Archive for the ‘Linux’ Category

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

Roll back RPM packages – CentOS/RedHat

Wouldn’t it be useful to be able to easily undo a yum/RPM change that you have just made? Well you can. By default yum/RPM do not save roll back information. This feature can easily be enabled by doing the following, however its not perfect and can use a lot of disk space as its repackaging […]

Pear – install alpha packages

Pear probably won’t let you install any alpha package by default (such as HTTP_Request2). Do this to install it quickly: pear config-set preferred_state alpha pear install HTTP_Request2 pear config-set preferred_state stable

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