Tutorial 35-39

Q1 Custom systemd Service and Timer Creation

Configure a custom systemd service and associated timer to perform automated metric logging on a recurring schedule.

Requirements

Create a service unit file named /etc/systemd/system/syslog-check.service.
- The service must be of type oneshot.
- It must execute the command /usr/bin/logger "RHCSA Performance Check Active" upon activation.
Create a timer unit file named /etc/systemd/system/syslog-check.timer.
- The timer must trigger syslog-check.service.
- The timer must execute every Monday through Friday at 08:30:00 and 16:30:00.
Ensure the timer starts automatically upon system boot and is activated (not start) immediately without restarting the system.

Solution

Create .service unit file
- sudo touch /etc/systemd/system/syslog-check.service
Open .service unit file by vim
- sudo vim /etc/systemd/system/syslog-check.service
Write content of .service unit file
- Press I to enter insert mode

[Unit]

Description=automated metric logging

[Service]

Type=oneshot

ExecStart=/usr/bin/logger "RHCSA Performance Check Active"

Save and exit
- Esc --> :wq
Verify .service file content
- cat /etc/systemd/system/syslog-check.service
Create .timer unit file
- sudo touch /etc/systemd/system/syslog-check.timer
Open .timer unit file by vim
- sudo vim /etc/systemd/system/syslog-check.timer
Write content of .timer unit file
- Press I to enter insert mode

[Unit]

Description=automated metric logging timer

[Timer]

OnCalendar=Mon..Fri *-*-* 08,16:30:00

[Install]

WantedBy=timers.target

Save and exit
- Esc --> :wq
Verify .timer file content

- cat /etc/systemd/system/syslog-check.timer

Verify calendar expression
- systemd-analyze calendar "Mon..Fri *-*-* 08,16:30:00"
Reload the systemd
- systemctl daemon-reload
Enable the timer

systemctl enable --now syslog-check.timer

Verify timer
- systemctl status syslog-check.service
- systemctl status syslog-check.timer
- systemctl list-timers syslog-check.timer
Cleanup
- systemctl stop syslog-check.timer
- sudo systemctl disable --now syslog-check.timer
- sudo systemctl stop syslog-check.service
- rm -f /etc/systemd/system/syslog-check.service
- rm -f /etc/systemd/system/syslog-check.timer
- sudo systemctl daemon-reload

Q2 Service Performance Monitoring and Automated Execution

Install system performance metrics tooling and configure automated system performance collection.

Requirements

Install the sysstat package on the system.
Enable and start the default systemd timer provided by sysstat to gather performance metrics automatically.
Trigger an immediate metric capture manually via systemd without modifying or waiting for the schedule.
Verify that performance collection logs are populated using the sar utility.

Solution

Install sysstat
- dnf install -y sysstat
Enable timer
- sudo systemctl enable --now sysstat-collect.timer
Start timer
- sudo systemctl start sysstat-collect.service
Verify timer status
- systemctl status sysstat-collect.timer
Verify performance collection logs
- sar -A

Q3 User Crontab Scheduling

Configure scheduled background execution for a specific system user using crontab.

Requirements

Configure a cron task for user student (or your non-root user).
The task must execute every 15 minutes between 09:00 and 17:00, only on Saturdays.
The command to execute is: /usr/bin/echo "Maintenance Window Active" >> /tmp/maintenance.log 2>&1
Do not edit system-wide cron files (/etc/crontab or /etc/cron.d/); configure this within the designated user's cron spool.

Solution

Open crontab
- crontab -e -u student
Edit command in crontab
- Press Esc --> I
- Example: */15 9-17 * * SAT /usr/bin/echo "Maintenance Window Active" >> /tmp/maintenance.log 2>&1
Press Esc --> :wq --> Enter to save.
Verify command
- crontab -l -u student
Remove the crontab job
- crontab -r -u student
Verify
- crontab -l -u student
Remove the output log file
- sudo rm -f /tmp/maintenance.log

Q4 One-Time Execution via at

Schedule a single, non-recurring delayed job using atd.

Requirements

Ensure the atd service is active and set to start automatically on system boot.
Schedule a one-time execution job to run 20 minutes from the current system time.
The job must create a file at /tmp/at_execution_flag.txt containing the system hostname (hostname > /tmp/at_execution_flag.txt).

Solution

Enable and start the atd service
- systemctl enable --now atd
- systemctl start atd
- systemctl status atd
Run at command at specific time
- at now + 20 minutes
Add command to create file when time reach
- hostname > /tmp/at_execution_flag.txt
Press Enter --> Ctrl+D to stop edit command
List all active jobs of at command
- atq
Wait till time passed
- date
List all file under the directory and find the file
- ls /tmp
Verify content
- cat /tmp/at_execution_flag.txt
Cleanup
- rm -rf /tmp/at_execution_flag.txt

Q5 Temporary Directory and File Lifecycle Management

Configure systemd-tmpfiles to manage temporary directory persistence and automatic file cleanup rules.

Requirements

Create a custom configuration file named /etc/tmpfiles.d/custom-cleanup.conf.
Define a rule that automatically manages a directory at /var/tmp/app_cache:
- Type: Directory creation (d)
- Ownership: User root, Group root
- Permissions: 0775
- Age limit: Clean up any files/directories older than 5 days (5d)
Define a second rule within the same file for /tmp/volatile_data:
- Type: Directory creation (d)
- Ownership: User root, Group root
- Permissions: 0700
- Age limit: Clean up any files older than 12 hours (12h)
Enforce the creation of these paths immediately using systemd-tmpfiles without rebooting the system.

Solution

Create configuration file
- sudo vim /etc/tmpfiles.d/custom-cleanup.conf
Press Esc --> I to add command
- d /var/tmp/app_cache 0775 root root 5d
- d /tmp/volatile_data 0700 root root 12h
Press Esc --> :wq to save and quit.
Run create command
- systemd-tmpfiles --create /etc/tmpfiles.d/custom-cleanup.conf;
Confirm permissions is
- drwxrwxr-x (0775), owned by root user and root group.
- ls -ld /var/tmp/app_cache
- drwx------ (0700), owned by root user and root group.
- ls -ld /tmp/volatile_data
Cleanup
- systemd-tmpfiles --remove /etc/tmpfiles.d/custom-cleanup.conf;
- rm /etc/tmpfiles.d/custom-cleanup.conf
- sudo rmdir /var/tmp/app_cache
- sudo rmdir /tmp/volatile_data
- ls -ld /var/tmp/app_cache /tmp/volatile_data /etc/tmpfiles.d/custom-cleanup.conf

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