Linux System Management

Environment env Show all environment variables. export Set the value of a variable so it is visible to all subprocesses that belong to the current shell. printenv Print all or part of environment. reset Restores runtime parameters for session to default values. set Shows how the environment is set up. This is a builtin bash command. Library management ldconfig Updates the necessary links for the run time link bindings. ldd Tells what libraries a given program needs to run. ltrace A library call tracer. trace Same as ltrace. Module and kernel management depmod Handle loadable modules automatically. Creates a makefile-like dependency file. dmesg Print or control the kernel ring buffer. This shows the last kernel startup messages. genksyms Generate symbol version information. insmod Install loadable kernel module. lsmod List currently installed kernel modules. modprobe Used to load a set of modules that are marked with a specified tag. rmmod Unload loadable modules.

Runtime level management

exit		Terminates the shell.
halt		Stop the system.
init		Process control initialization.
initscript		Script that executes inittab commands.
logout		Log the user off the system.
poweroff		Brings the system down.
reboot		Reboot the system.
runlevel		List the current and previous runlevel.
setsid		Run a program in a new session.
shutdown		If your system has many users, use the command "shutdown -h +time message", where time is the time in minutes until the system is halted, and message is a short explanation of why the system is shutting down. # shutdown -h +10 'We will install a new disk. System should be back on-line in three hours.'
telinit		By requesting run level 1 a system can be taken to single user mode.

System Configuration tools

ctrlaltdel		Set the function of the ctrl alt del combination.
isapnp		Configure ISA plug and play devices.
kbdconf		A Redhat Linux tool which configures the /etc/sysconfig/keyboard file which specifies the location of the keyboard map file. This is a GUI based tool.
kbdrate		Set the keyboard repeat rate and delay time.
kernelcfg		A Redhat GUI kernel configuration tool, Start X, then run it from a console session.
linuxconf		Redhat's GUI linux system configuration tool.
lspci		List all pci devices.
mesg		Control write access to your terminal.
mouseconfig		A Redhat Linux tool used to configure the /etc/sysconfig.mouse file. This is a GUI tool.
ndc		Script file used to restart, stop, start the DNS server.
Printtool		Redhat's GUI printer configuration tool.
quota		Display disk usage and limits.
quotacheck		Scan a filesystem for disk usages.
quotaoff		Turn file system quotas off.
quotaon		Turn file system quotas on.
samba		Script file used to stop, start, restart samba services when not run using inetd.
setpci		Configure pci devices.
setserial		Set/get serial port information.
setterm		Set terminal attributes.
setup		Set up devices and file systems.
stty		Used to configure and print the console devices.
swapon		Enable devices and files for paging and swapping.
swapoff		Disable devices and files for paging and swapping.
timeconfig		A Redhat Linux tool used to configure the /etc/sysconfig/clock file. This is a GUI tool used to set timezone and whether or not the clock is set to GMT time.
tset		Used to initialize terminals.

System Information                 

arch		Print machine architecture.
df		Shows disk free space.
du		Shows disk usage.
free		Display used and free memory on the system.
ipcrm		Provide information on ipc facilities.
ipcs		Same as ipcrm.
lsdev		Display information about installed hardware via files in the /proc directory.
lsof		List open files.
lspci		List PCI devices .
pnpdump		Lists ISA plug and play devices resource information.
procinfo		Display system status gathered from proc.
pstree		Display a tree of processes.
runlevel		Find the current and previous system runlevel.
strace		Trace ssytem calls and signals for a binary program.
stty		Change and print terminal line settings.
tload		Prints a graphic representation of the system load average.
tty		Print the filename of the terminal connected to standard input.
uname		Print system information, Prints Linux.
vmstat		Report virtual memory statistics.
xcpustate		Displays CPU states (idle, nice, system, kernel) statistics. Runs in X?

System Logging

klogd		Kernel log daemon which intercepts and logs Linux kernel messages.
logger		Make entries in the system log.
syslogd		Linux system logging utilities.
sysklogd		Linux system logging utilities.

System Security

System time

cal		Calendar.
clock		Used to change or get current time. The command "clock -–w" sets the hardware clock.
date		Print or set the system date and time.
hwclock		Set or read the hardware CMOS clock.
timed		Time server daemon to synchronize the host's time with other machines, normally invoked at boot time from the rc(8) file.
timedc		Timed control program.
tzset		Used to change the users private time zone by setting the TZ environment variable.
uptime		Reports how long the system has been running.
zdump		Prints the current time in each zonename named on the command line.
zic		Reads text from files named on the command line and creates time conversion files.

X Management and programs

SuperProbe		Probe video hardware.
Xconfigurator		The Redhat tool used during system setup to configure X.
xconsole		Displays messages usually sent to /dev/console.
xf86config		Older version of XF86Setup.
XF86Setup		A newer X configuration program with a GUI interface which modifies the "/etc/X11/XF86Config" configuration file.
xvidtune		This program will test video modes on the fly without modification to your X configuration. Read the usr/X11R6/lib/X11/doc/VideoModes.doc file before running this program.