Linux system status commands and utilities

uptime

This command displays a one line summary showing...

Example: uptime
11:42pm up 18 days, 8:45, 1 user, load average: 0.00, 0.00, 0.00

• Current time (11.42pm)
• Number of days since last boot (up 18 days)
• Number of users logged in (1 user)
• System utilization for the last 1, 5 and 15 minute intervals (load average)

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who

This command will display...

• All users logged in
• tty device (line) they are using
• When they logged in
• Idle time
• Where they logged in from

Options:

• -i display idle time
• -H print column headings

Example: who -iH

USER	LINE	LOGIN-TIME	IDLE	FROM
roger	ttyp0	Jun 5 23:27	.	(omni)

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id

This command displays a one line summary for the current user listing...

• user name and number
• primary group and number
• other groups and numbers

  Example: id
  uid=1000(roger) gid=100(users) groups=100(users),16(dialout),40(game)

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free

This command displays statistics on memory usage. The values represent KB's.

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du

This command stands for disk usage and will print the size of the current directory and subdirectories in 1 KB sizes.

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df

This command displays information for each file system.

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env

This command lists all shell (environment) variables and their contents for the current user.

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ps

This command lists process status. There are many options for this command. Below are the two most common.

Example: ps u (process status for current user)

• PID = Unique Process ID
• SIZE = Virtual image size; size of text+data+stack
• RSS = Resident set size; kilobytes of program in memory
• TTY = Controlling tty
• STAT = Information about the status of the process
  • R = runnable
  • S = sleeping
  • D = uninterruptible sleep
  • T = stopped or traced
  • Z = zombie process
  • Second field = W if the process has no resident pages.
  • Third field = N if the process has a positive nice value
    

Example: ps ax (process status of all processes for all users and system)

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top

This command display a full screen of information of the top processes. It will update automatically until the program is stopped. To stop the display, enter  q

 

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System Info - procinfo

procinfo gathers some system data from the /proc directory and prints it formatted on the screen.

Some of the information displayed is

• Last Boot time
• Load Average
• average number of jobs running
• number of runnable processes
• total number of processes
• PID of the last process run (idem)
• Swap info
• Memory resources
• Number of disks
• IRQ info

• Installed modules (with the -a or -m option)
• File Systems (with the -a or -m option)

  To automatically update the displayed info every 30 seconds

procinfo -fn30
To exit, simply press q