After upgrading apt I still got the GUI prompt over and over, and /var/lib/update-notifier/package-data-downloads/partial was found empty. However, I removed and installed ttf-mscorefonts-installer and while I didn't get any failed to fetch errors, and still got the: W: Can't drop privileges for downloading as file 'FILE' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) The fonts installed without errors as per below. Hence, my root cause issue seems to have been I didn't go through a remove/install cycle of ttf-mscorefonts-installer. sudo apt install ttf-mscorefonts-installer Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: ttf-mscorefonts-installer 0 upgraded, 1 newly installed, 0 to remove and 2 not upgraded. Need to get 29.5 kB of archives. After this operation, 134 kB of additional disk space will be used. Get:1 http://us.archive.ubuntu.com/ubuntu xenial/multiverse amd64 ttf-mscorefonts-installer all 3.4+nmu1ubuntu2 [29.5 kB] Fetched 29.5 kB in 0s (93.8 kB/s) Preconfiguring packages ... Selecting previously unselected package ttf-mscorefonts-installer. (Reading database ... 281292 files and directories currently installed.) Preparing to unpack .../ttf-mscorefonts-installer_3.4+nmu1ubuntu2_all.deb ... mscorefonts-eula license has already been accepted Unpacking ttf-mscorefonts-installer (3.4+nmu1ubuntu2) ... Processing triggers for fontconfig (2.11.94-0ubuntu1.1) ... Processing triggers for update-notifier-common (3.168.3) ... ttf-mscorefonts-installer: processing... ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/andale32.exe Get:1 http://downloads.sourceforge.net/corefonts/andale32.exe [198 kB] Fetched 198 kB in 10s (18.2 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/andale32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/arial32.exe Get:1 http://downloads.sourceforge.net/corefonts/arial32.exe [554 kB] Fetched 554 kB in 3s (145 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/arial32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/arialb32.exe Get:1 http://downloads.sourceforge.net/corefonts/arialb32.exe [168 kB] Fetched 168 kB in 7s (22.2 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/arialb32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/comic32.exe Get:1 http://downloads.sourceforge.net/corefonts/comic32.exe [246 kB] Fetched 246 kB in 3s (79.0 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/comic32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/courie32.exe Get:1 http://downloads.sourceforge.net/corefonts/courie32.exe [646 kB] Fetched 646 kB in 10s (63.7 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/courie32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/georgi32.exe Get:1 http://downloads.sourceforge.net/corefonts/georgi32.exe [392 kB] Fetched 392 kB in 1s (230 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/georgi32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/impact32.exe Get:1 http://downloads.sourceforge.net/corefonts/impact32.exe [173 kB] Fetched 173 kB in 1s (127 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/impact32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/times32.exe Get:1 http://downloads.sourceforge.net/corefonts/times32.exe [662 kB] Fetched 662 kB in 5s (118 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/times32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/trebuc32.exe Get:1 http://downloads.sourceforge.net/corefonts/trebuc32.exe [357 kB] Fetched 357 kB in 3s (102 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/trebuc32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/verdan32.exe Get:1 http://downloads.sourceforge.net/corefonts/verdan32.exe [352 kB] Fetched 352 kB in 2s (120 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/verdan32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/webdin32.exe Get:1 http://downloads.sourceforge.net/corefonts/webdin32.exe [185 kB] Fetched 185 kB in 2s (92.4 kB/s) W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/webdin32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) These fonts were provided by Microsoft "in the interest of cross- platform compatibility". This is no longer the case, but they are still available from third parties. You are free to download these fonts and use them for your own use, but you may not redistribute them in modified form, including changes to the file name or packaging format. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/andale32.exe extracting fontinst.inf extracting andale.inf extracting fontinst.exe extracting AndaleMo.TTF extracting ADVPACK.DLL extracting W95INF32.DLL extracting W95INF16.DLL All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/arial32.exe extracting FONTINST.EXE extracting fontinst.inf extracting Ariali.TTF extracting Arialbd.TTF extracting Arialbi.TTF extracting Arial.TTF All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/arialb32.exe extracting fontinst.exe extracting fontinst.inf extracting AriBlk.TTF All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/comic32.exe extracting fontinst.inf extracting Comicbd.TTF extracting Comic.TTF extracting fontinst.exe All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/courie32.exe extracting cour.ttf extracting courbd.ttf extracting courbi.ttf extracting fontinst.inf extracting couri.ttf extracting fontinst.exe All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/georgi32.exe extracting fontinst.inf extracting Georgiaz.TTF extracting Georgiab.TTF extracting Georgiai.TTF extracting Georgia.TTF extracting fontinst.exe All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/impact32.exe extracting fontinst.exe extracting Impact.TTF extracting fontinst.inf All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/times32.exe extracting fontinst.inf extracting Times.TTF extracting Timesbd.TTF extracting Timesbi.TTF extracting Timesi.TTF extracting FONTINST.EXE All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/trebuc32.exe extracting FONTINST.EXE extracting trebuc.ttf extracting Trebucbd.ttf extracting trebucbi.ttf extracting trebucit.ttf extracting fontinst.inf All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/verdan32.exe extracting fontinst.exe extracting fontinst.inf extracting Verdanab.TTF extracting Verdanai.TTF extracting Verdanaz.TTF extracting Verdana.TTF All done, no errors. Extracting cabinet: /var/lib/update-notifier/package-data-downloads/partial/webdin32.exe extracting fontinst.exe extracting Webdings.TTF extracting fontinst.inf extracting Licen.TXT All done, no errors. All fonts downloaded and installed. Setting up ttf-mscorefonts-installer (3.4+nmu1ubuntu2) ...