Or you can import the clearos 5f17cd5a PGP key:

-----BEGIN PGP PUBLIC KEY BLOCK-----

Version: GnuPG v1.2.6 (GNU/Linux)



mQGiBEqUXAoRBACrf5fc6j5AdF0cdPSeLXxm8m9smx1qoBRN89IZu+XX236C/L69

psawagHaxaeNURoPml4RBQakendR7pB+CctygJY8D9WYw5ti0kG+7jn7d/06PcOd

ULKMhrFNmppvPZ7J5wE7jAviO6cEWpjiBnDU1pBz+/k3DF0tgATDos54AwCg/PaO

zWm38wQ4ZCThBBe5VXCpR+sEAIelP2Hf6FLhgU6fuw+RnqG2qI70YpXGz1OYDX5c

rgGEiBatXpdIMdcHA9godrHCC01LSkrPefHtL/mtktems+A/iPdMwr7GN7rHiDoK

MdCbGFCQ8q9EJyGXgh69oUi5i6sp7xqpi8YO1oMMcUWdIDEwNExBjGwdyqelblH2

A9bQA/4kj//VlGFxFbbI11ORlfpBHy/nK9M5lPlUIKRp58X8Zxykq6LU0UQJeRpd

aK859Kl0IhaLewcsZ2XNM/USlM0j0Z1vSifmrflfw8UiWIhg9kwFKdPq404K2BOH

0XU1Pko1UCKJMFBggDt1eagEt6q/s2fqvcAAlDdHDdUygIJ2bbQtQ2xlYXJPUyBL

ZXkgPGNsZWFyb3Mta2V5QGNsZWFyZm91bmRhdGlvbi5jb20+iF4EExECAB4FAkqU

XAoCGwMGCwkIBwMCAxUCAwMWAgECHgECF4AACgkQQkLQ4F8XzVreXQCgwxwuxbxl

2Iq+QxFiDbORyEHOoawAn1oHuU56jSa1iOeKGXoi2MyNj18quQENBEqUXAoQBACl

3Rrq7iundTmhKU3uCM4ukaLXp3wBcY8pqLWQClOfgy4u6xhsjWG9lCqmoxojwUcV

M2y409kzAUmuWc2/d7X/fuVQigNx27RgWev95ulV8d4eRBSyT4bDyZ5y/4/1UFp/

ZNer11WK/1Xt+qFVnRtVwLyi8kCs9NutrkdmWU4m+wADBQP+IdrkiIDwfSa7wf5K

6xpZW3Us1MU+EMLsIfc0wAUYY7CeYlLTEPhn+4gY6z3axH6RFB0vVJ3ZLsDHM4zd

dItWbIVUqnre7Xo8LYnRCs2O5y8E/s9fZCkLQ1vJ/jTke5Fb9Cah3ZX0fU9ONNat

+Otk9z9e3kD2HvcdPpWzQcN+KsWISQQYEQIACQUCSpRcCgIbDAAKCRBCQtDgXxfN

Wkn5AKCNH729iHeI2T05GbyJTUX9an2hvgCfeqeP9EGLVkyA0okYhp7R1pm8SYI=

=L4OU

-----END PGP PUBLIC KEY BLOCK-----

I lost 1 hour to look for this key in the web without success. Finally log in to ClearOS 5.2 and key was inside
Put contents in file (original name was clearos-gpg-key) and use command rpm --import "name of file"
More information Checking a Package's Signature

Glad it is working. Perhaps downloading the rpm locally then (re)intalssing it with "yum localinstall --nogpgcheck ...." may have got round the signature problem as well.

o.k. - here we go:

rpm2cpio /mnt/shares/library/Linux/ClearOS\ 6.5/nss-softokn-freebl-3.14.3-19.el6_6.x86_64.rpm | cpio -idmv
rpm2cpio /mnt/shares/library/Linux/ClearOS\ 6.5/nss-softokn-3.14.3-19.el6_6.x86_64.rpm | cpio -idmvu

solved the Signature key problem

and next:

rpm -ivh --force --nodeps clearos-release-community-6-6.6.0.2.v6.noarch.rpm

did solved my $releaseserver issue:

python -c 'import yum, pprint; yb = yum.YumBase(); pprint.pprint(yb.conf.yumvar, width=1)'
Loaded plugins: clearcenter-marketplace, fastestmirror
{'arch': 'amd64',
'basearch': 'x86_64',
'releasever': '6',

Hope - everything is up and fine now

THX, but I not able to install any package because of the rpm signature problem:

rpm -Uvh --force http://mirror.clearfoundation.com/clearos/community/6.4.0/updates-testing/x86_64/RPMS/clearos-release-community-6-6.6.0.1.v6.noarch.rpm
Retrieving http://mirror.clearfoundation.com/clearos/community/6.4.0/updates-testing/x86_64/RPMS/clearos-release-community-6-6.6.0.1.v6.noarch.rpm
error: /var/tmp/rpm-tmp.WpB1Qu: Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: /var/tmp/rpm-tmp.WpB1Qu cannot be installed

Reading this and following it through suggests it comes from /etc/redhat-release. This is a symlink to /etc/clearos-release. /etc/system-release also symlinks to here. Mine contains:

ClearOS Community release 6.5.0 (Final)

Looking at the clearos-updates-testing repo packages clearos-release-community-6-6.6.0.???.v6.noarch.rpm it looks like this should contain something like:

ClearOS Community release 6.6.0 Beta (Beta 1)

or

ClearOS Community release 6.6.0 Beta (Beta 2)

and will probably upgrade to

ClearOS Community release 6.6.0 (Final)

Have a play, but it is at your risk.

[edit]
You may even be able to fix it with a:

rpm -Uvh --force http://mirror.clearfoundation.com/clearos/community/6.4.0/updates-testing/x86_64/RPMS/clearos-release-community-6-6.6.0.1.v6.noarch.rpm

[/edit]

I got that nss-softokn and nss-softokn-freebln problem fixed, but the variable $releaseserver is now not set anymore:
yum version nogroups
Loaded plugins: clearcenter-marketplace, fastestmirror
Warning: RPMDB altered outside of yum.
Installed: $releasever/x86_64

Doing rpm for package nss-softokn-freebl get package not installed:

rpm -q nss-softokn-freebl
error: rpmdbNextIterator: skipping h# 1176 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
package nss-softokn-freebl is not installed

well ... a bunch of these lines:
error: rpmdbNextIterator: skipping h# 207 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 725 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 986 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 733 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 223 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 994 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 741 Header V4 DSA/SHA1 Signature, key ID 66534c2b: BAD
error: rpmdbNextIterator: skipping h# 231 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 1002 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 1010 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 757 Header V4 DSA/SHA1 Signature, key ID 66534c2b: BAD
error: rpmdbNextIterator: skipping h# 247 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 1018 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 508 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD
error: rpmdbNextIterator: skipping h# 765 Header V4 DSA/SHA1 Signature, key ID 5f17cd5a: BAD

OK - unfortunately it looks like it is related to this upstream packaging bug in nss-softokn
http://www.clearfoundation.com/component/option,com_kunena/Itemid,232/catid,39/func,view/id,67784/

What's the output of 'rpm -qa | grep nss-softokn'?

No, it is not. Regardless witch package I try to install I get alleyways that error since last possible update on 01/19/15.

Latest update list from yum.log:
Jan 19 16:05:27 Updated: glibc-2.12-1.149.el6_6.4.x86_64
Jan 19 16:05:39 Updated: glibc-common-2.12-1.149.el6_6.4.x86_64
Jan 19 16:05:43 Updated: glibc-headers-2.12-1.149.el6_6.4.x86_64
Jan 19 16:05:44 Updated: glibc-devel-2.12-1.149.el6_6.4.x86_64
Jan 19 16:05:45 Updated: nscd-2.12-1.149.el6_6.4.x86_64
Jan 19 16:06:22 Updated: gdbm-1.8.0-37.el6.x86_64
Jan 19 16:06:23 Updated: gdbm-devel-1.8.0-37.el6.x86_64
Jan 19 16:07:18 Updated: nss-softokn-3.14.3-19.el6_6.x86_64

Is it a specific RPM every time?