Navigating the Filesystem

 This section looks at the file organization of Fedora 2 in general, based on the various utilities that are available and the location of configuration files. The root filesystem is indicated by the /. The contents of the root filesystem follow:   $ ls -F /   bin/   dev/  home/    lib/         misc/  opt/   root/  tftpboot/  usr/ boot/  etc/  initrd/  lost+found/  mnt/   proc/  sbin/  tmp/       var/ 

The utility programs are organized under the /bin , /usr/bin , and /usr/local/bin directories. The following tables list some of the common programs under these directories. It is very useful to ensure that these directories are set in the PATH environment variable.

Note

Remember, you can get full information on each of these by querying their man pages, and abridged details by typing the command followed by “ “ help .

Let s look at each of these directories in some detail.

The table that follows lists commands that are located in the /bin directory.

Command	Description
awk	Pattern-scanning and processing language
bash	The Bourne-again shell
cat	Concatenates files and prints on to standard output
chgrp	Changes the group ownership
chmod	Changes file access permissions
chown	Changes file ownership permissions
cp	Copies files and directories
cpio	Copies files to and from archives
csh	C-shell
cut	Removes sections from each line of input
date	Prints the current date and timestamp; super user may set the date and time
dd	Converts and copies files
Df	Displays disk usage for filesystems
dmesg	Displays startup messages
echo	Displays a line of text
ed	An old text editor
grep	Regular expression-matching program
gzip	GNU Zip program for compressing files
kill	Terminates running processes
Ln	Creates links to files and directories
Ls	Lists files
mail	Command line mail client
mkdir	Command line mail client
more	Paginates a file
mount	Maps a filesystem to a directory
mv	Moves a file from one location to another; same as renaming a file
netstat	Prints network statistics
ping	Checks for the network reachability of other machines on the network
ps	Lists currently running processes
pwd	Displays current working directory
rm	Removes files
rmdir	Removes directories
sed	Stream editor can be used to programmatically modify files and the output of programs
sh	Bourne shell
sleep	Delays for a specific amount of time
sort	Sorts the lines of input
su	Changes identity of a user
tar	Archiving program
tcsh	Enhanced C shell
touch	Updates the timestamp on a file
umount	Unmounts a currently mounted filesystem
uname	Prints system information
vi	A text editor

The commands in the following table are located in the /usr/bin directory.

Command	Description
At	Queues jobs for later execution
Bc	A bench calculator
Cc	C-compiler (this command is a symbolic link to the GNU C-compiler gcc)
Clear	Clears the screen
Crontab	Maintains a list of tasks to be performed later
Du	Reports disk usage for a directory and subdirectories
Emacs	An editor
F77	Fortran compiler
File	Prints file type
Find	File-searching utility
Finger	Looks up user information
ftp	File transfer program
Gcc	GNU C-compiler
Gdb	GNU debugger
Gftp	Graphical FTP client
Gimp	GNU image manipulation and painting program
Gmake	Maintains a group of programs (this command is a symbolic link to the GNU make command gmake )
Head	Displays the first few lines of a file
Ispell	Interactive spell checker
Lpr	Spools print jobs
Man	Displays manual pages for commands
Nslookup	Looks up a host s DNS information
Passwd	Changes a user s password
telnet	Telnet client allows remote logins
Wall	Sends a message to the terminals of all users currently logged on
Wc	Counts words, lines, and characters of input text
Which	Displays the full path of commands
Who	Displays the list of users currently logged on to the system

The next batch of files are system configuration files located in the /etc directory and its subdirectories. The following table contains some of the more commonly modified ones.

File	Description
Exports	Lists the filesystems to be exported via NFS
Ftpaccess	Configuration file for ftpd
Group	Lists the various groups on the system and each of their members
Hosts	Lists the hostname and IP addresses of machines
host.conf	Used by the DNS resolver library
Motd	Contains the message of the day
passwd	Contains user information for all users on the system
shadow	Contains the encrypted passwords of the user
xinetd.conf	Configuration file for the xinetd daemon

You can find administrative binaries under /sbin and /usr/sbin. The following table provides a list of commands from the /sbin directory.

Binary	Description
Arp	Prints a machine s Address Resolution Protocol (ARP) table
cardmgr	PCMCIA device manager
chkconfig	Manages runlevel information for system services
debugfs	Ext2 filesystem debugging utility
dhclient	DHCP client
e2fsck	Ext filesystem diagnosis and repair tool
fdisk	Disk-partitioning utility
fuser	Displays the IDs of processes using the specified files
ifconfig	Configures network interfaces
insmod	Installs loadable kernel modules
lspci	Lists all PCI devices on this systems
lspnp	Lists all PNP devices on this system
mkfs	Creates a new filesystem on a partition
modprobe	Detects and manages loadable modules
route	Displays and sets system routing table
sysctl	Displays or changes system parameters

The following table lists some of the files from the /usr/sbin directory.

Binary	Description
adduser	Creates a new user
automount	Configures mount points for autofs
chpasswd	Updates password file in batch mode
chroot	Runs command with the root set to a new root
gpm	Mouse-based cut and paste utility for virtual consoles
groupadd	Adds a new group
in.fingerd	Finger daemon
in.ftpd	FTP daemon
in.identd	identd daemon
in.telnetd	Telnet daemon
kudzu	Configures new hardware
pppd	PPP daemon
squid	HTTP caching server
tcpdump	TCP/IP diagnostics tool
vipw	Password file editor
zdump	Dumps time zone information

The /usr/local/bin directory usually houses new programs when they are installed.

Shared libraries (that is, libraries that contain common functions used by multiple programs at the same time without multiple in-memory copies) reside in the /lib , /usr/lib , and /usr/local/lib directories. It is often a good idea to ensure that the LD_LIBRARY_PATH environment variable contains these directories. This variable is not set by default, although it can be set in the .bashrc file or other startup files.

The /boot directory contains bootable images of Linux kernels . Following is an extract from a typical listing (here, the vmlinuz entries are the kernel binaries):

   $ ls /boot   boot.b chain.b config-2.4.18-14 config-2.4.18-17.8.0 ... vmlinuz-2.4.18-14 vmlinuz-2.4.18-17.8.0 

Transient and temporary files can be found under /var/tmp and /tmp . The /tmp directory is cleaned up by startup scripts after every reboot, whereas the /var/tmp directory is not. This behavior may dictate for some programmers the choice of using /var/tmp as opposed to /tmp .

Files related to peripherals, such as devices, can be found under the /dev directory. By convention, various peripherals, such as CD-ROM drives and floppy drives , are mounted under the /mnt directory. You ll see more on this directory in a later section.

The /proc directory provides a filesystem abstraction to the processes currently running on the system. Each process has a directory assigned to it and several files under it that contain information about the process. For more details, you should refer to the proc manual page by invoking the command man proc .

And, finally, as you first discovered in Chapter 2, the user s home directories are typically created under /home .