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Gluster active/passive cluster

Gluster is a nice distributed file system which offers some management benefits over block level storage systems like DRBD. By design Gluster works in an active/active cluster configuration, however for applications where millisecond precision data replication is essential, an active/passive configuration is preferable. This is how (based on SLES11 with HAE): usual SLES HA cluster […]

Load Balanced Linux Web Cluster

Another example of a load balanced apache cluster, this time active-active using Pacemaker/Corosync/ldirectord. This example is using CentOS. 10.11.1.40 – fixed IP of server1 10.11.1.41 – fixed IP of server 2 10.11.1.80 – apache site 1 (virtual IP) 10.11.1.50 – apache site 1 server 1 10.11.1.51 – apache site 1 server 2 10.11.1.90 – apache […]

High Availability Linux Web Server Example

Just a quick example of setting up a Linux HA failover environment for an Apache/MySQL web server. This runs through a Ubuntu installation, however RedHat shouldn’t vary too much. 2.11.1.24 – fixed IP of server1 2.11.1.25 – fixed IP of server2 2.11.1.30 – apache site1 (virtual IP) 2.11.1.31 – apache site2 (virtual IP) Make sure […]

Android Apps for a System Administrator

With phones getting smarter and smarter, its now possible to monitor servers and perform basic administration tasks from your android handset. Here are a few tools I find useful. Connectbot is a great SSH client for the Android. It is fully functional, supporting SSH keys and copy/paste etc.   For Windows RDP connections, I found […]

Screen – Can be useful!

Screen is something I’ve never been interested in using previously, but to be honest, it has many benefits. Screen is basically a window manager that allows you to run many windows from your SSH session. By doing this you don’t need to initiate several SSH sessions to a box when running complex tasks. Also if […]

Install Java 1.6 JRE and JDK On CentOS5

Very busy right now, so here’s a quick and dirty writeup for install Java 1.6 on centos5. To install the JDK yum install -y jpackage-utils wget http://cds.sun.com/is-bin/INTERSHOP.enfinity/WFS/CDS-CDS_Developer-Site/en_US/-/USD/VerifyItem-Start/jdk-6u14-linux-x64-rpm.bin?BundledLineItemUUID=KxWJ_hCuwSUAAAEvTWRZB8TT&OrderID=WeuJ_hCuedUAAAEvLGRZB8TT&ProductID=tPxIBe.oz2IAAAEhmh0zLjfT&FileName=/jdk-6u14-linux-x64-rpm.bin chmod +x jdk-6u14-linux-i586-rpm.bin ./jdk-6u14-linux-i586-rpm.bin

Configuring TFTP on Centos to backup Cisco ASA / IOS

Setting up TFTP on CentOS is actually very trivial (excuse the pun)! I find it useful for backing up config from network devices such as my Cisco ASA. Install tftp: yum install tftp-server chkconfig tftp on service xinetd restart

crontab format

1 2 3 4 5 /path/to/command arg1 arg2 Where: * 1: Minute (0-59) * 2: Hours (0-23) * 3: Day (0-31) * 4: Month (0-12 [12 == December]) * 5: Day of the week(0-7 [7 or 0 == sunday]) * /path/to/command – Script or command name to schedule crontab -e = edit crontab -l = […]

screen on Linux

After installing screen you can have multiple sessions per ssh connection and they can be resumed if the connection is lost. type screen to start Now open a new window with “Ctrl-A” “c” You can create several windows and toggle through them with “Ctrl-A” “n” for the next window or “Ctrl-A” “p” for the previous […]

Configuring a samba server

install samba via yum etc. Create the smb.conf config file in /usr/local/samba/lib/smb.conf Basic smb.conf sample: [global] workgroup = DEVELOPMENT encrypt passwords = yes [homes] guest ok = no read only = no browseable = no