Add the X2Go repo to your yum configuration.

Check that you have activated the “optional” channel:

$ sudo rhn-channel -l

If the optional channel for your base channel is not active, activate it. e.g.:

$ sudo rhn-channel --add -c rhel-x86_64-server-optional-6

Currently, even in the optional channel, there is no official package for sshfs and it is not (yet?) included in the x2go repo. Thus it has to be downloaded form an alternate source:

$ sudo yum install fuse fuse-libs
$ wget http://pkgs.repoforge.org/fuse-sshfs/fuse-sshfs-2.2-1.el6.rf.x86_64.rpm
$ sudo rpm -i --nosignature fuse-sshfs-2.2-1.el6.rf.x86_64.rpm

URL to most recent EPEL repo installation package available here

$ wget http://mirror01.th.ifl.net/epel/6/i386/epel-release-6-7.noarch.rpm
$ sudo rpm -i epel-release-6-7.noarch.rpm
$ sudo yum install fuse-sshfs

You should now be able to install the x2goserver package:

$ sudo yum install x2goserver