Posts Tagged ‘Linux’

check_cab Nagios plugin for Hawk-I rack monitoring

If you use Sinetica Hawk-I or RacKMS to manage/monitor your datacentre cabinets, I’ve created a Nagios plugins to monitor each of the sensors (temperature/humidity etc). You can grab check_cab over at Nagios Exchange.

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. – fixed IP of server1 – fixed IP of server 2 – apache site 1 (virtual IP) – apache site 1 server 1 – apache site 1 server 2 – apache [...]

Some Munin Notes

Munin – its pretty handy for monitoring stuff over time to view trends. Some notes to get it up and running with a minimal config: Install munin on monitoring server: apt-get install munin vi /etc/munin/munin.conf Add something like: [Webservers;webserver-01] address use_node_name yes [Webservers;webserver-01] address use_node_name yes Group by something sensible, i.e server type, [...]

Some LVM Notes

A few LVM notes to jog the brain A. Steps to create the logical volume.. List the current physical volumes. In this instance, were interested in a blank 20GB SATA – /dev/sdb. You can extend a logical volume by adding additional phyical volumes later. fdisk -l Disk /dev/sda: 21.5 GB, 21474836480 bytes 255 heads, 63 [...]

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. – fixed IP of server1 – fixed IP of server2 – apache site1 (virtual IP) – apache site2 (virtual IP) Make sure [...]

Some NFS Notes

A few notes on configuring NFS on RedHat or Ubuntu The server packages to install are: Ubuntu: apt-get-install nfs-kernel-server nfs-common quota RedHat: yum install nfs-utils nfs-utils-lib quota The client Packages are: Ubuntu: apt-get install nfs-common RedHat: yum install nfs-utils nfs-utils-lib A few things to configure on the server: /etc/hosts.allow Any hosts listed here will be [...]

Example IPTables rules for a webserver

Just a quick and basic example IPTables ruleset to secure a web/mail server: # Allow outgoing traffic and disallow any passthroughs iptables -P INPUT DROP iptables -P OUTPUT ACCEPT iptables -P FORWARD DROP # Allow traffic already established to continue iptables -A INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT

Don’t be a Tw@t – Use At!

Sigh today I made a schoolboy error – making config changes to a live firewall on a remote server without giving myself any kind of safety net! Anyway, this is an example of where you should really use something like the at command to bail you out should anything go wrong: get the current system [...]

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 chmod +x jdk-6u14-linux-i586-rpm.bin ./jdk-6u14-linux-i586-rpm.bin