We have exactly the same problem. Plenty of disk space, running as root, no nails. On CentOS 6.
Message was edited by: scottlmoore on 1/15/14 2:33:55 PM CST
Logged in with different session and changed file permissions 2x and got past that error.
I am having the same issue. Linux Red Hat 5.10 2.6.18-371.4.1.el5 x86_64, logged in as root, copious amounts of space for /opt mount point, and the same error message. The installer does not appear to ever create the user.
installer: cannot access /opt/NAI/LinuxShield as user nails
[root@foobar McAfee]# id nails
id: nails: No such user
[root@foobar McAfee]# grep nails /etc/passwd