How to add encryption after installation?

You can encrypt your data after installation even though you didn’t choose to encrypt it during installation.

To encrypt your entire /home directory and, all it’s sub-directories, such as Documents, Downloads, Music, etc. read this link: how-to-encrypt-your-home-folder-after-installing-ubuntu that explains how to encrypt /home after you’ve installed Ubuntu. There are plenty of screenshots and narrative walking you through the process.

To summarize the link what you need to do is:

1. Backup your data. Although the migration process uses a working

   backup you want your own just to be safe.
   

2. Install the encryption software with `sudo apt-get install

   ecryptfs-utils cryptsetup`.
   

3. Create a temporary account with sudo privileges. In order to encrypt

   your /home directory you can't be logged on as yourself.
   

4. Login with temporary account.
5. Migrate your data from unencrypted /home directory to an encrypted

   /home directory using the command `sudo ecryptfs-migrate-home -u
   user` where "user" is your regular user name.
   

6. Please note besides encrypting /home your swap partition can also be

   encrypted for maximum protection.
   

7. DO NOT REBOOT
8. Login with your regular user name. A random passphrase can be

   generated which you need to write down if something goes wrong in  
   the future and you need to access /home folder manually.
   

Some people feel encrypting all of /home is overkill and can be too cumbersome when moving /home to another computer or different drive on the same computer. I tried encryption when I installed Ubuntu for the first time in 2014 but when I messed things up and had to reinstall Ubuntu I skipped the encryption option after reading problems other users encountered (although I never did have encryption problems).

If you don’t want to encrypt /home and all the sub-directories. You can have a single encrypted ~/.Private directory where you can keep certain files that need encryption such as “things I don’t want the NSA to know” or “wife’s surprise birthday party planning”. This is described here: EncryptedPrivateDirectory