Apache throwing 403 on serving images from an NFS share

Finally resolved this. It had been an SELinux issue all along. Found the solution here - http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/selinux-guide/rhlcommon-section-0068.html

In Red Hat Enterprise Linux 4 most targeted daemons do not interact with user data and are not affected by NFS-mounted home directories. One exception is Apache HTTP. For example, CGI scripts that are on the mounted file system have the nfs_t type, which is not a type httpd_t is allowed to execute.

Setting SELinux to permissive on the relevant servers did the job for me.

NFS always causes fun things to happen like this whenever UID/GIDs aren't lined up just right.

Assuming that your webserver is running as user "apache", make sure that the permissions on the file are such that they're world-readable.

su to the apache user and cd to the directory, and try cat'ing the files.

It's most likely a permission issue. If apache isn't writing to the directory, it doesn't care if the files it's reading are on NFS or anything else.