Processes
The Linux kernel is the core of a Linux installation. The kernel manages memory, provides software with a way to access the hard disk, doles out CPU time, and performs other critical low-level tasks. The kernel is loaded early in the boot process, and it’s the kernel that’s responsible for managing every other piece of software on a running Linux computer.
More about processes
Normally at boot, one process is started /sbin/init. Then everything else is managed by init and are called child processes. (sometimes also referred to as daemons)
Internally, the kernel maintains process information in the process table . Tools such as ps and top (described shortly) enable you to view and manipulate this table.
Process ID numbers
Every process has a PID. Init’s id is normally 1. Each process also has a parent process id(PPID).
ps aux --forestcan help show parent/child relationships
More on Processes
- kill: find the pid and issue the command
- We can also send it a signal like
kill -9 PID - killall: kills by process name instead of pid
- example:
killall -9 testme
Process related commands
- ps , ps aux
- fg
- bg
- control + z
- jobs
- top
- & # to run in background
- sleep
Process states
| code | state |
| D | uninterruptable sleep (I/O is happening) |
| R | running |
| S | interruptable sleep (waiting for event to complete) |
| T | stopped or paused |
| Z | defunct (zombie) |
Process Signals
Messages sent between processes. A numeric value.
Names:
- interrups (Cntrl + c)
- sleep (Cntrl + z)
- kill
- etc..
Process related files
/proc/cpuinfo/proc/meminfo
Last Updated 09/11/2023