If you've installed PCLinuxOS with an advanced partitioning, prepare for a painful surprise. SimplyMEPIS (up to 8.0 beta 2) doesn't let you install /usr, /var and /tmp into the partitions of your preference.
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Which means that once you've logged in, you need to enter the console (through ctrl-f1), mount the other partitions, delete their contents, cp -a /usr /your-usr-partition-mount-point, rename the other partition, edit fstab, etc. etc. etc.