Lifeograph is a private digital journal for Linux. It lets you easily create and manage your diaries.
Lifeograph includes a lot of features such as:
  • Encryption support (create a password protected diary)
  • Theming support
  • Wiki style formatting
  • Automatic backups
  • Linking entries
  • Spell checking
  • Tagging support

Ubuntu users can easily install this program by using this PPA:

sudo apt-add-repository ppa:dmxe/ppa 
sudo apt-get update 
sudo apt-get install lifeograph