The pgAdmin 4 server could not be contacted error on Ubuntu 21.10

i installed pgAdmin but when i open it i get this error :

Failed to launch pgAdmin4. Error:
Error: spawn /usr/pgadmin4/venv/bin/python3 ENOENT

when i tap this command :

sudo python3 /usr/share/pgadmin4/web/pgAdmin4.py

i get

python3: can't open file '/usr/share/pgadmin4/web/pgAdmin4.py': [Errno 2] No such file or directory

then i create the missing file path as,

sudo mkdir -p /var/cache/pgadmin/sessions

and run this command again

sudo python3 /usr/share/pgadmin4/web/pgAdmin4.py

but i get the same error

1 Answer

Ran into this on Ubuntu 21.10 (impish), because I had borked my installation paths thinking pgadmin4 wasn't fully installed when it was.

The error is because it is assuming python3.8 is installed (21.10 comes with python3.9) , but it isn't, so all the symlinks and virtual env fails. But this is happening because you've installed a version of pgadmin4 that doesn't match your Ubuntu version.

garrett@garrett-external:/etc/apt/sources.list.d$ ls
deadsnakes-ubuntu-ppa-impish.list pgadmin4.list.save pgdg.list.save
pgadmin4.list pgdg.list
##Looking at pgadmin4.list.save , I see I had at least tried to use
# hirsute 's repo:
garrett@garrett-external:/etc/apt/sources.list.d$ cat pgadmin4.list.save deb pgadmin4 main
##I'm thinking this is overriding the correct impish repos, so I'll
# try deleting that file, purging the installation and re-installing:
garrett@garrett-external:/etc/apt/sources.list.d$ ls deadsnakes-ubuntu-ppa-impish.list pgadmin4.list pgadmin4.list.save pgdg.list pgdg.list.save
garrett@garrett-external:/etc/apt/sources.list.d$ sudo rm pgadmin4.list.save
##double check that the pgadmin4 sources are correct...
garrett@garrett-external:/etc/apt/sources.list.d$ ls deadsnakes-ubuntu-ppa-impish.list pgadmin4.list pgdg.list pgdg.list.save
garrett@garrett-external:/etc/apt/sources.list.d$ cat pgadmin4.list deb pgadmin4 main
##^ok definitely the problem...should fix that....
garrett@garrett-external:/etc/apt/sources.list.d$ sudo sed -i 's/focal/impish/g' /etc/apt/sources.list.d/pgadmin4.list
garrett@garrett-external:/etc/apt/sources.list.d$ cat ./pgadmin4.list deb pgadmin4 main
##uninstall pgadmin4
garrett@garrett-external:/etc/apt/sources.list.d$ sudo apt purge pgadmin4
garrett@garrett-external:/etc/apt/sources.list.d$ sudo apt autoremove
##reinstall pgadmin4
garrett@garrett-external:/etc/apt/sources.list.d$ sudo apt update && sudo apt install pgadmin4
And now it works fine

EDIT: DON'T GO DOWN THE RABBIT HOLE BELOW

Workaround: Manually install python3.8 using the deadsnakes PPA and some temporary apt cache updating trickery

 #first add deadsnakes ppa... $ sudo add-apt-repository ppa:deadsnakes # Following the gist of , # update the deadsnakes ppa's app repos to look at the past 2 LTS versions $ sudo vim /etc/apt/sources.list.d/deadsnakes-ubuntu-ppa-impish.list ---> change 'deb impish main' to 'deb bionic main' , also add 'deb focal main' #Add the following rules which blacklist all packages from # the repos, and then selectively enable Python versions from the correct # locations. This can be put in any filename within the directory # /etc/apt/preferences.d/ (I named mine deadsnakes_pref)
Explanation: Prevent installing from deadsnakes repo.
Package: *
Pin: release o=LP-PPA-deadsnakes
Pin-Priority: 1
Explanation: Allow installing python 3.{6,7} from deadsnakes/focal
Package: *python3.6* *python3.7*
Pin: release o=LP-PPA-deadsnakes,n=focal
Pin-Priority: 500
Explanation: Allow installing python 3.8 from deadsnakes/bionic
Package: *python3.8*
Pin: release o=LP-PPA-deadsnakes,n=bionic
Pin-Priority: 500 ##temporarily change all your sources to bionic, so the python3.8 #dependencies will be met $ sudo sed -i 's/impish/bionic/g' /etc/apt/sources.list ## try to update the apt cache and install python3.8 . You'll get yelled # at for not having the proper key ring: ****************
W: GPG error: bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository ' bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
****************
## so following
##
## , I add the key
$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3B4FE6ACC0B21F32
# now this should work
$ sudo apt update && sudo apt install python3.8
#after we're done, don't forget to change back your sources
$ sudo sed -i 's/bionic/impish/g' /etc/apt/sources.list
$ sudo apt update
#And now pgadmin4 should work. If you want to run it from the terminal,
# add this line to your ~/.bash_aliases file: alias pgadmin4='/usr/pgadmin4/bin/pgadmin4'