Managing processes can be useful for troubleshooting running programs on the operating system.
Commands
ps
ps - display current running processes
3 types of options (UNIX, BSD, GNU) - pick a format and stick with it.
ps
PID TTY TIME CMD
3131 pts/1 00:00:00 bash
3157 pts/1 00:00:00 ps
# Options:
1 UNIX options, which may be grouped and must be preceded by a dash.
2 BSD options, which may be grouped and must not be used with a dash.
3 GNU long options, which are preceded by two dashes.
# Display all the processes for users using BSD syntax
ps ax | less -S
# Display all the processes for users using UNIX syntax
ps -e | less -S
ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.2 0.2 100992 11880 ? Ss 11:03 0:02 /sbin/init splash
root 2 0.0 0.0 0 0 ? S 11:03 0:00 [kthreadd]
root 3 0.0 0.0 0 0 ? I< 11:03 0:00 [rcu_gp]
[...]
ps -ef
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 11:03 ? 00:00:02 /sbin/init splash
root 2 0 0 11:03 ? 00:00:00 [kthreadd]
root 3 2 0 11:03 ? 00:00:00 [rcu_gp]
user 3131 2986 0 11:10 pts/1 00:00:00 bash
root 3238 2 0 11:18 ? 00:00:00 [kworker/1:0-events]
root 3239 2 0 11:19 ? 00:00:00 [kworker/u256:0-events_unbound]
user 3240 3131 0 11:21 pts/1 00:00:00 ps -ef
[...]
# USER = user ID of the process (same premissions as the user)
# PID = process ID (unique for every process)
# PPID = parrent PID - PID of the parrent process that created this process
# C = process utilization percentage
# STIME = start time of the process
# TTY = terminal use of the process (no associated terminal if ?)
# TIME = amount of CPU time used by the process
# CMD = command that started the process
# Display every process running as root
ps -U root -u root u
# Check examples on the manual page
man ps
# Show process hierarchy
ps -eH | less -S
pstree
pstree - display a tree of processes (hierarchy easier to read)
