in /var/named and for NIS in /var/yp.

Note The files recovered are not likely to be complete or make much sense but there
always is a chance that something worthwhile is recovered.

10.1.1 managing file systems

In Linux, as it is for Unix, the separate file systems the system may use are not accessed by device
identifiers (such as a drive number or a drive name) but instead they are combined into a single
hierarchical tree structure that represents the file system as one whole single entity. Linux adds
each new file system into this single file system tree as it is mounted.
All file systems, of whatever type, are mounted onto a directory and the files of the mounted file
system cover up the existing contents of that directory. This directory is known as the mount
directory or mount point. When the file system is unmounted, the mount directory’s own files
are once again revealed.
When disks are initialized (using fdisk, say) they have a partition structure imposed on them that
divides the physical disk into a number of logical partitions. Each partition may hold a single file
system, for example an EXT2 file system.
File systems organize files into logical hierarchical structures with directories, soft links and so
on held in blocks on physical devices. Devices that can contain file systems are known as block
devices. The IDE disk partition /dev/hda1, the first partition of the first IDE disk drive in the
system, is a block device.

The Linux file systems regard these block devices as simply linear collections of blocks, they
do not know or care about the underlying physical disk’s geometry. It is the task of each block
device driver to map a request to read a particular block of its device into terms meaningful to its
device; the particular track, sector and cylinder of its hard disk where the block is kept.

Task “File systems organize files into logical hierarchical structures with directories,
soft links and so on held in blocks on physical devices.” Comment

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