How to integrate KeePass2 and Firefox using Kee in Ubuntu 18.04 - 20.04?

I have already Installed KeePass2 and also installed both Add-ons Kee. But I don't know how to integrate it.

How can I accomplish this?

Ubuntu 14.04, 15.10 / Linux Mint 17

First, you neither need PassIFox nor the extra PPA describe by @Faisal Haq Salafi as mono-complete and keepass2 are already available in the repository.

Installation

1. Download & Install KeeFox add-ons

2. install keepass2 and mono CLI compiler and system manager library:

   sudo apt-get install keepass2 mono-dmcs libmono-system-management4.0-cil libmono-system-numerics4.0-cil
   

   • upvote Faisal Haq Salafi for answer basis;
   • upvote Simounet for narrowing down the package list (6Mo vs. 125Mo with mono-complete);

Configuration

• KeePass plugin location: /usr/lib/keepass2/plugins

• Keefox

  • KeePass installation location: /usr/lib/keepass2
  • Mono executable location: /usr/bin/mono

KeePassRPC plugin

# create a plugins sub-directory in keepass2 directory
sudo sh -c 'mkdir /usr/lib/keepass2/plugins' 
# copy the keefox plugin into it
sudo ln --force --no-dereference --symbolic $HOME/.mozilla/firefox/*.default/extensions/[email protected]/deps/KeePassRPC.plgx /usr/lib/keepass2/plugins/

Restart

Quit and restart both:

1. Keepass2, then unlock your vault;
2. Firefox, check keefox icon for information

Ubuntu > 18.04 - 20.04
Install KeyPass2:

Press Alt+Ctrl+T to start terminal and run following commands one by one.

sudo apt-add-repository ppa:jtaylor/keepass  
sudo apt-get update  
sudo apt-get install keepass2 mono-complete

Open Firefox, install Kee from Add-on

Tools>Add-ons

Search for Kee and install it.

Open as Administrator (Access), skip if you have it, if not follow the step.

sudo apt install nautilus-admin
nautilus -q

Download KeePassRPC plugins
KeePassRPC.plgx

Right click plugins (/usr/lib/keepass2/plugins) folder select
"Open as Administrator"

Copy Paste the latest version of KeePassRPC into the plugins folder

/usr/lib/keepass2/plugins  

You're all done!

[Edited on 04/29/2016]

Since the 1.6.0 version of KeeFox, this trick is not working. New libs are required. At the moment, I found libmono2.0-cil but there is more. I posted a topic on the the KeeFox forum.

[Original post]

KeeFox don't need everything from mono, so it's useless to install mono-complete. mono-dmcs and libmono-system-management4.0-cil must be enough. So, this command must do the trick:

sudo apt-get install keepass2 mono-dmcs libmono-system-management4.0-cil

With this method, you'll spare more than 120Mo and a bunch of useless lib to keep up to date. I get this requirement from the KeeFox GitHub wiki: https://github.com/luckyrat/KeeFox/wiki/en-|-Running-KeeFox-under-Mono