How To Setup SysLog Server on CentOS 7 / RHEL 7

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Today we will be looking into how to set up centralized log management for the Linux server. This will help the Linux admin to have multiple server logs in a single place. The Linux admin not required to login to each server for checking the logs, he can just log in to the centralized server and start to do the monitoring of the log.

Linux labels (auth, cron, FTP, LPR, authpriv, news, mail, syslog, etc,..) the log messages to indicate the type of software that generated the messages with severity (Alert, critical, Warning, Notice, info, etc,..).

You can find more information on Message Labels and Severity Levels

Make sure you have the following to set up a log server.

Two Linux servers ( server and client).

server.itzgeek.local 192.168.0.10

client.itzgeek.local 192.168.0.20

Syslog Server Setup

Install the Rsyslog package, if you do not have it installed.

yum -y install rsyslog

Edit the /etc/rsyslog.conf file.

vi /etc/rsyslog.conf

TCP or UDP

Rsyslog supports both UDP and TCP protocol for receiving logs. TCP protocol provides reliable transmission of logs.

UDP

Uncomment the following to enable the syslog server to listen on the UDP protocol.

FROM:

# Provides UDP syslog reception
#$ModLoad imudp
#$UDPServerRun 514

TO:

# Provides UDP syslog reception
$ModLoad imudp
$UDPServerRun 514

TCP

Uncomment the following to enable the syslog server to listen on the TCP protocol.

FROM:

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# Provides TCP syslog reception
#$ModLoad imtcp
#$InputTCPServerRun 514

TO:

# Provides TCP syslog reception
$ModLoad imtcp
$InputTCPServerRun 514

Restart the syslog service

systemctl restart rsyslog

Verify the syslog server listening on the port 514.

netstat -antup | grep 514

Output:

udp        0      0 0.0.0.0:514             0.0.0.0:*                           1467/rsyslogd       
udp6       0      0 :::514                  :::*                                1467/rsyslogd      

Syslog Client Setup

Install the Rsyslog package, if you do not have it installed.

yum -y install rsyslog

Edit the /etc/rsyslog.conf file.

vi /etc/rsyslog.conf

At the end of the file place the following line to point the client message log to the server.

UDP

*.info;mail.none;authpriv.none;cron.none @192.168.0.10:514

TCP

*.info;mail.none;authpriv.none;cron.none @@192.168.0.10:514

You can use either the hostname or the ip address.

Restart the syslog service

systemctl restart rsyslog

Now all the message logs are sent to the central server and also it keeps the copy locally.

Firewall

Mostly all the production environments are protected by a hardware firewall, ask them to open the TCP & UDP 514.

If you have FirewallD enabled, run the following command on a server in order to accept incoming traffic on UDP / TCP port 514.

TCP

firewall-cmd --permanent --add-port=514/tcp

firewall-cmd --reload

UDP

firewall-cmd --permanent --add-port=514/udp 

firewall-cmd --reload

Validate

Goto the syslog server and view the messages log file.

tail -f /var/log/messages

You should see the client’s logs are being recorded in a syslog server.

Feb  9 04:26:09 client systemd: Stopping System Logging Service...
Feb  9 04:26:09 client rsyslogd: [origin software="rsyslogd" swVersion="8.24.0-41.el7_7.2" x-pid="910" x-info="http://www.rsyslog.com"] exiting on signal 15.
Feb  9 04:26:09 client systemd: Stopped System Logging Service.
Feb  9 04:26:09 client systemd: Starting System Logging Service...
Feb  9 04:26:09 client rsyslogd: [origin software="rsyslogd" swVersion="8.24.0-41.el7_7.2" x-pid="1546" x-info="http://www.rsyslog.com"] start
Feb  9 04:26:09 client systemd: Started System Logging Service.

In this way, you can monitor the other logs such as secure, mail, cron logs, etc.

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Conclusion

That’s All. I hope you successfully set up a centralized syslog server on CentOS 7 / RHEL 7. You can also try open-source log management tools like ELK stack or Graylog for more advanced features such as web interface, correlating log events, etc.

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