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Unit 10: File System

These include system administration as well as maintenance and hardware configuration notes
programs. Find lilo, fdisk, init, ifconfig etc. here. These are the essential programs that are
required by all the users. Another directory that contains system binaries is /usr/sbin.
This directory contains other binaries of use to the system administrator. This is where you
will find the network daemons for your system along with other binaries that only the system
administrator has access to, but which are not required for system maintenance, repair etc.
/bin - In contrast to /sbin, the bin directory contains several useful commands that are used by
both the system administrator as well as non-privileged users. This directory usually contains the
shells like bash, csh etc. as well as much used commands like cp, mv, rm, cat, ls.
There also is /usr/bin, which contains other user binaries. These binaries on the other hand are
not essential for the user. The binaries in /bin however, a user cannot do without.
/boot - This directory contains the system.map file as well as the Linux kernel. LILO places the
boot sector backups in this directory.
/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.
/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.

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