Preparing to unpack .../init-system-helpers_1.29ubuntu2_all.deb ...
Unpacking init-system-helpers (1.29ubuntu2) over (1.29ubuntu1) ...
Processing triggers for man-db (2.7.5-1) ...
/usr/bin/mandb: fork failed: Resource temporarily unavailable
Setting up init-system-helpers (1.29ubuntu2) ...
/var/lib/dpkg/info/init-system-helpers.postinst: 6: /var/lib/dpkg/info/init-system-helpers.postinst: Cannot fork
dpkg: error processing package init-system-helpers (--configure):
 subprocess installed post-installation script returned error exit status 2