Common Linux commands on system info

pwd 

Print working directory, i.e., display the name of my current directory on the screen.

hostname 

Print the name of the local host (the machine on which you are working). Use netconf (as root) to change the name of the machine.

whoami 

Print my login name.

id username 

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

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

who 

Determine the users logged on the machine.

rwho -a 

(=remote who) Determine all users logged on your network. The rwho service must be enabled for this command to run. If it isn't, run setup as root to enable "rwho".

finger user_name 

System info about a user. Try: finger root

last 

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

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.

uptime 

Show the amount of time since the last reboot.

ps 

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

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.

top 

Keep listing the currently running processes, sorted by cpu usage (top users first). In KDE, you can get GUI-based Ktop from "K"menu under "System"-"Task Manager" (or by executing "ktop" in an X-terminal).

uname -a 

(= Unix name with option "all") Info on your (local) server. I can also use guname (in X-window terminal) to display the info more nicely.

free 

Memory info (in kilobytes).

df -h 

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

du / -bh | more 

(=disk usage) Print detailed disk usage for each subdirectory starting at the "/" (root) directory (in human legible form).

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.

cat /proc/interrupts 

List the interrupts in use.

cat /proc/version 

Linux version and other info

cat /proc/filesystems 

Show the types of filesystems currently in use.

cat /etc/printcap 

Show the setup of printers.

lsmod 

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

set|more 

Show the current user environment.

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.

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.