Building a Two-Node Linux Cluster with Heartbeat
According to the accompanying documentation, you need to install a second NIC on both nodes and connect them with a cross overcable. Besides the second NIC, a null modem cable connecting the serial (com) ports of each node is mandatory (according to the documentation). I followed the instructions in the documentation and installed everything. However, as I did more tests on the cluster, I found that the null modem cable, crossover cable and the second NIC are optional; they are nice to have but definitely not mandatory.
Configuring Heartbeat is the most important part of the whole installation and must be set up correctly to get your cluster working. Moreover, it should be identical on both nodes. There are three configuration files, all stored under /etc/ha.d: ha.cf, haresource and aythkeys.
debugfile /var/log/ha-debug # # File to write other messages to # logfile /var/log/ha-log # # Facility to use for syslog()/logger # logfacility local0 # # keepalive: how many seconds between heartbeats # keepalive 2 # # deadtime: seconds-to-declare-host-dead # deadtime 10 udpport 694 # # What interfaces to heartbeat over? # udp eth0 # node atm1 node cluster1 # # ------> end of ha.cf
Whatever is not shown above, you can simply leave as it was (all commented out by the #). The last three options are most important:
udp eth0 # node atm1 node cluster1
Unless you have a cross cable, you should use your eth0 (your only NIC) for udp; the two nodes at the end of the above files must be the same as returned by uname -n from each node.
atm1 IPaddr::192.168.1.4 httpd smb dhcpd
This is the only line you need; in the above example, I included httpd, smb and dhcpd. You may add as many dæmons as you want, provided they have the exact same spelling as those dæmons under /etc/rc.d/init.d
You don't need to add anything to this file, but you have to issue the command
chmod 600 /etc/ha.d/authkeys
You may start the dæmon with
service heartbeat start
Once heartbeat is started on both nodes, you will find that the ifconfig from the primary server will return something like:
node1 ifconfig for node1 eth0 Link encap:Ethernet HWaddr 00:60:97:9C:52:28 inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:18617 errors:0 dropped:0 overruns:0 frame:0 TX packets:14682 errors:0 dropped:0 overruns:0 carrier:0 collisions:3 txqueuelen:100 Interrupt:10 Base address:0x6800 eth0:0 Link encap:Ethernet HWaddr 00:60:97:9C:52:28 inet addr:192.168.1.4 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Interrupt:10 Base address:0x6800 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:3924 Metric:1 RX packets:38 errors:0 dropped:0 overruns:0 frame:0 TX packets:38 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0
When you see the line eth0:0, heartbeat is working, and you can try to access the server by using http://192.168.1.4 and check the log files /var/log/ha-log. Also, check the log file on node2 (192.168.1.3) and try
ps -A | grep dhcpd
and you should find no running dhcpd on node2.
Now, the real HA test. Reboot, and then shut down the primary server (node1: 192.168.1.2). Don't just power down the server; make sure you issue reboot or press CTL-ALT-DEL and wait until everything is shut down properly before you turn off your PC.
Within ten seconds, go to node2 and try ifconfig. If you can get the IP aliasing eth0:0, you are in business and have a working HA two-node cluster.
eth0 Link encap:Ethernet HWaddr 00:60:08:26:B2:A4 inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:15673 errors:0 dropped:0 overruns:0 frame:0 TX packets:17550 errors:0 dropped:0 overruns:0 carrier:0 collisions:2 txqueuelen:100 Interrupt:10 Base address:0x6700 eth0:0 Link encap:Ethernet HWaddr 00:60:08:26:B2:A4 inet addr:192.168.1.4 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:15673 errors:0 dropped:0 overruns:0 frame:0 TX packets:17550 errors:0 dropped:0 overruns:0 carrier:0 collisions:2 txqueuelen:100 Interrupt:10 Base address:0x6700
You can try
ps -A | grep dhcpd
or you can try to release and renew the IP info on your Win9x workstation, and you should see the new address for the dhcpd server.
|PostgreSQL, the NoSQL Database||Jan 29, 2015|
|HPC Cluster Grant Accepting Applications!||Jan 28, 2015|
|Sharing Admin Privileges for Many Hosts Securely||Jan 28, 2015|
|Red Hat Enterprise Linux 7.1 beta available on IBM Power Platform||Jan 23, 2015|
|Designing with Linux||Jan 22, 2015|
|Wondershaper—QOS in a Pinch||Jan 21, 2015|
- PostgreSQL, the NoSQL Database
- Sharing Admin Privileges for Many Hosts Securely
- HPC Cluster Grant Accepting Applications!
- Designing with Linux
- Wondershaper—QOS in a Pinch
- Internet of Things Blows Away CES, and it May Be Hunting for YOU Next
- January 2015 Issue of Linux Journal: Security
- Ideal Backups with zbackup
- Red Hat Enterprise Linux 7.1 beta available on IBM Power Platform
- Slow System? iotop Is Your Friend
Editorial Advisory Panel
Thank you to our 2014 Editorial Advisors!
- Jeff Parent
- Brad Baillio
- Nick Baronian
- Steve Case
- Chadalavada Kalyana
- Caleb Cullen
- Keir Davis
- Michael Eager
- Nick Faltys
- Dennis Frey
- Philip Jacob
- Jay Kruizenga
- Steve Marquez
- Dave McAllister
- Craig Oda
- Mike Roberts
- Chris Stark
- Patrick Swartz
- David Lynch
- Alicia Gibb
- Thomas Quinlan
- Carson McDonald
- Kristen Shoemaker
- Charnell Luchich
- James Walker
- Victor Gregorio
- Hari Boukis
- Brian Conner
- David Lane