How to MRTG on Linux
Step # 1 : Make sure snmp server installed
Please note that snmpd configuration does not require using mrtg with remote network devices such as Routers and switches. If you just want mrtg graphs for router or switch then please refer to step # 4 (as all these devices comes preconfigured with snmpd software).
Run rpm commands query option to find out snmp server installed or not:
# rpm -qa | grep snmp If snmp installed then please refer step # 2; otherwise snmp server and utils were not present and your need to install them using following steps (login as a root user):
(a) Visit rpmfind.net to get snmp server and utilities rpms. If you are fedora user then use yum command as follows to install it:
# yum install net-snmp-utils net-snmp (b) If you are RHEL subscriber then use up2date command as follows to install:
#up2date -v -i net-snmp-utils net-snmp Step # 2 : Determine if snmp server is running or not
Run 'ps' command to see if snmp server is running or not:
# ps -aux | grep snmp Output:
root 5512 0.0 2.3 5872 3012 pts/0 S 22:04 0:00 /usr/sbin/snmpd
Alternatively, you can try any of the following two commands as well:
# lsof -i :199 Output:
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
snmpd 5512 root 4u IPv4 34432 TCP *:smux (LISTEN)
OR try out netstat command:
# netstat -natv | grep ':199' Output:
tcp 0 0 0.0.0.0:199 0.0.0.0:* LISTEN
If you found service is running or listing on port 199 then please see step #3; otherwise start service using following command:
# service snmpd start Make sure snmpd service starts automatically, when linux comes us (add snmpd service):
# chkconfig --add snmpd Step # 3 : Make sure snmp server configured properly
Run snmpwalk utility to request for tree of information about network entity. In simple words query snmp server for your IP address (assigned to eth0, eth1, lo etc):
# snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndexip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.0.3 = 2 If you can see your IP address then please proceed to step 4; else it is a time to configure snmp server as follows (by default RHEL and RH 8/9 are not configured for snmp server for security reason):
Configure SNMP
(1) Edit file /etc/snmp/snmpd.conf using text editor:
# vi /etc/snmp/snmpd.conf Change/Modify line(s) as follows:
Find following Line:
com2sec notConfigUser default public
Replace with (make sure you replace 192.168.0.0/24 replace with your network IPs) following lines:
com2sec local localhost public
com2sec mynetwork 192.168.0.0/24 public
Scroll down bit and change:
Find Lines:
group notConfigGroup v1 notConfigUser
group notConfigGroup v2c notConfigUser
Replace with:
group MyRWGroup v1 local
group MyRWGroup v2c local
group MyRWGroup usm local
group MyROGroup v1 mynetwork
group MyROGroup v2c mynetwork
group MyROGroup usm mynetwork
Again scroll down bit and locate following line:
Find line:
view systemview included system
Replace with:
view all included .1 80
Again scroll down bit and change:
Find line:
access notConfigGroup "" any noauth exact systemview none none
Replace with:
access MyROGroup "" any noauth exact all none none
access MyRWGroup "" any noauth exact all all none
Scroll down bit and change:
Find lines:
syslocation Unknown (edit /etc/snmp/snmpd.conf)syscontact Root (configure /etc/snmp/snmp.local.conf)
Replace with (make sure you supply appropriate values):
syslocation Linux (RH3_UP2), Home Linux Router.
syscontact Vivek G Gite For your convenient, here is my /etc/snmp/snmpd.conf file. Feel free to use this file. Make sure you make backup of your existing file if you use this file as it is.
Start your snmp server and test it:
(a) Make sure when linux comes up snmpd always starts:
# chkconfig snmpd on
(b) Make sure service start whenever Linux comes up (after reboot):
# service snmpd start
(c) Finally test your snmp server:
# snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex
Step # 4 : Install mrtg if not installed
Mrtg software may install during initial installation; you can verify if MRTG installed or not with following RPM command:
rpm -qa | grep mrtg If mrtg already installed please see step # 5; else use rpmfind.net to find MRTG rpm or up2date command to install MRTG software:
# up2date -v -i mrtg Fedora Linux user can use yum command as follows to install MRTG:
# yum install mrtg Step # 5 : Commands to Configure mrtg
(a) Create document root to store mrtg graphs/html pages:
# mkdir -p /var/www/html/mymrtg/ (b) Run any one of the following cfgmaker command to create mrtg configuration file:
#cfgmaker --global 'WorkDir: /var/www/html/mymrtg' --output /etc/mrtg/mymrtg.cfg public@localhost OR (make sure your FQDN resolves, in following example i'm using rh9.test.com which is my router FQDN address)
# cfgmaker --global 'WorkDir: /var/www/html/mymrtg' --output /etc/mrtg/mymrtg1.cfg public@rh9.test.com (c) Create default index page for your MRTG configuration:
# indexmaker --output=/var/www/html/mymrtg/index.html /etc/mrtg/mymrtg.cfg (d) Copy all tiny png files to your mrtg path:
# cp -av /var/www/html/mrtg/*.png /var/www/html/mymrtg/ Step # 6 First test run of mrtg
(a) Run mrtg command from command line with your configuration file:
# mrtg /etc/mrtg/mymrtg.cfg Note: You may get few warning message for first time; ignore them.
(b) Fire your favorite web browser (like FireFox :D ) and type url http://www.your.com/mymrtg/ or http://your-ip/mymrtg/
Step # 7 Create crontab entry so that mrtg graph / images get generated every 5 minutes
(a) Login as a root user or login as a mrtg user and type following command:
# crontab -e (b) Add mrtg cron job entry to configuration file (append following line to it):
*/5 * * * * /usr/bin/mrtg /etc/mrtg/mymrtg.cfg --logging /var/log/mrtg.log Save file and you are done with MRTG config issues :)
Step # 8 Block ports 161 & 162 at firewall
You do not want to give access to everyone to your snmp server for security reasons. SNMP server uses UDP 161, 162 ports for communication. Use Linux IPTABLES firewall to restrict access to SNMP server
(a) Allow outgoing SNMP server request from your Linux computer. This is useful when you query remote host/router (replace SERVER IO with your real IP):
SERVER="xxx.xxx.xxx.xxx"iptables -A OUTPUT -p udp -s $SERVER --sport 1024:65535 -d 0/0 --dport 161:162 -m state --state NEW,ESTABLISHED -j ACCEPTiptables -A INPUT -p udp -s 0/0 --sport 161:162 -d $SERVER --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT (b )Allow incoming SNMP client request via iptables. This is useful when you wish to accept queries for rest of the world (replace SERVER IP with your real IP):
SERVER="xxx.xxx.xxx.xxx"iptables -A INPUT -p udp -s 0/0 --sport 1024:65535 -d $SERVER --dport 161:162 -m state --state NEW,ESTABLISHED -j ACCEPTiptables -A OUTPUT -p udp -s $SERVER --sport 161:162 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT Pleae note that above two are just SNMP specific iptables rules. Please consult iptables(8) man page for complete information on iptables
Step # 9 Optional: Protect your MRTG graphs/html pages with password protected directory
Once again, you would like to restrict access to your MRTG reports. This can easily accomplished with Apache webserver's .htaccess file. If you are on webhosting server with control panel (such as ensim or plesk) then you can use control panel itself to create password-protected directory.
Below is process outlined to protect graphs using apache's .htaccess file and htpasswd command:
Step # 1: Create .htaccess file in /var/www/html/mymrtg/ directory (add text as follows):
vi /var/www/html/mymrtg/.htaccess Add following text to file:
AuthName "MRTG Graphs/Html restricted access"AuthType BasicAuthUserFile /var/members/.htpasswdrequire user mrtgadmin Step # 2: Create a user and password name (-c assumes first time you are using .htpasswd file):
# htpasswd -c /var/members/.htpasswd mrtgadmin 
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