12 Rsyslog Tips: With Journalctl and Rsyslog Today

Rsyslog is one of the most popular logging solutions for Linux systems. In this article, we’ll cover 12 tips to help you get the most out of rsyslog, including its integration with journalctl.

Tip 1: Basic Configuration

Before diving into advanced topics, it’s essential to understand the basic configuration of rsyslog. The default configuration is usually sufficient for small systems, but as your system grows, so does the complexity of your logging needs.

bash
sudo nano /etc/rsyslog.conf

In this file, you’ll find the default configuration settings. Rsyslog uses a hierarchical configuration approach, where more specific rules override less specific ones.

Tip 2: Prioritize Your Logs

Prioritizing logs is crucial for efficient log management. Use the priority directive to specify the severity level of your logs (e.g., debug, info, warning, etc.).

log
*.debug /var/log/debug.log

This configuration rule sends all debug messages to a separate log file called debug.log.

Tip 3: Use Templates

Templates are an essential feature in rsyslog that allow you to format your logs with placeholders for specific data. This helps you keep track of important information.

rsyslogconf
template(name="MyTemplate" type="string")
/var/log/%$year%_%$month%.log

This configuration rule creates a new log file each day and includes the current year and month in its filename.

Tip 4: Leverage journalctl

journalctl is the system service for querying and displaying logs. It’s the recommended tool for viewing logs, as it can handle high-volume logging scenarios more efficiently than traditional log viewers like tail.

bash
sudo journalctl -f --since=yesterday

This command tail-fs your system logs from yesterday to the present.

Tip 5: Configure rsyslogd with journalctl

To use journalctl with rsyslog, configure rsyslogd to forward its logs to a socket that journalctl can consume.

“`rsyslogconf
module(load=journal)

template(name=”JournalTemplate” type=”string”)
/var/log/journald/%$year%_%$month%.log

input(type=”imjournal”
journald_path=”/run/systemd/journal/dev-log”
journald_rate_limit_interval=5
journald_rate_limit_burst=10
JournalTemplate)

“`

This configuration sets up a journal input that sends logs to /var/log/journald/%$year%_%$month%.log.

Tip 6: Integrate rsyslog with External Logging Systems

Rsyslog provides a flexible framework for integrating your system’s logs with external logging solutions like ELK (Elasticsearch, Logstash, and Kibana) or Splunk.

rsyslogconf
action(type="omfile"
FileCreateMode="0644"
File="/tmp/out.log")

This configuration sends a copy of all log messages to /tmp/out.log.

Tip 7: Use the imudp Module

The imudp module allows rsyslogd to receive logs from other systems over UDP.

rsyslogconf
module(load=imudp)
input(type="imudp" port="514")

This configuration sets up a network input that receives logs on UDP port 514.

Tip 8: Set Up an rsyslog Forwarder

Forwarding logs from one system to another is essential for distributed log management. Use the omfwd module to set up an rsyslog forwarder.

rsyslogconf
module(load=omfwd)
action(type="omfwd"
destination="/tmp/out.log"
protocol="uc"
address="127.0.0.1")

This configuration sets up a forwarder that sends logs to /tmp/out.log on the same machine.

Tip 9: Leverage rsyslog’s High-Performance Features

Rsyslog is designed for high-performance logging scenarios, with features like queueing and buffering that minimize disk I/O.

“`rsyslogconf
module(load=imjournal)
input(type=”imjournal”
journald_path=”/run/systemd/journal/dev-log”
journald_rate_limit_interval=5
journald_rate_limit_burst=10)

“`

This configuration sets up a journal input that takes advantage of rsyslog’s high-performance features.

Tip 10: Automate Log Rotation

Log rotation is an essential aspect of log management. Use the cron job to automate log rotation for your system logs.

bash
0 3 * * * /usr/sbin/logrotate -f /etc/logrotate.conf

This command runs logrotate every morning at 3:00 AM with the configuration defined in /etc/logrotate.conf.

Tip 11: Secure Your Logs

Securing your logs is crucial for maintaining their integrity. Use the rsyslogd configuration to set up secure logging.

“`rsyslogconf
module(load=imuxsock)
input(type=”imuxsock”
/var/log/secure.log
levelinfo)

“`

This configuration sets up a secure input that sends logs to /var/log/secure.log.

Tip 12: Monitor Your Log Files

Monitoring your log files is essential for detecting security threats or performance issues. Use tools like tail or journalctl to monitor your log files.

bash
sudo journalctl -f --since=yesterday

This command tail-fs your system logs from yesterday to the present.

Conclusion

Rsyslog is a powerful logging solution that provides many features and options for efficient log management. With these 12 tips, you can set up secure logging, prioritize your logs, use templates, leverage journalctl, configure rsyslogd with journalctl, integrate with external logging systems, use the imudp module, set up an rsyslog forwarder, take advantage of high-performance features, automate log rotation, secure your logs, and monitor your log files.