ps to show an entire tree.

Using ps aux to see active processes is helpful and very common. However, using ps auxf will give an ASCII art representation of the process tree within ps. Here’s an example:

root      3513  0.0  0.0   7196  1068 ?        Ss   Nov30   0:00 /usr/sbin/sshd
root      5201  0.0  0.0  10092  2968 ?        Ss   Nov30   0:00  _ sshd: user [priv]
user      5207  0.0  0.0  11944  3620 ?        S    Nov30   0:11  |   _ sshd: user@pts/1
user      5208  0.0  0.0   5724  2584 pts/1    Ss   Nov30   0:02  |       _ -bash
user     14745  0.0  0.0   5724  1524 pts/1    S    16:42   0:00  |           _ -bash
user     14746  0.0  0.0   3800   500 pts/1    S    16:42   0:00  |           |   _ sleep 100
user     15370  0.0  0.0   5724  1524 pts/1    S    16:52   0:00  |           _ -bash
user     15371  0.0  0.0   3800   472 pts/1    S    16:52   0:00  |           |   _ sleep 100
user     15596  0.0  0.0   4604  1088 pts/1    R+   16:56   0:00  |           _ ps auxf
root      5597  0.0  0.0  10092  2976 ?        Ss   Nov30   0:00  _ sshd: user [priv]
user      5600  0.0  0.0  10244  1844 ?        S    Nov30   0:00  |   _ sshd: user@pts/2
user      5601  0.0  0.0   5720  2536 pts/2    Ss+  Nov30   0:00  |       _ -bash
root      8833  0.0  0.0  10092  2976 ?        Ss   15:17   0:00  _ sshd: user [priv]
user      8835  0.0  0.0  10092  1824 ?        S    15:17   0:00      _ sshd: user@pts/3
root      8836  0.0  0.0   4632  1368 pts/3    Ss+  15:17   0:00          _ /bin/sh

You can see three pseudo terminals created by sshd and a few bash scripts that are running.