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.