Discover an effective way to set PostgreSQL schemas using PHP PDO when the SET search_path approach fails. Learn best practices for schema-based architecture.
Some of the important server related problems will be solved only using shell access to the server. To access the cPanel server shell using SSH, there must be an SSH client installed on PC. Most of the Linux distros include SSH client software by default. If it is not installed, then it can be easily installed with following commands,
For Ubuntu:apt-get install openssh-client For CentOS:yum install openssh-clients
After installation, follow these steps to access the cPanel shell with SSH from Linux:
Login to cPanel and go to Security > SSH/Shell Access to generate SSH key pair.
Click Manage SSH Keys > Generate a New Key. You should use a password to protect the key. You will be asked the password each time you use the key.
In Public Keys section click ‘Manage Authorization’ and ‘Authorize’
In Private Keys section click, Vew/Download then download the key (id_dsa or id_rsa) to your PC.
Save it to ~/.ssh directory on your Linux machine under a meaningful name to not overwrite your existing keys for example id_dsa.myjavahost
Now make sure permissions are correct on the key (one-time task) and connect: mypc:~$ chmod 600 .ssh/id_dsa mypc:~$ ssh -p1033 -i .ssh/id_dsa yourusername@yourservername Enter passphrase for key '.ssh/id_dsa':
Provide the password for the key, set up in step #2
Learn to schedule tasks using cronjob in Unix. This guide explains how to manage cronjob tasks in unix with practical examples.
Cron jobs are essential tools in Unix/Linux systems for automating repetitive tasks. Whether you’re backing up files, syncing data, or running maintenance scripts, cron jobs make sure your tasks run consistently and on time without manual intervention.
In this article, we’ll walk through how to add jobs to the cron scheduler (crontab) and understand its syntax so you can schedule tasks efficiently.
What is a Cron Job in Unix?
A cron job is a scheduled command or script that runs automatically at specified intervals. The cron daemon (crond) handles these jobs in the background on Unix-like operating systems.
Viewing and Editing Crontabation files
Each user has their own crontab file. To view or edit your crontab:
crontab -e
This command opens your crontab in the default system editor (like vi or nano), allowing you to add or modify jobs.
To view your current scheduled jobs:
crontab -l
To remove all scheduled cron jobs:
crontab -r
Unix Cron jobs Syntax Breakdown
A typical cron job line looks like this:
* * * * * command to be executed - - - - - | | | | | | | | | ----- Day of week (0 - 7) (Sunday=0 or 7) | | | ------- Month (1 - 12) | | --------- Day of month (1 - 31) | ----------- Hour (0 - 23) ------------- Minute (0 - 59)
Each * represents a time or date field. And each field can be configured based on the following table.
Field
Value Range
Description
Minute
0–59
Minute of the hour
Hour
0–23
Hour of the day
Day
1–31
Day of the month
Month
1–12
Month of the year
Weekday
0–7 (0 or 7 = Sunday)
Day of the week
Example: Run backup cron job script
If you wished to have a script named /root/backup.sh run every day at 3 am, your crontab entry would look like as follows. First, install your cronjob by running the following command:
# crontab -e
Append the following entry:
0 3 * * * /root/backup.sh
Save and close the file.
More examples
To run /path/to/command five minutes after midnight, every day, enter:
5 0 * * * /path/to/command
Run /path/to/script.sh at 2:15 pm on the first of every month, enter:
15 14 1 * * /path/to/script.sh
To run any PHP script /scripts/phpscript.php at 10 pm on weekdays, enter:
0 22 * * 1-5 /scripts/phpscript.php
Run /root/scripts/perl/perlscript.pl at 23 minutes after midnight, 2am, 4am …, everyday, enter:
23 0-23/2 * * * /root/scripts/perl/perlscript.pl
Run /path/to/unixcommand at 5 after 4 every Sunday, enter:
5 4 * * sun /path/to/unixcommand
You can schedule any command using the cron jobs. For running any script using cron job, make sure your script has executable permissions.
If your script uses environment variables or specific paths, be sure to define them inside the script or call the appropriate environment setup.
Redirecting Output
To log output or errors, you can use the following command and save the logs in file:
2>&1 redirects errors (stderr) to the same log file without displaying it to the console.
System-Wide Cron Jobs
System-wide cron files can be added to:
Hourly, daily, weekly, monthly: /etc/cron.hourly/, /etc/cron.daily/, etc.
/etc/crontab
/etc/cron.d/
Conclusion
Cron jobs are powerful for scheduling recurring tasks in Unix/Linux environments. By mastering crontab syntax and scheduling structure, you can automate system maintenance, backups, and custom scripts with ease.
Make sure to test your scripts before scheduling them and check logs regularly to confirm successful execution.
