Introduction
Managing jobs in Ubuntu is a foundational skill for system administrators, developers, and power users. This tutorial will guide you through various commands and utilities you can use to effectively manage application processes on your system.
Understanding Jobs and Processes
Before diving into managing jobs, it’s important to differentiate between processes and jobs. A process is an instance of a program running, whereas a job is a process that a shell is aware of and managing. Jobs can be suspended, resumed, and terminated from the shell.
Managing Jobs with Basic Commands
List Active Jobs
jobs
This will list all current jobs with their statuses: running, stopped, or terminated.
`Output:
[1]+ Running gedit &
[2]+ Stopped firefoxSuspending and Resuming Jobs
To suspend a running job, you can use the Ctrl+Z keystroke:
ping google.com
Ctrl+Z
You’ll see:
[1]+ Stopped ping google.com
Resume a job in the foreground with:
fg %1
Or resume a job in the background with:
bg %1
Killing a Job
To terminate a job, use the kill command with the job identifier:
kill %1
The job will terminate, and you’ll receive a confirmation:
[1]+ Terminated ping google.com
Advanced Job Management with at and cron
The at Command
The at command schedules a job for a one-time execution at a specified time. For example:
echo "uptime" | at now + 5 minutes
The system will execute “uptime” after 5 minutes. The at daemon (atd) must be running for this to work.
The cron Command
The cron daemon is used for scheduling recurring jobs. Modify the crontab file to create a new scheduled job:
crontab -e
You can add this line to create a job that runs every hour:
0 * * * * /path/to/script.sh
Using systemd for Job Scheduling
In Ubuntu, systemd is the init system that manages system processes after booting. It incorporates job scheduling with services and timers.
Creating a Custom Service and Timer
Create a service unit file at /etc/systemd/system/myjob.service:
[Unit]
Description=My custom job
[Service]
Type=oneshot
ExecStart=/path/to/myjob.sh
Create a corresponding timer unit file at /etc/systemd/system/myjob.timer:
[Unit]
Description=Run myjob.service every hour
[Timer]
OnCalendar=*-*-* *:00:00
[Install]
WantedBy=timers.target
Enable and start the timer with:
systemctl enable myjob.timer
systemctl start myjob.timer
Conclusion
This tutorial covered the essentials of job management in Ubuntu, from controlling jobs in the shell to utilizing at, cron, and systemd for scheduling. With practice, these skills will enhance your ability to manage Linux processes efficiently.
