Unix for Advanced Users - The Unix Boot Sequence

9. The Unix Boot Sequence

9.4. Dummy Process Creation

Depending on the Unix flavor, the kernel now creates the first Unix processes. A number of dummy processes (processes which cannot be killed) are created first to handle crucial system functions. A ps -ef listing on each OS shows what these processes are:

HP-UX 10.20:

   UID     PID  PPID C  STIME   TTY       TIME COMMAND
   root     0     0  0  Apr 20  ?         0:17 swapper
   root     1     0  0  Apr 20  ?         0:00 init
   root     2     0  0  Apr 20  ?         1:02 vhand

* swapper - dummy process which provides swapping services
* vhand - dummy process providing virtual memory (paging) service

Linux RedHat 6.0:

   UID        PID  PPID  C STIME TTY      TIME CMD
   root         1     0  0 09:59 ?        00:00:07 init
   root         2     1  0 09:59 ?        00:00:00 [kflushd]
   root         3     1  0 09:59 ?        00:00:00 [kpiod]
   root         4     1  0 09:59 ?        00:00:00 [kswapd]
   root         5     1  0 10:00 ?        00:00:00 [mdrecoveryd]

* kflushd - dummy process to handle the swapping activity
* kpiod - dummy process to handle I/O activity
* kswapd - dummy process to handle the swapping activity
* mdrecoveryd - dummy process to handle the recovery of threads

Solaris:

   UID   PID  PPID  C    STIME TTY      TIME CMD
   root     0     0  0   Apr 19 ?       0:00 sched
   root     1     0  0   Apr 19 ?       0:22 /etc/init -
   root     2     0  0   Apr 19 ?       0:00 pageout

* sched - dummy process which provides swapping services
* pageout - dummy process which provides virtual memory (paging) services

Other dummy processes you might see under other Unixes are bdflush or update (both are used to handle file system I/O).

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