Mastering killall: 8 Practical Ways to Terminate Linux Processes

1. Basic usage

If three processes named hello1, hello2 and hello3 are running, you can terminate hello1 with a simple command: killall hello1 The process disappears from the process list, confirming the termination.

2. Killing all processes of a specific user

To stop every process started by user harry, use the -u option. This sends the default SIGTERM signal to each of the user’s processes. killall -u harry Be cautious: this also terminates the user’s login shells, which may log the user out.

3. Terminating processes based on runtime

Use -o (older) to kill processes that have been running longer than a specified period, e.g., five hours: killall -o 5h Conversely, -y (younger) kills processes that have run for less than the given time, such as four hours: killall -y 4h Both options are aggressive and may also close the terminal.

4. Ignoring case

By default, killall matches case‑sensitively. Adding -I makes the match case‑insensitive:

killall -I HELLO1

5. Suppressing output

To run the command silently, add the -q (quiet) flag:

killall -q HELLO2

6. Listing and sending specific signals

Use -l to list all signals supported by killall: killall -l To send a particular signal, use -s followed by the signal name, e.g., killall -s KILL processname.

7. Interactive mode

If you want to confirm each termination, add -i. The command will prompt you for each matching process:

killall -i hello*

8. Waiting for termination

The -w (wait) option makes killall pause until the targeted process has fully exited before returning control: killall -w hello1 This can be useful in scripts where subsequent actions depend on the process being completely stopped.