• Date:

top

• top shows top usage per Process
• Select sort column top -> F or O (select sort field) -> mem

ps

• ps list all process of current user & shell

• ps -U user list all processes of user X

• ps -U user -u all user processes with CPU/MEM

• ps -x show all running processes

• ps -xl show long listing of processes

• ps -xo ppid,user,nice,cputime,args restricting columns to display

• NOTE: ps output can be restricted to some columns only if necessary.

pstree

• pstree shows processes alphabetically in tree format

pgrep

• greps for a process id, takes processname as argument
• pgrep init
• ps -p $(pgrep firefox)
• renice -5 $(pgrep firefox)

iotop

• Shows top io processes

iostat

• Shows io statistics

vmstat

• Show memory statistic of a given time period

    $ vmstat 3  redisplay every 3 seconds
    $ vmstat 3 -o 5 display output five times every 3 seconds

Example output:

    procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
    r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
    2  0      0 180732 182988 1094528    0    0    30    22  321  404 10  3 87  0

• r number of processes waiting for CPU time (CPU might be bottleneck)
• b number of processes waiting for disk time (disk might be bottleneck)
• swpd swapped out processes inadequate memory

free

• free

kill

• Kills a process

    kill 3000   Send SIGTERM to process with PID 3000
    kill -9 12  Send SIGKILL to process with PID 12
    killall -SIGHUP sendmail    have sendmail process reread config file

Signals

• Process signals

 ---------------------------------------------------------------
       Signal     Value     Action   Comment
 ---------------------------------------------------------------
       
       SIGHUP        1       Term    Hangup detected on controlling terminal
                                     or death of controlling process
       SIGINT        2       Term    Interrupt from keyboard
       SIGQUIT       3       Core    Quit from keyboard
       SIGILL        4       Core    Illegal Instruction
       SIGABRT       6       Core    Abort signal from abort(3)
       SIGFPE        8       Core    Floating point exception
       SIGKILL       9       Term    Kill signal
       SIGSEGV      11       Core    Invalid memory reference
       SIGPIPE      13       Term    Broken pipe: write to pipe with no
                                     readers
       SIGALRM      14       Term    Timer signal from alarm(2)
       SIGTERM      15       Term    Termination signal
       SIGUSR1   30,10,16    Term    User-defined signal 1
       SIGUSR2   31,12,17    Term    User-defined signal 2
       SIGCHLD   20,17,18    Ign     Child stopped or terminated
       SIGCONT   19,18,25    Cont    Continue if stopped
       SIGSTOP   17,19,23    Stop    Stop process
       SIGTSTP   18,20,24    Stop    Stop typed at tty
       SIGTTIN   21,21,26    Stop    tty input for background process
       SIGTTOU   22,22,27    Stop    tty output for background process