How to Setup Central Log Server using Rsyslog on CentOS 6.2/CentOS 6.3

In this post i will share on how to setup Central log server using Rsyslog on linux CentOS 6.2 and it’s also working on CentOS6.3. This rsyslog central server will archive all logging messages(/var/log/messages) from it’s client. This logging messages might be helpful as these logs are very critical for system administrator for troubleshooting purpose.

/var/log/messages – Contains global system messages, including the messages that are logged during system startup. There are several things that are logged in /var/log/messages including mail, cron, daemon, kern, auth, etc.

Assumed that the central log server and client ip address are as below :

Central rsyslog Server : 192.168.1.55(syslogserver)
Rsyslog client : 192.168.1.54(rsyslogclient)

Configure Central Rsyslog Server :

1. Login to Central Rsyslog Server. First we need to backup default rsyslog.conf configuration :

[root@rsyslogserver ~]# cp /etc/rsyslog.conf /etc/rsyslog.conf.bak

2. Modify rsyslog configuration files :

[root@rsyslogserver ~]# vi /etc/rsyslog.conf

3. Loads the modules we need :

#### MODULES ####

$ModLoad imuxsock.so    # provides support for local system logging (e.g. via logger command)
$ModLoad imklog.so      # provides kernel logging support (previously done by rklogd)
$ModLoad immark.so      # provides --MARK-- message capability

4. Listen on tcp and udp 514 :

# Provides UDP syslog reception
$ModLoad imudp.so
$UDPServerAddress 0.0.0.0
$UDPServerRun 514

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

5. Sets the default templates :

# Use default timestamp format
$ActionFileDefaultTemplate RSYSLOG_TraditionalFileFormat

6. Implement logging rules :

#### RULES ####

# Log all kernel messages to the console.
# Logging much else clutters up the screen.
#kern.*                                                 /dev/console

# Log anything (except mail) of level info or higher.
# Don't log private authentication messages!
*.info;mail.none;authpriv.none;cron.none                /var/log/messages

# The authpriv file has restricted access.
authpriv.*                                              /var/log/secure

# Log all the mail messages in one place.
mail.*                                                  -/var/log/maillog


# Log cron stuff
cron.*                                                  /var/log/cron

# Everybody gets emergency messages
*.emerg                                                 *

# Save news errors of level crit and higher in a special file.
uucp,news.crit                                          /var/log/spooler

# Save boot messages also to boot.log
local7.*                                                /var/log/boot.log

7. Add the followings line in the forwarding rule :

# ### begin forwarding rule ###
..
..
#
# This one is the template to generate the log filename dynamically, depending on the client's IP address.
$template FILENAME,"/var/log/rsyslog/%fromhost-ip%/messages-%$YEAR%-%$MONTH%-%$DAY%.log"
#
# Log all messages to the dynamically formed file. Now each clients log (192.168.1.2, 192.168.1.3,etc...), will be under a separate directory which is formed by the template FILENAME.
*.* ?FILENAME
..
..
# ### end of the forwarding rule ###

8. Create rsyslog folder under /var/log :

[root@rsyslogserver ~]# mkdir /var/log/rsyslog

9. After adding the above lines to the rsyslog.conf, you need to restart the rsyslog process and it’s will ready to accept messages from configured client :

[root@rsyslogserver ~]# service rsyslog restart
Shutting down system logger:                               [  OK  ]
Starting system logger:                                    [  OK  ]

Configure Rsyslog Remote Client :

1. Login to individual client machines and set the following :

[root@rsyslogclient ~]# vim /etc/rsyslog.conf

2. Loads the modules we need :

#### MODULES ####

$ModLoad imuxsock.so    # provides support for local system logging (e.g. via logger command)
$ModLoad imklog.so      # provides kernel logging support (previously done by rklogd)
$ModLoad immark.so      # provides --MARK-- message capability

3. Enable “*.* @192.168.1.55:514” at the forwarding rule :

# ### begin forwarding rule ###
# The statement between the begin ... end define a SINGLE forwarding
# rule. They belong together, do NOT split them. If you create multiple
# forwarding rules, duplicate the whole block!
# Remote Logging (we use TCP for reliable delivery)
#
# An on-disk queue is created for this action. If the remote host is
# down, messages are spooled to disk and sent when it is up again.
#$WorkDirectory /var/lib/rsyslog # where to place spool files
#$ActionQueueFileName fwdRule1 # unique name prefix for spool files
#$ActionQueueMaxDiskSpace 1g   # 1gb space limit (use as much as possible)
#$ActionQueueSaveOnShutdown on # save messages to disk on shutdown
#$ActionQueueType LinkedList   # run asynchronously
#$ActionResumeRetryCount -1    # infinite retries if host is down
# remote host is: name/ip:port, e.g. 192.168.0.1:514, port optional
*.*  @192.168.1.55:514
# ### end of the forwarding rule ###
#

4. Restart the rsyslog service on the client :

[root@rsyslogclient ~]# service rsyslog restart
Shutting down system logger:                               [  OK  ]
Starting system logger:                                    [  OK  ]

Verification :

Login and verify the log files from central rsyslog server, rsyslogserver :

[root@rsyslogserver ~]# ls /var/log/rsyslog/192.168.1.54/
messages-2012-09-16.log

Check the log :

[root@rsyslogserver ~]# tail -f /var/log/rsyslog/192.168.1.54/messages-2012-09-16.log
Sep 16 11:45:48 rsyslogclient ntpd[1359]: synchronized to 212.26.18.43, stratum 1
Sep 16 11:46:34 rsyslogclient clamd[1367]: SelfCheck: Database status OK.
Sep 16 11:53:47 rsyslogclient ntpd[1359]: time reset +2.330541 s
Sep 16 11:56:36 rsyslogclient clamd[1367]: SelfCheck: Database status OK.
Sep 16 11:58:32 rsyslogclient ntpd[1359]: synchronized to 212.26.18.43, stratum 1
Sep 16 12:01:01 rsyslogclient CROND[11208]: (root) CMD (run-parts /etc/cron.hourly)
Sep 16 12:01:01 rsyslogclient run-parts(/etc/cron.hourly)[1120 starting 00awstats
Sep 16 12:01:01 rsyslogclient run-parts(/etc/cron.hourly)[1121 finished 00awstats
Sep 16 12:01:01 rsyslogclient run-parts(/etc/cron.hourly)[1120 starting 0anacron
Sep 16 12:01:01 rsyslogclient run-parts(/etc/cron.hourly)[1122 finished 0anacron
Sep 16 12:06:36 rsyslogclient clamd[1367]: SelfCheck: Database status OK.

4 Replies to “How to Setup Central Log Server using Rsyslog on CentOS 6.2/CentOS 6.3”

    1. Thanks for mentioning this. I’ve been running in loops for a while now. Everything seems configured properly, but client won’t even attempt to send anything to a server (judging by tcpdump’s output).

  1. Nice, entries go into message log, but also pop up on console and any open terminal screen as well.  Need something to suppress this.

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