System Information Commands

System Information Commands

Basic commands used by intermediate users from the command line. Many of these tools can be accomplished graphically, this document is aimed at augmenting GUI tools such as gnome-system-monitor.

information
This is by no means a full list of commands or switches.
Users requiring a list of switches or further explanation of command should consult the man pages.
There is a wealth of knowledge on how to use and what commands do can be obtained from www.google.com/linux
Some commands will need to be performed by root, type su - which will give you root status.

System Command	Example(s)	Details
whoami	whoami	Prints the user name associated with the current effective user ID
who	who	Print information about users who are currently logged in
id	id	print real and effective user and group IDs
last	last	shows previously logged in users
date	date 123123572000	sets or views the date
time	time	times a function on a system.
history	history	provides a history of command line commands issues by users.
uptime	uptime	shows uptime of the system.
ps	ps	Reports a snapshot of the current processes.
top	top	displays Linux tasks in a realtime text menu tool
uname	uname -a	Print certain system kernel information etc.
free	free	Prints free memory in system
df	df -h	Prints the disk partitions and available spave
du	du -h	Prints the sizes of files and folders
proc info	cat /proc/	Gives raw proc information for resources
	cat /proc/cpuinfo	Gives CPU count and details recognized by system
	cat /proc/interrupts	Gives interrupts used
	cat /proc/meminfo	Provides RAM memory details.
	cat /proc/version	Provides system information, kernel, etc.
lsmod	lsmod |more	list the loaded modules for devices etc. (i.e. is networking card driver loaded?)
PATH	echo $PATH	Gives folders in a path for a particular user.
dmesg	dmesg |more	Give detailed log messages.

System Commands

whoami

Print my login name.

[thesmartguy@wifitest]$ whoami
thesmartguy

who

Determine the users logged on the machine.

[root@wifitest]# who
thesmartguy pts/1 2007-11-19 09:34 (:0.0)

id

Print user id (uid) and his/her group id (gid), effective id (if different than the real id) and the supplementary groups.

[thesmartguy@wifitest]$ id thesmartguy
uid=500(thesmartguy) gid=501(thesmartguy) groups=501(thesmartguy)

back to top

last

Show listing of users last logged-in on your system.

[root@wifitest]# last
thesmart pts/1 :0.0     Mon Nov 19 09:34   still logged in   
thesmart :0             Mon Nov 19 09:33   still logged in   
reboot                  2.6.18-53.el5 Mon Nov 19 09:31   (00:31)

date

Print or change the operating system date and time. E.g., I could change the date and time to 2000-12-31 23:57 using this command:

date 123123572000

To set the hardware (BIOS) clock from the system (Linux) clock, use the command (as root) setclock

time

Determine the amount of time that it takes for a process to complete + other info. Don't confuse it with the date command. E.g. I can find out how long it takes to display a directory content using: time ls

[root@wifitest]# time ls
anaconda-ks.cfg cds install.log install.log.syslog jimmit  scsrun.log
real 0m0.007s
user 0m0.003s
sys  0m0.004s

history | more

Show the last (1000 or so) commands executed from the command line on the current account. The "| more" causes the display to stop after each screenful.

[root@wifitest]# history
     1  lpc
     2  lpc ?
     3  lpc ?
     4  lpc \-s
     5  lpc status
     6  ps axu
     7  man pid

uptime

Show the amount of time since the last reboot.

[root@wifitest]# uptime
10:05:45 up 34 min,  1 user,  load average: 1.01, 0.47, 0.48

ps

(=print status) List the processes currently run by the current user.

[thesmartguy@wifitest]$ ps
 PID TTY       TIME CMD
 20216 pts/1   00:00:00 bash
 20658 pts/1   00:00:00 ps

ps axu | more

List all the processes currently running, even those without the controlling terminal, together with the name of the user that owns each process.
(List to large for example.)

top

Keep listing the currently running processes, sorted by cpu usage (top users first).
List to large for example.

uname -a

(= Unix name with option "all") Info on your (local) server.

[root@wifitest]# uname -a
Linux wifitest.uk.ibm.com 2.6.18-53.el5 #1 SMP Wed Oct 10 16:34:02 EDT 2007 i686 i686 i386 GNU/Linux

uname -r

Kernel only reported.

[root@wifitest]# uname -r
2.6.18-53.el5

free

Memory info (in kilobytes).

[root@wifitest ]# free
    total      used       free     shared    buffers     cached
Mem: 1026108   1010252     15856       0       27768      485084

- + buffers/cache: 497400     528708
            Swap: 1052248     0    1052248

df -h

(=disk free) Print disk info about all the filesystems (in human-readable form)

[root@wifitest ]# df -h
Size  Used Avail Use% Mounted on
/dev/hda1      36G  4.5G   29G  14% /
tmpfs         502M     0  502M   0% /dev/shm

du / -bh | more

(=disk usage) Print detailed disk usage for each subdirectory starting at the "/" (root) directory (in human legible form).
Careful this will list all directory's under / (everything on machine)

cat /proc/cpuinfo

Cpu info - it show the content of the file cpuinfo. Note that the files in the /proc directory are not real files - they are hooks to look at information available to the kernel.

[root@wifitest]# cat /proc/cpuinfo
 processor     : 0
 vendor_id     : GenuineIntel
 cpu family    : 6
 model         : 13
 model name    : Intel(R) Pentium(R) M processor 1.40GHz
 stepping      : 6
 cpu MHz       : 600.000
 cache size    : 2048 KB
 bogomips      : 1196.52

cat /proc/interrupts

List the interrupts in use.

[root@wifitest ]# cat /proc/interrupts
0: 983295    IO-APIC-edge  timer
1:   1106    IO-APIC-edge  i8042
7:      1    IO-APIC-edge  parport0
8:      1    IO-APIC-edge  rtc
9:   2414    IO-APIC-level  acpi
12:  78970    IO-APIC-edge  i8042
14:  45698    IO-APIC-edge  ide0
15:  25704    IO-APIC-edge  ide1

cat /proc/meminfo

list the memory in a system

MemTotal:        2539180 kB
MemFree:          376988 kB
Buffers:           53488 kB
Cached:          1706536 kB

cat /proc/version

Linux version and other info

[root@wifitest]# cat /proc/version
Linux version 2.6.18-53.el5 (brewbuilder@hs20-bc2-3.build.redhat.com) (gcc version 4.1.2 20070626 (Red Hat 4.1.2-14)) #1 SMP Wed Oct 10 16:34:02 EDT 2007

cat /proc/filesystems

Show the types of filesystems currently in use.

[root@wifitest]# cat /proc/filesystems
     nodev sysfs
     nodev rootfs
     nodev proc
     nodev cpuset
     nodev securityfs
     nodev sockfs
     nodev usbfs
     nodev tmpfs
     nodev ext2
     nodev iso9660
     nodev ext3
     nodev autofs

lsmod

(As root. Use /sbin/lsmod to execute this command when you are a non-root user.) Show the kernel modules currently loaded.

[root@wifitest]# /sbin/lsmod
Module         Size  Used by
wlan_tkip      15872  2 
drm            65493  3 i915
lt_hotswap     14856  0 
tun       14657  1 
autofs4        24389  2 
hidp           23105  2 
rfcomm         42457  0 
l2cap          29633  10 hidp,rfcomm
bluetooth      53925  5 hidp,rfcomm,l2cap

(List continues to large for example.)

echo $PATH

Show the content of the environment variable "PATH". This command can be used to show other environment variables as well. Use "set" to see the full environment.

[root@wifitest]# echo $PATH
/usr/kerberos/sbin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/opt/ibm/c4eb/bin:/usr/kerberos/bin:/root/bin

dmesg | less

Print kernel messages (the content of the so-called kernel ring buffer). Press "q" to quit "less". Use less /var/log/dmesg to see what "dmesg" dumped into this file right after the last system bootup.

(List to large for Example.)