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Ubuntu 10.04 Specific : How to downgrade to php 5.2 before install
As explained at http://community.aegirproject.org/installing/manual, the recommended version of PHP is 5.3, but some users may wish to use PHP 5.2 in order to host Drupal 5.x sites or to use modules which have PHP 5.3 compatibility issues. Should you choose to do so, the following documentation may be useful. What is explained here is specific to Ubuntu 10.04. It hasn't been tested on further versions, mostly because many sysadmins prefer to use the latest Long Term Support (LTS) version of Ubuntu, currently 10.04, on their production servers.
Follow this procedure :
sudo apt-get install python-software-properties
add-apt-repository ppa:txwikinger/php5.2
Create the file /etc/apt/preferences.d/php and input the following code in it :
Package: libapache2-mod-php5 Pin: version 5.2.10* Pin-Priority: 991 Package: libapache2-mod-php5filter Pin: version 5.2.10* Pin-Priority: 991 Package: php-pear Pin: version 5.2.10* Pin-Priority: 991 Package: php5 Pin: version 5.2.10* Pin-Priority: 991 Package: php5-cgi Pin: version 5.2.10* Pin-Priority: 991 Package: php5-cli Pin: version 5.2.10* Pin-Priority: 991 Package: php5-common Pin: version 5.2.10* Pin-Priority: 991 Package: php5-curl Pin: version 5.2.10* Pin-Priority: 991 Package: php5-dbg Pin: version 5.2.10* Pin-Priority: 991 Package: php5-dev Pin: version 5.2.10* Pin-Priority: 991 Package: php5-gd Pin: version 5.2.10* Pin-Priority: 991 Package: php5-gmp Pin: version 5.2.10* Pin-Priority: 991 Package: php5-ldap Pin: version 5.2.10* Pin-Priority: 991 Package: php5-mhash Pin: version 5.2.10* Pin-Priority: 991 Package: php5-mysql Pin: version 5.2.10* Pin-Priority: 991 Package: php5-odbc Pin: version 5.2.10* Pin-Priority: 991 Package: php5-pgsql Pin: version 5.2.10* Pin-Priority: 991 Package: php5-pspell Pin: version 5.2.10* Pin-Priority: 991 Package: php5-recode Pin: version 5.2.10* Pin-Priority: 991 Package: php5-snmp Pin: version 5.2.10* Pin-Priority: 991 Package: php5-sqlite Pin: version 5.2.10* Pin-Priority: 991 Package: php5-sybase Pin: version 5.2.10* Pin-Priority: 991 Package: php5-tidy Pin: version 5.2.10* Pin-Priority: 991 Package: php5-xmlrpc Pin: version 5.2.10* Pin-Priority: 991 Package: php5-xsl Pin: version 5.2.10* Pin-Priority: 991 Package: php5-mcrypt Pin: version 5.2.6* Pin-Priority: 991 Package: php5-imap Pin: version 5.2.6* Pin-Priority: 991
Then proceed Aegir install as explained at http://community.aegirproject.org/installing/debian