Program ?
- process if different from a program.
- Program under execution is a process.
- Program is set of instructions.
INIT: Mother of all the processes.
- Fork: if there is process P1 can fork out into multiple processes which are identical,Independent P1 and P2 with different PID’s.
- Exec:
- Wait:
Rights of Process
- Who am i ? what is its pid
- who is my parent ? what is my parent process id
- what happened to my child ?
Orphan Process :
the process whose parent died,when a parent process is killed the INIT process takes the responsibility that's the reason its called mother of all the processes.
Zombie Process :
A process
PS
processes running on your terminal
[trainee@localhost purna]$ ps
PID TTY TIME CMD
6188 pts/14 00:00:00 bash
6507 pts/14 00:00:00 ps
number of processes running
[trainee@localhost purna]$ ps -e|wc -l
164
processes running on a terminal pts/3
[trainee@localhost purna]$ ps -tpts/3
PID TTY TIME CMD
4300 pts/3 00:00:00 bash
6612 pts/3 00:00:00 cat
DAEMON
Disk And Execution Monitor
JOBS
will print all the jobs which are stopped or paused .
to resume these jobs one can use fg or bg (foreground or background) %JOB_NUMBER
KILL
list all signals
[trainee@localhost purna]$ kill -l
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL
5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE
9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2
13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT
17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU
25) SIGXFSZ 26) SIGVTALRM 27) SIGPROF 28) SIGWINCH
29) SIGIO 30) SIGPWR 31) SIGSYS 34) SIGRTMIN
35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+338)SIGRTMIN+4}Dummy signals
39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8
43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12
47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14
51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10
55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7 58) SIGRTMAX-6
59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2
63) SIGRTMAX-1 64) SIGRTMAX
Kill A Process
[trainee@localhost purna]$ kill -s SIGKILL 4524
where 4524 is the process id
Nice
the lesser the Nice value the higher the priority
only the root can make the priority higher or nice value to low.
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