On RHEL7.4, thinlinc-tlmisc-4.8.0-5456.x86_64: # tl-umount-localdrives -vas Unmounting /var/opt/thinlinc/sessions/astrand/11.1540370850.ended/drives/tmp Unmounting /var/opt/thinlinc/sessions/astrand/11.1540371116.ended/drives/tmp This took, in total, 9 minutes.
We did some work on bug 1270 to get this timeout down to sensible levels. Not sure why it isn't working here.