the kernel manage both processes and files

there are many similarities

|           | file           | process          |
|           |                |                  |
| contain   | data           | executable code  |
| in        | disk           | memory           |
| kernel    | create,destroy | create, destroy  |
| show by   | ls [-a,-l...]  | ps [-a, -l...]   |
| have      | attributes     | attributes, too  |
| divided   | into blocks    | into blocks, too |
| structure | tree           | society          |

$ pstree to display a tree of processes

linux convention: add 'd' to a daemon
such as:
systemd to replace init

process files: /proc

man 5 proc to check the process information pseudo-filesystem

procfs - a "pseudo" file system dynamically generated by the kernel to provide information about the status of entries in its process table.

a few commands related to the file /proc

ps, pgrep, pkill, top, pmap, uptime
procps-ng, ng means next generation

procps - the package that has a bunch of small useful utilities that give information about processes using the /proc filesystem. The package includes the programs ps, top, vmstat, w, kill, free, slabtop, and skill.

killall