I messed up my biblatex installation by attempting to manually upgrade it.
Right now, basic commands like \textcite cause an Undefined control sequence error.
As a user of Ubuntu 16.04, TeX Life was either preinstalled or I installed it with apt some time ago.
Now, I wanted to upgrade biblatex (to use a feature introduced in version 3.3), and thus downloaded version 3.7 from sourceforge.
Following the instructions in the README, I used the .tds.tgz archive and placed the under texmf tree.
While writing this post, I realise that I put the files in the wrong place: I put them into /usr/share/texlive/texmf/, while the instructions say /usr/share/texmf-local/ (which doesn't exist) or /usr/local/share/texmf/ (which is empty but for the single file ls-R).
So, I probably should have used one of the local ones, creating missing intermediate directories (would that have worked while keeping TeX Live as it is?).
What is the best way to recover from this situation? Should I remove all of TeX Live through the package manager and reinstall it? Or can I manually undo the replacements using some TeX Live repository?
biblatex3.7/Biber 2.7. You will always need matching versions ofbiblatexand Biber. If you want an up-to-date system you could look at installing vanilla TeX live (see here). But before you do anything else, try what Ulrike suggested, maybe you are lucky and it is indeed only the temporary files that cause trouble here. – moewe Aug 07 '17 at 11:06biberto version 2.7 (it seemed to have worked) and I had recompiled from scratch. I left that all out to keep the post focused. – lenz Aug 07 '17 at 11:32aptrepositories, but from tug.org. On this site this is sometimes referred to as a vanilla install. See How to install “vanilla” TeXLive on Debian or Ubuntu?. In a way it is only 'vanilla' in so far that you get it from TUG directly and not via your distribution or another middle man. – moewe Aug 07 '17 at 11:39