How do I see all running process in Linux?

You need to use the ps command. It provide information about the currently running processes, including their process identification numbers (PIDs). Both Linux and UNIX support ps command to display information about all running process. ps command gives a snapshot of the current processes. If you want a repetitive update of this status, use top command.

  

ps command

Type the following ps command to display all running process:   

# ps aux | less

Where,

• -A: select all processes
• a: select all processes on a terminal, including those of other users
• x: select processes without controlling ttys

See every process on the system

# ps -A
# ps -e

See every process except those running as root

# ps -U root -u root -N

See process run by user vishnu

 # ps -u vishnu

top command

The top program provides a dynamic real-time view of a running system. Type the top at command prompt:

# top

Output:

top command : Displays Linux Tasks

To quit press q, for help press h.

Display a tree of processes

pstree shows running processes as a tree. The tree is rooted at either pid or init if pid is omitted. If a user name is specified, all process trees rooted at processes owned by that user are shown.

$ pstree 

Print a process tree using ps

# ps -ejH
# ps axjf 

Get info about threads

# ps -eLf
# ps axms 

Get security info

# ps -eo euser,ruser,suser,fuser,f,comm,label
# ps axZ
# ps -eM 

Save Process Snapshot to a file

# top -b -n1 > /tmp/process.log

Or you can email result to yourself:

# top -b -n1 | mail -s 'Process snapshot' you@example.com

Lookup process 

Use pgrep command. pgrep looks through the currently running processes and lists the process IDs which matches the selection criteria to screen. For example display firefox process id:

$ pgrep firefox

Following command will list the process called sshd which is owned by root user.

$ pgrep -u root sshd

  

htop and atop

htop is interactive process viewer just like top, but allows to scroll the list vertically and horizontally to see all processes and their full command lines. Tasks related to processes (killing, renicing) can be done without entering their PIDs. To install htop type command:

# apt-get install htop
or
# yum install htop

Now type the htop command at the shell prompt:

# htop

atop program

The program atop is an interactive monitor to view the load on a Linux system. It shows the occupation of the most critical hardware resources (from a performance point of view) on system level, i.e. cpu, memory, disk and network. It also shows which processes are responsible for the indicated load with respect to cpu- and memory load on process level; disk- and network load is only shown per process if a kernel patch has been installed. Type the following command to start atop:

# atop