Error with sudo apt-get update; and Termnial won't open: Python update caused this?
I'm in a bind :-( I'm hoping somebody can help me with this.
I have (had) a perfectly good working Ubuntu 18.04 system, with python2.7.17 and python3.6.9. I wanted to upgrade my Python to 3.8, so I followed some online help. (like here: How do I install Python 3.8 in Lubuntu 18.04?, and here: Error when trying sudo apt-get update - Python related? )
I installed Python3.8.0 (from Ubuntu channels, not PPA).
I did update-alternatives --config python3 and in a moment of weakness, I also did update-alternatives --config python. Net-net, my python setup caused the Terminals to not open.
I un-did these changes. I had to manually setup the link to python2 again using: $ sudo ln -s /usr/bin/python2.7 /usr/bin/python. But the problems remain.
Problems: Currently, the Terminal still won't open, and sudo apt-get update fails. :-(
(I do have a couple of terminals already open... but I'm afraid of rebooting the system, lest the Terminals not open up)
For various reasons, I have to remain on Ubuntu 18.04, and I cannot do a re-install. How do I fix this? Any help much appreciated!! Thank you!
Current setup is below:
avtester@a3computer:~$ update-alternatives --list python
update-alternatives: error: no alternatives for python
avtester@a3computer:~$ update-alternatives --list python3
/usr/bin/python3.6
/usr/bin/python3.8
avtester@a3computer:~$
...
avtester@a3computer:~$ ls -lt /usr/bin/python*
lrwxrwxrwx 1 root root 18 Nov 19 09:33 /usr/bin/python -> /usr/bin/python2.7
lrwxrwxrwx 1 root root 25 Nov 18 23:36 /usr/bin/python3 -> /etc/alternatives/python3
-rwxr-xr-x 2 root root 4526456 Oct 8 05:12 /usr/bin/python3.6
lrwxrwxrwx 1 root root 33 Oct 8 05:12 /usr/bin/python3.6-config -> x86_64-linux-gnu-python3.6-config
-rwxr-xr-x 2 root root 4526456 Oct 8 05:12 /usr/bin/python3.6m
lrwxrwxrwx 1 root root 34 Oct 8 05:12 /usr/bin/python3.6m-config -> x86_64-linux-gnu-python3.6m-config
-rwxr-xr-x 1 root root 3628976 Sep 30 06:38 /usr/bin/python2.7
lrwxrwxrwx 1 root root 33 Sep 30 06:38 /usr/bin/python2.7-config -> x86_64-linux-gnu-python2.7-config
-rwxr-xr-x 2 root root 4456208 Apr 17 2020 /usr/bin/python3.5
-rwxr-xr-x 2 root root 4456208 Apr 17 2020 /usr/bin/python3.5m
-rwxr-xr-x 1 root root 5203488 Oct 28 2019 /usr/bin/python3.8
lrwxrwxrwx 1 root root 33 Oct 28 2019 /usr/bin/python3.8-config -> x86_64-linux-gnu-python3.8-config
lrwxrwxrwx 1 root root 16 Oct 25 2018 /usr/bin/python3-config -> python3.6-config
lrwxrwxrwx 1 root root 10 Oct 25 2018 /usr/bin/python3m -> python3.6m
lrwxrwxrwx 1 root root 17 Oct 25 2018 /usr/bin/python3m-config -> python3.6m-config
lrwxrwxrwx 1 root root 9 Apr 16 2018 /usr/bin/python2 -> python2.7
lrwxrwxrwx 1 root root 16 Apr 16 2018 /usr/bin/python2-config -> python2.7-config
lrwxrwxrwx 1 root root 16 Apr 16 2018 /usr/bin/python-config -> python2.7-config
avtester@a3computer:~$
avtester@a3computer:~$ python --version
Python 2.7.17
avtester@a3computer:~$ python3 --version
Python 3.8.0
avtester@a3computer:~$
The failure for sudo apt-get update is here:
avtester@a3computer:~$ sudo apt-get update
Hit:1 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:3 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease
Traceback (most recent call last):
File "/usr/lib/cnf-update-db", line 8, in <module>
from CommandNotFound.db.creator import DbCreator
File "/usr/lib/python3/dist-packages/CommandNotFound/db/creator.py", line 11, in <module>
import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'
Reading package lists... Done
E: Problem executing scripts APT::Update::Post-Invoke-Success 'if /usr/bin/test -w /var/lib/command-not-found/ -a -e /usr/lib/cnf-update-db; then /usr/lib/cnf-update-db > /dev/null; fi'
E: Sub-process returned an error code
avtester@a3computer:~$
UPDATE 1 and 2
Following some help (see: https://stackoverflow.com/questions/56218562/how-to-fix-modulenotfounderror-no-module-named-apt-pkg), I remapped my python3 alternatives to original python3.6 instead of the newly installed python3.8, as below:
avtester@a3computer:~$ ls -l /etc/alternatives/python3
lrwxrwxrwx 1 root root 18 Nov 18 23:36 /etc/alternatives/python3 -> /usr/bin/python3.8
avtester@a3computer:~$ sudo update-alternatives --config python3
[sudo] password for avtester:
There are 2 choices for the alternative python3 (providing /usr/bin/python3).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/bin/python3.8 2 auto mode
1 /usr/bin/python3.6 1 manual mode
2 /usr/bin/python3.8 2 manual mode
Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/bin/python3.6 to provide /usr/bin/python3 (python3) in manual mode
avtester@a3computer:~$
avtester@a3computer:~$ ls -l /etc/alternatives/python3
lrwxrwxrwx 1 root root 18 Nov 19 10:37 /etc/alternatives/python3 -> /usr/bin/python3.6
And now, I can Open Terminals, and perform sudo apt-get install.
HOWEVER, I see a very small list of updates? I'm not sure what that means.
avtester@a3computer:~$ sudo apt-get update
[sudo] password for avtester:
Hit:1 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:3 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease
Reading package lists... Done
avtester@a3computer:~$
What voodoo is this? If one updates the system python3 to a new version, why the does the system croak so badly??
for the record, please see my answer up in Update 1 and 2.
Update 1 and 2:
Following some help (see: https://stackoverflow.com/questions/56218562/how-to-fix-modulenotfounderror-no-module-named-apt-pkg), I remapped my python3 alternatives to original python3.6 instead of the newly installed python3.8, as below:
avtester@a3computer:~$ ls -l /etc/alternatives/python3
lrwxrwxrwx 1 root root 18 Nov 18 23:36 /etc/alternatives/python3 -> /usr/bin/python3.8
avtester@a3computer:~$ sudo update-alternatives --config python3
[sudo] password for avtester:
There are 2 choices for the alternative python3 (providing /usr/bin/python3).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/bin/python3.8 2 auto mode
1 /usr/bin/python3.6 1 manual mode
2 /usr/bin/python3.8 2 manual mode
Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/bin/python3.6 to provide /usr/bin/python3 (python3) in manual mode
avtester@a3computer:~$
avtester@a3computer:~$ ls -l /etc/alternatives/python3
lrwxrwxrwx 1 root root 18 Nov 19 10:37 /etc/alternatives/python3 -> /usr/bin/python3.6
Now I can open terminals, and perform sudo apt-get install,
however I see a very small list of updates? I'm not sure what that means.
avtester@a3computer:~$ sudo apt-get update
[sudo] password for avtester:
Hit:1 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:3 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:4 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease
Reading package lists... Done
avtester@a3computer:~$