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Active/Passive Cluster with Pacemaker, Corosync

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In this article I will explains how to set up and maintain an Active/Passive Cluster, using Pacemaker with Corosync with DRBD replication.

We have two nodes (same hardware), one active and another in passive mode. If the active node goes down, the passive one will automatically take its position and all running services.

This article was written complete for and with Debian 6-squeeze (With a lot of luck you could bring it to run on Ubuntu)

Active/Passive

1. Basic notes
Node-1:
Hostname: node-1
IP: 192.168.2.101

Node-2:
Hostname: node-2
IP: 192.168.2.102

Partitioning:
/dev/vda1 System / ext4
/dev/vda5 reserved for DRBD – empty
/dev/vda6 swap area

Cluster IP: 192.168.2.100
We need this cluster IP to reach currently active node.

This is a physical network structure of the cluster:
Structure
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Nomachine user limit

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Some days ago I found a strange user limitation for Nomachine Server – I know that it was the “free” edition. The user limitation came end of 2009 and my server without limitation running since 2008
I think I should visit sites of OpenSource/Free projects ofter

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/usr/NX/bin/nxserver --userlist
/usr/NX/bin/nxserver --userdel username

Very very dirty hack to prevent the limitation – Create a cron which runs every minute and remove all users:)

SSH aliases

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I think you now this problem, you have a lot different hosts with different ssh ports.
It takes to much time to write the full ssh commands and recognize all of your ports:

Easy solution – use aliases:

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vim .ssh/config
# Add this
Host piper
    HostName piper
    User root
    Port 1022
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ssh piper

Roundcube PHP Update conflict

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Another tricky error after Debian squeeze upgrade:
ERROR: Wrong ‘suhosin.session.encrypt’ option value. Read REQUIREMENTS section in INSTALL file or use Roundcube Installer, please!

The fix is very trivial:

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vim /etc/php5/apache2/php.ini
# Add this lines to the bottom of the config:
[suhosin]
suhosin.session.encrypt = Off

Solution for php5-fpm:

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php_admin_value[suhosin.session.encrypt] = Off

To upgrade the database style to roundcube version 0.9.0 I used a little workaround to prevent suhosin error reporting:

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php -d suhosin.session.encrypt=off -d date.timezone=Europe/Berlin bin/updatedb.sh --package=roundcube --version=0.8.2 --dir=`pwd`/SQL

Maemo be root

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After my failed android installation I try to restore my old state of my N900.

Here’s how to get root access:
1. Go to Application manager > Application catalogs -> New
2. Write maemo.org extras-testing for catalog name
3. Give web address as http://repository.maemo.org/extras-testing
4. Enter fremantle as the distribution
5. Enter free non-free for components

Now simply install rootsh from Application Manager.
Once you are done with rootsh, open a terminal.

You can now either try sudo gainroot and you will be root.