While Firefox is closed, backup the places.sqlite file in your profile folder. If found, also backup places.sqlite-shm and places.sqlite-wal

• Profiles - Where Firefox stores your bookmarks, passwords and other user data

See also:

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

• History Export: https://addons.mozilla.org/firefox/addon/history-export/

so if i install a new OS, i just backup the places.sqlite and places.sqlite-shm and places.sqlite-wal only and after instillation back these files?

Thank you

You need to create a backup copy of the places.sqlite file before installing the new operating system. In short, it goes like this:

1. Locate your profile folder.
2. Quit Firefox.
3. Create a backup copy of the places.sqlite file in a safe location that won't be affected by the operating system upgrade (like a removable Flash drive).
4. Upgrade your operating system.
5. Locate your profile folder. Depending on how you've performed the upgrade, you might find that your old profile folder has been preserved, along with all the data in it, and restoring the backup is not necessary.
6. Quit Firefox.
7. Replace the current places.sqlite file with the backup you created earlier.

places.sqlite-shm and places.sqlite-wal are temporary files that should only exist while Firefox is running. If you can't find them while Firefox is closed, it's a good thing.