Recently checked the logs of my ownCloud instance to see why the updater did not find the latest release. This yielded the following error messages:

get_headers( failed to open stream: operation failed at /htdocs/lib/private/httphelper.php#149
get_headers(): Failed to enable crypto at /htdocs/lib/private/httphelper.php#149
get_headers(): SSL: Success at /htdocs/lib/private/httphelper.php#149

Long story short, it turned out the chroot my PHP-FPM workers run in was missing a /dev/urandom device node. Without this, get_headers() is not able to initialize crypto stuff for HTTPS.

$ mknod /path/to/chroot/dev/urandom c 1 9

Credits go to this post . Although I don't understand a single word Russian, instructions were pretty clear.

I keep the chroots as minimal as possible, using nscd for name resolution to avoid runtime libraries that would require maintenance. A bit too minimal, in this case.