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Wednesday 23 May 2012

interesting


/dev - This is a very interesting directory that highlights one important
characteristic of the Linux filesystem - everything is a file or a
directory. Look through this directory and you should see hda1, hda2 etc,
which represent the various partitions on the first master drive of the
system. /dev/cdrom and /dev/fd0 represent your CDROM drive and your floppy
drive. This may seem strange but it will make sense if you compare the
characteristics of files to that of your hardware. Both can be read from
and written to. Take /dev/dsp, for instance. This file represents your
speaker device. So any data written to this file will be re-directed to
your speaker. Try 'cat /etc/lilo.conf > /dev/dsp' and you should hear some
sound on the speaker. That's the sound of your lilo.conf file! Similarly,
sending data to and reading from /dev/ttyS0 ( COM 1 ) will allow you to
communicate with a device attached there - your modem.

/etc - This directory contains all the configuration files for your system.
Your lilo.conf file lies in this directory as does hosts, resolv.conf and
fstab. Under this directory will be X11 sub-directory which contains the
configuration files for X. More importantly, the /etc/rc.d directory
contains the system startup scripts. This is a good directory to backup
often. It will definitely save you a lot of re-configuration later if you
re-install or lose your current installation.

/home - Linux is a multi-user environment so each user is also assigned a
specific directory which is accessible only to them and the system
administrator. These are the user home directories, which can be found
under /home/username. This directory also contains the user specific
settings for programs like IRC, X etc.

/lib - This contains all the shared libraries that are required by system
programs. Windows equivalent to a shared library would be a DLL file.

/lost+found - Linux should always go through a proper shutdown. Sometimes
your system might crash or a power failure might take the machine down.
Either way, at the next boot, a lengthy filesystem check using fsck will
be done. Fsck will go through the system and try to recover any corrupt
files that it finds. The result of this recovery operation will be placed
in this directory. The files recovered are not likely to be complete or
make much sense but there always is a chance that something worthwhile is
recovered.

/mnt - This is a generic mount point under which you mount your filesystems
or devices. Mounting is the process by which you make a filesystem
available to the system. After mounting your files will be accessible
under the mount-point. This directory usually contains mount points or
sub-directories where you mount your floppy and your CD. You can also
create additional mount-points here if you want. There is no limitation to
creating a mount-point anywhere on your system but convention says that
you do not litter your file system with mount-points.

/opt - This directory contains all the software and add-on packages that
are not part of the default installation. Generally you will find KDE and
StarOffice here. Again, this directory is not used very often as it's
mostly a standard in Unix installations.

/proc - This is a special directory on your system. We have a more detailed
article on this one here.

/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.

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