My apologies, I did not see this report when I created a duplicate issue (https://bugs.launchpad.net/ubuntu/+source/tex-common/+bug/1781002 Bug #1781002 ). I encountered this bug three days ago when I performed a fresh 16.04 install and then immediately upgraded to 18.04 via "do-release-upgrade -d". I will paste the info below but in summary, generating the en_DK.UTF-8 locale seems to be what was needed. The error occurred during a "do-release-upgrade -d" on a fresh v16.04 installation to bring it up to v18.04. Errors were encountered while processing: tex-common Exception during pm.DoInstall(): E:Sub-process /usr/bin/dpkg returned an error code (1) ProblemType: Package DistroRelease: Ubuntu 18.04 Package: tex-common 6.09 ProcVersionSignature: Ubuntu 4.4.0-130.156-generic 4.4.134 Uname: Linux 4.4.0-130-generic x86_64 ApportVersion: 2.20.9-0ubuntu7.2 Architecture: amd64 Date: Tue Jul 10 10:44:28 2018 ErrorMessage: installed tex-common package post-installation script subprocess returned error exit status 1 PackageArchitecture: all Python3Details: /usr/bin/python3.6, Python 3.6.5, python3-minimal, 3.6.5-3 PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1 RelatedPackageVersions: dpkg 1.19.0.5ubuntu2 apt 1.6.2 SourcePackage: tex-common Title: package tex-common 6.09 failed to install/upgrade: installed tex-common package post-installation script subprocess returned error exit status 1 UpgradeStatus: Upgraded to bionic on 2018-07-10 (0 days ago) Choices: 1: Launch a browser now C: Cancel Please choose (1/C): c Could not install the upgrades The upgrade has aborted. Your system could be in an unusable state. A recovery will run now (dpkg --configure -a). Setting up tex-common (6.09) ... locale: Cannot set LC_ALL to default locale: No such file or directory Running mktexlsr. This may take some time... done. Running updmap-sys. This may take some time... done. Running mktexlsr /var/lib/texmf ... done. Building format(s) --all. This may take some time... fmtutil failed. Output has been stored in /tmp/fmtutil.UIihIvhv Please include this file if you report a bug. dpkg: error processing package tex-common (--configure): installed tex-common package post-installation script subprocess returned error exit status 1 Errors were encountered while processing: tex-common Upgrade complete The upgrade has completed but there were errors during the upgrade process. To continue please press [ENTER] === Command detached from window (Tue Jul 10 11:42:28 2018) === === Command terminated with exit status 1 (Tue Jul 10 11:42:38 2018) === [screen is terminating] lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 18.04 LTS Release: 18.04 Codename: bionic apt-cache policy tex-common tex-common: Installed: 6.09 Candidate: 6.09 Version table: *** 6.09 500 500 http://us.archive.ubuntu.com/ubuntu bionic/main amd64 Packages 500 http://us.archive.ubuntu.com/ubuntu bionic/main i386 Packages 100 /var/lib/dpkg/status apt-get --reinstall install tex-common 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded. 1 not fully installed or removed. E: Internal Error, No file name for tex-common:amd64 apt-get install tex-common tex-common is already the newest version (6.09). 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 1 not fully installed or removed. Do you want to continue? [Y/n] y perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = "en_US:", LC_ALL = (unset), LC_TIME = "en_DK.utf8", LC_COLLATE = "C", LANG = "en_US.UTF-8" are supported and installed on your system. perl: warning: Falling back to a fallback locale ("en_US.UTF-8"). locale: Cannot set LC_ALL to default locale: No such file or directory Setting up tex-common (6.09) ... locale: Cannot set LC_ALL to default locale: No such file or directory Running mktexlsr. This may take some time... done. Running updmap-sys. This may take some time... done. Running mktexlsr /var/lib/texmf ... done. Building format(s) --all. This may take some time... fmtutil failed. Output has been stored in /tmp/fmtutil.8blia3MC Please include this file if you report a bug. dpkg: error processing package tex-common (--configure): installed tex-common package post-installation script subprocess returned error exit status 1 Errors were encountered while processing: tex-common #locale -a C C.UTF-8 POSIX en_US.utf8 edited /etc/locale.gen to uncomment en_DK.UTF-8 en_DK.UTF-8 UTF-8 ran the locale-gen command Generating locales (this might take a while)... en_DK.UTF-8... done en_US.UTF-8... done Generation complete. dpkg --configure -a Setting up tex-common (6.09) ... Running mktexlsr. This may take some time... done. Running updmap-sys. This may take some time... done. Running mktexlsr /var/lib/texmf ... done. Building format(s) --all. This may take some time... done.