using locate on an encrypted partition

I both "run locate (updatedb) when I'm logged in", as mentioned above, and I keep my part of the locate database under my encrypted $HOME.

export LOCATE_PATH="$HOME/var/mlocate.db"

and then I index the files in$HOME with

updatedb -l 0 -o $HOME/var/mlocate.db -U $HOME

Now I have a complete index of $HOME but the database isn't visible unless $HOME is mounted and decrypted.

How about running updatedb when your file system is decrypted and try to match environment variables to read/write it?

After reading the man page, add two variables to your BASH RC file.

man locate
echo "export LOCATE_PATH=$HOME/var/lib/mlocate/mlocate.db:$LOCATE_PATH" >> ~/.bashrc
echo "export DBPATH=$HOME/var/lib/mlocate/mlocate.db:$DBPATH" >> ~/.bashrc

Make the directory specified above and add $username to the mlocate group.

mkdir -p ~/var/lib/mlocate/
sudo usermod -a -G mlocate $username

Log out and in again to count your user in the mlocate group and get the new environment variables. Now when you run,

updatedb -o $LOCATE_PATH

are the decrypted files in a locate database now? Or, what did you do to make it work or better?

You may also want to add updatedb to user's crontab. First run:

crontab -e

And add the following line:

0 12 * * * updatedb -o $HOME/var/locate

It's not really possible to update the database index without being logged in. You should log in and run the updatedb command.

Check your config in /etc/updatedb.conf. Remove ecryptfs from PRUNEFS and probably /home/.ecryptfs from PRUNEPATHS. Don't forget to run sudo updatedb after.