This one is a little embarrassing.
Just trying to install Magento on a new (fresh) container. Running across the following style of error (when executing ./pear install magento-core/Mage_All_Latest-stable) :
Starting to download Lib_ZF_Locale-220.127.116.11.tgz (1,279,370 bytes) ...done: 1,279,370 bytes install ok: channel://connect.magentocommerce.com/core/Lib_ZF_Locale-18.104.22.168 Notice: Undefined variable: php_errormsg in Installer.php on line 566 PHP Notice: Undefined variable: php_errormsg in /home/complex/www/magento/downloader/pearlib/php/PEAR/Installer.php on line 566 ERROR: failed to write ./lib/Zend/Pdf/Element/.tmpObject.php: install ok: channel://connect.magentocommerce.com/core/Lib_Varien-22.214.171.124 ERROR: unable to unpack ./downloader/pearlib/download/Mage_Core_Modules-126.96.36.199.tgz ERROR: unable to unpack ./downloader/pearlib/download/Mage_Core_Adminhtml-188.8.131.52.tgz
Turns out that the default Quota for the OpenVZ container I had was extremely small. Magento (or pear) doesn't complain about disk space explicitly...
In the host /etc/vz/vz.conf, all I had to do was adjust the :
# Disk quota parameters #DISK_QUOTA=yes DISK_QUOTA=no
and then run (in the Magento container) :
cd magento # This is the base directory of the Magento installation rm -rf downloader/pearlib/cache/* downloader/pearlib/download/* ./pear mage-setup . ./pear install magento-core/Mage_All_Latest-stable