Hi,
Thanks for you answer, that I've marked as the correct answer.
In order for me to access it, I had to first enable and get access to the command line with SSH. For that I followed the procedure for "Enable ESXi Console and SSH" in this post.
After that, the process outlined above worked sweet. It boils down to running this from the command line:
esxcfg-nas -l
which lists shares, and shows an error for 'cosmo'. Now put a line for host "cosmo" into /etc/hosts manually (I used 'vi' for that). Run
esxcfg-nas -l
again. This time no errors. Now delete the share with:
esxcfg-nas -d cosmo
Remove previous line for 'cosmo' from /etc/hosts and all is well. Now shares can be mounted from vSphere again as expected.