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Asked: 2014-06-27 01:25:48 +0800 CST

I broke software updater by making python3 default

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I tried to make Python 3 the default Python version by running:

sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 10

This broke Python 2 programs, so I tried reversing the process and finally I tried:

sudo update-alternatives --install /usr/bin/python python2.7 /usr/bin/python2.7 10

which made python2.7 the default Python version but Software Updater doesn't run and running aptdcon in a terminal gives:

bash: /usr/bin/aptdcon: /usr/bin/python3: bad interpreter: No such file or directory

I tried reinstalling Python 3 but got:

Errors were encountered while processing:
 /var/cache/apt/archives/python3_3.4.0-0ubuntu2_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

How do I revert this mess?

python

1 Answers

  1. Best Answer

    I managed to solve the issue myself. The problem was the broken symlink in /usr/bin

    First I identified where python3 is. I guessed that the python3 binary would be in a similar folder as python2. So I typed ls -l /usr/bin/python.

    This gave me /usr/bin/python -> /etc/alternatives/python2.7.

    Since in /etc/alternatives/ there was no python3, I repeated the process

    ls -l /etc/alternatives/python2.7 gave

    /etc/alternatives/python2.7 -> /usr/bin/python2.7

    A simple ls /usr/bin/python3.[1-9] listed all the python binaries available. The one I was interested in was python3.4.

    Then I simply created a symlink with sudo ln -s /usr/bin/python3.4 /usr/bin/python3.

    Problem solved.

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