Anyone coming from the “sendmail world” to postfix will notice immediately the care taken by postfix developers to make the transition as easy as possible. The same commands you would be used to, like for ex. mailq, newaliases, are working in postfix also.

The newaliases command works on postfix as expected, rebuilding the aliases database:
newaliases

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This article will explain how you can install the latest memcached daemon (including the libevent library) on a linux system. The only prerequisite for memcached is libevent so we will have to install this first.

Note: the output of the commands in this article are taken from a Debian Etch system. They should work on any recent linux distribution, but depending from your version you might need to make some changes. The versions of memcached and libevent used in this article are the latest stable one existing at the time this was written. Check the download pages bellow, and if newer versions exists you will probably want to use them. Read the rest of this entry »

Applies: apache 1.3.x / apache 2.0.x
Required apache module: -
Scope: global server configuration
Type: security

Description: How to disable the HTTP TRACE method on recent apache versions.

Most vulnerability scanners (like the popular nessus, but commercial ones also) will complain (normally as a low thread or warning level) about TRACE method being enabled on the web server tested.

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ldirectord is a daemon to monitor and administer real servers in a LVS cluster of load balanced virtual servers. ldirectord is typically used as a resource for heartbeat , but can also run standalone from the command line.

ldirectord monitors the health of the real servers by periodically running a service check (by default it will know how to check ftp|smtp|http|pop|pops|nntp|imap|imaps|ldap|https|dns|mysql|pgsql|sip) and if a real server fails to respond for the check, then the server is removed from service and will be reactivated once it comes back on line.

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This post is a follow up to the very useful articles posted by Cornelius on Yum usage. As you most certainly know by now, I am a debian/apt fan, but even so I had to work on several centos/fedora/rhel systems many times. One of the nicest features of yum I have found, is the ability to work with software groups. This has been very useful for me in several occasions where I had to clean up a wrong installation (removing a bunch of X related applications on a dedicated server for ex.). Removing several packages by hand would have been very time consuming, but so with just one command all the group (let’s say “X Window System”) can be removed, and with the dependencies also. Very cool!

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I am using on several projects memcached and on the application side the php memcached module. This can be installed as any pear/pecl module, or from source by downloading the source .tgz and running the classic phpize; ./configure; make; make install; While trying to upgrade the memcached module to the latest version available 2.1.2 I encoutered a problem, receiving an error during the compile step:
“configure: error: Cannot find php_session.h”

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My first contribution to the site will cover some basics about yum (so Debian users can skip this, sorry for that). Yum is the standard package manager of CentOS and Fedora Core. It is used for maintenance of your software on your system.
Most common tasks are installing and removing software on your system. In the background yum can update all software and – very important – can solve software dependencies automatically (a thing, the simple RPM command can’t do). Solving software dependencies means: yum knows when program A needs program B to work and will also install program B if you choose to install program A.

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Normally we will set the hostname of a system during the installation process. Many peoples don’t care about this, and don’t change the hostname even if for example this was set to something really stupid by the datacenter that installed the system (most likely they will set this to “debian” on any debian installation, etc). For me, it is important to see on each one of the ssh screens I will have open at any time a different hostname that is relevant and will give me quickly the information on what system I am logged in. Read the rest of this entry »

By default any modern Linux distributions will have IP Forwarding disabled. This is normally a good idea, as most peoples will not need IP Forwarding, but if we are setting up a Linux router/gateway or maybe a VPN server (pptp or ipsec) or just a plain dial-in server then we will need to enable forwarding. This can be done in several ways that I will present bellow.

Check if IP Forwarding is enabled

We have to query the sysctl kernel value net.ipv4.ip_forward to see if forwarding is enabled or not:
Using sysctl:

sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 0

or just checking out the value in the /proc system:

cat /proc/sys/net/ipv4/ip_forward
0

As we can see in both the above examples this was disabled (as show by the value 0). Read the rest of this entry »

When we setup an FTP server software (regardless if this is proftpd, vsftpd, etc.) we might face a dilemma: we want to restrict the access that ftp users will have (limited access to files normally in their own home directory) but also we want to allow them access to another folder that is normally in a different location (like development files for whatever work they are doing).

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