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Hi,
I will explain how to Manage and Monitor Process Commands in this tutorial series.
Read previous article before this.
https://ittutorial.org/linux-commands-tutorial-for-beginners-3-system-statistic-commands/
Manage and Monitor Process Commands
Before explaining Linux Process management and monitor commands, let’s look what is the Process concept.
Process: The name given to each part of the programs running on the operating systems. Processes hold code of the program that is currently running and the functions it performs.
In general, Processes contain the following structures.
- Running Program
- Asynchronous function related with Program
- A task specified by the processor
The commands in Linux that are related to the Processes or that monitor and management of the Processes are as follows.
- ps
- kill
- killall
- bg
- fg
- pidof
- pgrep
- pstree
- fork
- getpid
- getppid
- exec
- pipe
Before explain the process management commands, I want to remind you again and again an important command. This is the “man” command. With this command, you can learn the commands that you hear but want to learn in detail.
It provides the user with detailed information about the functions of the command and the parameters it receives when used with these parameters.
Now, as an example, we refer to our man command to learn “lastcomm”. Its usage and output are as follows.
ps command
With this command, all processes running on the Operating system and process ids of these processes are displayed to the user.
Use and output of the command are as follows.
You can use ” -ef ” option with this command to see details of processes.
[root@MehmetSalih ~]# [root@MehmetSalih ~]# ps PID TTY TIME CMD 27473 pts/3 00:00:00 bash 27711 pts/3 00:00:00 ps [root@MehmetSalih ~]# [root@MehmetSalih ~]# ps -ef UID PID PPID C STIME TTY TIME CMD root 1 0 0 Sep24 ? 00:00:01 /sbin/init root 2 0 0 Sep24 ? 00:00:01 [kthreadd] root 3 2 0 Sep24 ? 00:00:00 [ksoftirqd/0] root 5 2 0 Sep24 ? 00:00:00 [kworker/0:0H] root 6 2 0 Sep24 ? 00:00:00 [kworker/u:0] root 7 2 0 Sep24 ? 00:00:00 [kworker/u:0H] root 8 2 0 Sep24 ? 00:00:00 [migration/0] root 9 2 0 Sep24 ? 00:00:00 [rcu_bh] root 10 2 0 Sep24 ? 00:00:34 [rcu_sched] root 11 2 0 Sep24 ? 00:00:00 [watchdog/0] .............. .............. [root@MehmetSalih ~]#
kill command
With this command, a process can be terminated by typing the ids of the existing processes in the operating system. In Linux systems, only the priviliged user like Root who has the privilige on that process can kill it.
root 16200 2 0 Sep24 ? 00:00:02 [kworker/5:2] oracle 16569 11394 0 Sep24 pts/1 00:00:00 sqlplus as sysdba oracle 16572 16569 0 Sep24 ? 00:00:00 oracleDeveci (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq))) root 16961 2 0 Sep24 ? 00:00:00 [kworker/11:1] root 18422 2 0 Sep24 ? 00:00:00 [kworker/3:2] root 18973 2 0 09:45 ? 00:00:00 [kworker/7:2] root 20963 2 0 10:00 ? 00:00:00 [kworker/2:2] root 21978 2 0 10:04 ? 00:00:00 [kworker/14:2] root 22687 2 0 10:10 ? 00:00:00 [kworker/15:2] postfix 25510 8689 0 10:28 ? 00:00:00 pickup -l -t fifo -u root 26222 2 0 00:40 ? 00:00:00 [kworker/1:0] root 26485 2 0 10:32 ? 00:00:00 [kworker/13:1] root 26585 2 0 10:33 ? 00:00:00 [kworker/12:0] root 27230 2 0 10:38 ? 00:00:00 [kworker/12:2] root 27308 2 0 10:39 ? 00:00:00 [kworker/13:0] root 27468 8598 0 10:40 ? 00:00:00 sshd: root@pts/3 root 27473 27468 0 10:40 pts/3 00:00:00 -bash root 27545 2 0 10:40 ? 00:00:00 [kworker/14:0] oracle 27692 1 0 10:42 ? 00:00:00 oracle+ASM_pr00_Deveci (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq))) root 27716 27473 0 10:42 pts/3 00:00:00 ps -ef [root@MehmetSalih ~]# [root@MehmetSalih ~]# [root@MehmetSalih ~]# kill -9 16569 [root@MehmetSalih ~]#
killall command
This command terminates all processes of any programs whose names are provided to it as arguments (i.e., inputs).
killall [options] program_name(s)
For example: You want to kill all processes of java,apache or Oracle user, you can use following command.
[root@MehmetSalih ~]# killall -9 java [root@MehmetSalih ~]# killall -9 apache [root@MehmetSalih ~]# killall -9 oracle
bg ( back ground ) command
This command may not be available on all Linux distributions. This command resumes any stopped process in the background
It also lists the tasks currently running on the system.
For example, I will trigger and run any process, then i will stop it manually and will run bg command to resume this process in the background.
[oracle@MehmetSalih ~]$ bg -bash: bg: current: no such job [oracle@MehmetSalih ~]$ [oracle@MehmetSalih ~]$ crontab -l 00 02 * * * sh /home/oracle/scripts/full_backup.sh [oracle@MehmetSalih ~]$ [oracle@MehmetSalih ~]$ [oracle@MehmetSalih ~]$ sh /home/oracle/scripts/full_backup.sh Recovery Manager: Release 12.1.0.2.0 - Production on Wed Sep 25 11:18:58 2019 Copyright (c) 1982, 2014, Oracle and/or its affiliates. All rights reserved. connected to target database: Deveci (DBID=152543005, not open) RMAN> run{ 2> ALLOCATE CHANNEL CH1 DEVICE TYPE DISK; 3> delete noprompt archivelog all completed before 'sysdate-4'; 4> crosscheck backup; 5> delete expired backup; 6> RELEASE CHANNEL CH1; 7> } 8> using target database control file instead of recovery catalog ^Z [1]+ Stopped sh /home/oracle/scripts/full_backup.sh [oracle@MehmetSalih ~]$ allocated channel: CH1 channel CH1: SID=290 device type=DISK [oracle@MehmetSalih ~]$ bg [1]+ sh /home/oracle/scripts/full_backup.sh & [oracle@MehmetSalih ~]$ [oracle@MehmetSalih ~]$
fg command
This command allows a background process to run in the foreground.
Now I will use fg command for above example like following.
[oracle@MehmetSalih ~]$ bg [1]+ sh /home/oracle/scripts/full_backup.sh & [oracle@MehmetSalih ~]$ [oracle@MehmetSalih ~]$ [oracle@MehmetSalih ~]$ fg sh /home/oracle/scripts/full_backup.sh specification does not match any backup in the repository specification does not match any backup in the repository released channel: CH1 Recovery Manager complete. [oracle@MehmetSalih ~]$ [oracle@MehmetSalih ~]$
pidof command
This command displays the process id of a program on the operating system.
[root@MehmetSalih ~]# pidof init 1 [root@MehmetSalih ~]# [root@MehmetSalih ~]# [root@MehmetSalih ~]# pidof firefox 63 [root@MehmetSalih ~]#
pgrep command
With this command, the id of a currently running process is displayed to the user.
The usage of the command is as follows.
pstree command
This command displays the processes running on the system to the user as a tree.
Use of the command is as follows.
fork command
This is the command that creates a child process running on linux and unix systems. After the process is copied, there are two processes, parent-child in the operating system. This command is usually used to perform a different function on the operating system. Thus, the child process created with this command can see different functions on the operating system.
getpid command
This command displays the user id of the current running process.
getppid command
This command gives the user parent id of the current running process.
exec command
This command allows a process to continue as a different program on linux systems. After this process, the process id and control block do not change. The Exec command works in 6 different ways depending on the parameters it receives and the functions it sees. These and the parameters they get are as follows.
int execl(const char *path, const char *arg0, ... /*,(char *) 0 */); int execv(const char *path, char *const argv[]); int execle(const char *path, const char *arg0, ... /*, (char *) 0, char *const envp[] */); int execve(const char *path, char *const argv[], char *const envp[]); int execlp(const char * file, const char *arg0, ... /*, (char *) 0 */); int execvp(const char *file, char *const argv[]);
pipe | command
With this command, you can use any command’s output as input to another command. The “|” sign is used for this.
Use and output of the command are as follows.
Now output of ps -ef command will be used by grep command. After that output of grep command will be used by wc command.
[root@MehmetSalih ~]# [root@MehmetSalih ~]# ps -ef | grep smon root 5804 27473 0 11:45 pts/3 00:00:00 grep smon oracle 11132 1 0 Sep24 ? 00:00:01 asm_smon_+ASM oracle 11317 1 0 Sep24 ? 00:00:00 ora_smon_DEVECI [root@MehmetSalih ~]# [root@MehmetSalih ~]# [root@MehmetSalih ~]# ps -ef | grep smon | wc 3 25 182 [root@MehmetSalih ~]#
I will continue to explain Linux command tutorials in the next article.
