Introduction to Processes
Introduction to process
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What is a process?
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.Each running application is called a process.
.Each process are identified by a no. called preocess idification no. (PID)
.PID of ‘init” process is always 1.
init= it is the first process that is started at boot time.,
it is called also grand parent of all the process
* Types of process
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I. foreground process
II. backgroup process
States of process
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Runnable – R
Sleeping – S
Stopped – T
uninterruptiable sleep -D
Zombie (defunct) – Z
Additional states
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Process with high priority – <
,, ,, low ,, – N
,, ,, having pages locked into memory – L
,, ,, np resident pages into memory – W
Note using #pstree (displays process ancestory)
Viewing process states
#ps (displays all the process that are running in the foreground under the control of current terminal
#ps -A (all the terminal
#ps -x (displays all the background prcoess
#ps -l ( ,, long listing of processs)
#ps -u (,, user owner of the process)
#top – (text based process monitoring tool)
PRI= System priority
NI = Nice value (user managed priority)
Altering process scheduling priority
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Max priority (Nice value) –> -20
Min ,, ,, ,, +19
default ,, ,, ,, 0
nice – used to set priority of an application when it is run.
renice – used to after priority of a runing application(process).
#renice -5 -P 1
-5=priority(nice value)
-P=option to specify pid
1=pid of process
Introduction to process (contd…)
Sending signals to process
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kill [signal] [pid]
-15 –> Soft signal (default signal. als o used while processing CTRL+C
[-TERM]
-9
[-kill] –> Strong signal
Killall [signal] [application_name]
-15 to kill the application form all the terminal
-9
Running process into background
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#find / -name httpd.conf >httpdout & (running process in backgroud and print output in httpdout
#find / -name httpd.conf >httpdout 2>httderr &
#jobs – Displays the status of all the background & stopped jobs.
* Stopping a process
#find / -name *.conf
use CTRL+Z to pause the current job (process)
* Resuming stopped process
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#bg %job_id – to resume the stopped process into background
#fg %job_id – to resume the stopped prcoesss into foreground
#kill %job_id – to kill the stopped process