5.3: Process Hierarchy
- Page ID
- 77133
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Whilst the operating system can run many processes at the same time, in fact it only ever directly starts one process called the init (short for initial) process. This isn't a particularly special process except that its PID is always 0 and it will always be running.
All other processes can be considered children of this initial process. Processes have a family tree just like any other; each process has a parent and can have many siblings, which are processes created[15] by the same parent.
Certainly children can create more children and so on and so forth.
1 init-+-apmd
|-atd
|-cron
...
5 |-dhclient
|-firefox-bin-+-firefox-bin---2*[firefox-bin]
| |-java_vm---java_vm---13*[java_vm]
| `-swf_play
[15] The term spawn is often used when talking about parent processes creating children; as in "the process spawned a child".