Appendix H. Important System Directories

Sysadmins and anyone else writing administrative scriptsshould be intimately familiar with the following systemdirectories.

• /bin

  Binaries (executables). Basic system programsand utilities (such as bash).

• /usr/bin

  [1]

  More system binaries.

• /usr/local/bin

  Miscellaneous binaries local to the particular machine.

• /sbin

  System binaries. Basic system administrative programsand utilities (such as fsck).

• /usr/sbin

  More system administrative programs and utilities.

• /etc

  Et cetera. Systemwide configurationscripts.

  Of particular interest are the/etc/fstab(filesystem table),/etc/mtab(mounted filesystem table), and the /etc/inittabfiles.

• /etc/rc.d

  Boot scripts, on Red Hat and derivative distributionsof Linux.

• /usr/share/doc

  Documentation for installed packages.

• /usr/man

  The systemwide manpages.

• /dev

  Device directory. Entries (but notmount points) for physical and virtual devices.See Chapter 27.

• /proc

  Process directory. Contains information and statisticsabout running processes and kernel parameters.See Chapter 27.

• /sys

  Systemwide device directory. Contains information andstatistics about device and device names. This is newlyadded to Linux with the 2.6.X kernels.

• /mnt

  Mount. Directory for mountinghard drive partitions, such as /mnt/dos, and physicaldevices. In newer Linux distros, the /mediadirectory has takenover as the preferred mount point for I/O devices.

• /media

  In newer Linux distros, the preferred mount point forI/O devices, such as CD ROMs or USB flash drives.

• /var

  Variable(changeable) systemfiles. This is a catchall "scratchpad"directory for data generated while a Linux/UNIX machineis running.

• /var/log

  Systemwide log files.

• /var/spool/mail

  User mail spool.

• /lib

  Systemwide library files.

• /usr/lib

  More systemwide library files.

• /tmp

  System temporary files.

• /boot

  System bootdirectory. The kernel,module links, system map, and boot manager reside here.

   

  Altering files in this directory may result in anunbootable system.

Notes

[1]

Some early UNIX systems had a fast, small-capacity fixeddisk (containing /,the root partition), and a second drive whichwas larger, but slower (containing /usrand otherpartitions). The most frequently used programs andutilities therefore resided on the small-but-fastdrive, in /bin,and the others on the slower drive, in /usr/bin.

This likewise accounts for the split between/sbinand/usr/sbin,/liband /usr/lib, etc.