Tuesday, March 26, 2013

How to configure syslog server in Linux

Source: http://computernetworkingnotes.com/linux-network-administrations/syslog-server.html

Sample Exam question:- You are a System administrator. Using Log files very easy to monitor the system. Now there are 40 servers running as Mail, Web, Proxy, DNS services etc. Your task is to centralize the logs from all servers into on LOG Server. How will you configure the LOG Server to accept logs from remote host ?

Answer with Explanation

An important part of maintaining a secure system is keeping track of the activities that take place on the system. If you know what usually happens, such as understanding when users log into your system, you can use log files to spot unusual activity. You can configure what syslogd records through the /etc/syslog.conf configuration file.
The syslogd daemon manages all the logs on your system and coordinates with any of the logging operations of other systems on your network. Configuration information for syslogd is held in the /etc/syslog.conf file, which contains the names and locations for your system log files.
By Default system accept the logs only generated from local host. In this example we will configure a log server and will accept logs from client side.
For this example we are using two systems one linux server one linux clients . To complete these per quest of log server Follow this link
Network configuration in Linux
  • A linux server with ip address and hostname Server
  • A linux client with ip address and hostname Client1
  • Updated /etc/hosts file on both linux system
  • Running portmap and xinetd services
  • Firewall should be off on server
We suggest you to review that article before start configuration of log server. Once you have completed the necessary steps follow this guide.
Check syslog, portmap, xinetd service in system service it should be on

 #setup Select  System service from list [*]portmap [*]xinetd [*]syslog 
Now restart xinetd and portmap service
service restart

To keep on these services after reboot on then via chkconfig command

After reboot verify their status. It must be in running condition

service status

Now open the /etc/sysconfig/syslog file
vi syslog

and locate SYSLOGD_OPTIONS tag

add -r option in this tag to accepts logs from clients
syslog editing
-m 0 disables 'MARK' messages.
-r enables logging from remote machines
-x disables DNS lookups on messages recieved with -r

After saving file restart service with service syslog restart command

service syslog restat


On Linux client

ping from log server and open /etc/syslog.conf file

Now go to the end of file and do entry for serve as user.* @ [ server IP] as shown in image
syslog.conf editing

After saving file restart service with service syslog restart command
service syslog restart

Now restart the client so it can send log entry to server. ( Note that these logs will generate when client boot, so do it restart not shutdown)


Check clients log on Log server

To check the message of client on server open
less messages

In the end of this file you can check the log from clients
messages file

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