Purpose of this page is to help when you need to contact VOMS Admin server but have problems. If you look for a general introduction to how to get a certificate, a VOMS membership, use those with CMSWEB and/or CRAB etc., please look in the CMS Offline Workbook at WorkBookStartingGrid#BasicGrid


My VOMS membership is OK but still I can't access CMSWEB or CRAB commands fail with a can't find username errpor

If you have problems with your certificate-to-username mapping as needed to access to CMSWEB or use CRAB you should check https://twiki.cern.ch/twiki/bin/view/CMSPublic/UsernameForCRAB and in particular https://twiki.cern.ch/twiki/bin/view/CMSPublic/UsernameForCRAB#Warning

I need to register in SiteDB

There is no such need since end of 2018. Forget about SiteDB

I tried to register in CMS VO and never got any email

Make sure to check your CERN email (or whichever email CERN has registered as your main email). CERN email: https://mmm.cern.ch If the email still cannot be found (also check junk), For issues with VOMS registration, please email to project-lcg-vo-cms-admin at cern.ch

Contacting VOMS server via the browser

Common Actions

I need to re-sign my AUP

I have a new (different !) certificate

  • different is what matters. If you renew your certificate (usually needed every year) and new one has the same DN, no action is needed
  • if you switch to a new DN becasue you decided to use a different CA or changed your name or whatever, you need the actions below
    • Important: do not create a new membership ! If you visit VOMS Admins web page using your new certificate, it will see that it does not know it and will prompt you to register as a new user. Having multiple membership for the same physical person in unfortunately possible, but tricky to properly manage, additionally, besides very very few special use cases, it is never useful and usually it only leads to confusion and errors.
    • what you should do is to add your certificate to your current membership. Then VOMS will accepts either certificate on equal grounds and you can safely stop using one as convenient for you. Later you can delete old certificates at your leisure simply to keep things tidy.

Add a new certificate to my membership

  1. make sure that you still have the old certificate (the one which VOMS knows you by) in your browser, so that you can authenticate to VOMS as a member
  2. make sure you have made the PEM files from your new certificate (see this link )
  3. go to your VOMS home page and scroll down a bit until you can select the "add new certificate" button as in the screeshot below (or use this quick link: https://lcg-voms2.cern.ch:8443/voms/cms/user/request-certificate.action )
  4. you will be directed to this page where you should upload a PEM encoded certificate (see the blue pointer)
  5. do not try to Enter a DN, CA couple, it is difficult to do it right
  6. select the usercert.pem file which you created in the first step, like this
  7. click on the (unfortunately badly named) "Request certificate" button at bottom right to request the addition of this certificate to your membership
  8. the request to add the certificate will be sent to CMS VOMS Administrators which will approve (unfortunately we do not have a way to take humans out this loop)

Common Problems

Basic help

  • The CERN CA web page at https://ca.cern.ch/ca/ has an HELP tab in which points to very useful, even browser specific, information. Look there first.

Can not open VOMS home page in my browser

there can be many reasons, here are some debugging tips. If you are an expert with little time, jump to #QuickTroubleshoot

Wrong URL

Possibly OS issues

  • if you get the message "This site can’t be reached: `lcg-voms2.cern.ch` unexpectedly closed the connection." and you are running on Windows, it is likely that your anti-virus program cut in and interfered with your connection (see also "Antivirus?" below). In that case, moving to a Linux distribution (e.g. Ubuntu) or a Mac and connecting from there is the fastest way to get going.

Browser issues

Browser kind ?

  • We recommend to use a recent version of Firefox. There is little to no experience with e.g. Safari among CMS VOMS administrators. Chrome has sometimes it's own view of what security should mean and can cause trouble. Feel free to use it, but in case of problems, first try Firefox.

Personal certificate ?

  • Make sure you have a valid personal certificate in your browser
  • If you have and expired certificate in your browser, you will get the same errors as if you have none. Always make sure that you keep the certificate in your browser up to date whenever you get a new one from your CA
  • The way to import/delete/inspect Your certificate is heavily browser (version) dependent, although e.g. Firefox and Chrome have a very similar look and fell for those things at least in recent (2020 e.g.) versions. CERN maintains up-to-date instruction in https://ca.cern.ch/ca/Help/ just look in the menu at the left of the page for your browser, e.g. for Firefox the item is called Import and export certificates using Firefox

CERN Authority root certificate ?

Security Exception ?

  • The VOMS server uses a certificate from the CERN Grid Certificate Authority (CA), and this is not "known" to the browsers by default, so sometimes you get a warning that the site is "insecure" or "untrusted" (see below). To fix this warning, you can install the CERN Grid CA's root certificate using the instructions in the links at: https://cafiles.cern.ch/cafiles/certificates/ -- this will also fix the same issue with other sites on the LHC Computing Grid.
  • Alternatively, if the page says "This Connection is Untrusted" or similar, you may try the shortcut offered at the last line of the same page, "I Understand the Risks" as in reality there is no risk to try. Click it, and from the next page select "Add Exception". The sub-page will ask you to "Confirm Security Exception". So you confirm, and you should be able to get in.

firewall ?

  • Check your firewall and http proxy settings

cookies ?

  • Clear the History, Cache and Cookies of Firefox and restart the browser

Antivirus ?

  • Beware your Antivirus. Especially when you are using Windows. We have seen cases in which an antivirus tool (usually Avast Antvirus) interferes with the browser making it impossible to securely connect to servers even if you trusted all CERN CA's as indicated above. For details and cure see this ticket . There are also reports that AWG antivirus on MacOS interferes destructively with CERN CA certificates, see https://hypernews.cern.ch/HyperNews/CMS/get/computing-tools/6139/2/1/1.html

KeyChain error (on Mac) ?

  • we had one report (Nov 2021) of the obscure error in the following screenshot, which was solved as: After some googling I found that there is a bug, first reported in 2009, that still seems to be present on my new mac. Using the command line tool as described here seemed to work for me: http://www.openradar.me/7092640


Certificate issues

  • Make sure you have imported your current personal certificate in your browser (i.e the one you want to be registered as CMS VO member)

Test page

Error messages and screenshots of common problems


  • Recent versions of Firefox print this very obscure message when simply there is no valid user (personal) certificate in the browser (see screenshot below). **Please make sure you have your (valid) certificate installed in Firefox.**

Check your certificate

  • Start from the VOMS Admin home page at https://voms2.cern.ch:8443 . While access to that page requires a proper SSL connection and a valid certificate, it does not require CMS VO memberhsip, so you can use it to separate VOMS problems from certificate/SSL problems. Click on cms Most common problems will be one of the following screenshots
No certificate (or expired certificate) in your browser (older browsers)

Voms home No Certificate
No certificate (or expired certificate) in your browser (newer versions e,g, Firefox 68 ))

Voms home No Certificate
Valid certificate not known to VOMS yet

Voms home Not Member

Check your certificate using the Certificate Info tab in VOMS page

  • You will see one of the following possibilities:
1 No valid certificate in your browser (older Firefox version)

Voms Cert Info No Certificate
2 No valid certificate in your browser (newer Firefox versions)

Voms Cert Info No Certificate
3 Valid certificate, but not known to VOMS

Voms Cert Info Not Member
4 All OK

Voms Cert Info OK

Still need help

  • It is impossible to help based on reports like "I got error" or "this link does not work".

  • If you need to report a problem to support, provide the specific and details error messages you get, possibly attaching screenshots. And describe the diagnostics steps you already took and what they produced.

The connection to voms2.cern.ch:8443 was interrupted while the page was loading

  • this is usually due to using http in place of https, see #Wrong_URL above
  • there are also cases where a simply browser restart can fix it

I get an empy page when connecting to VOMS

  • this is most likely a browser issue, se #Browser_issues above
  • it is also possible that the VOMS server was temporarely overloaded, try the other equivalent URL ( see #Wrong_URL above ) and try again after some random time. If problem persists contact support (see #Still_need_help above)

Can not open VOMS page (quick guide for experts)

  1. Make sure the personal certificate is in your browser (and please use Firefox or Chrome, other browsers are known to have issues) and that the certificate is valid:
    • From the generic part of the Firefox (similar on Chrome) follow the chain: Firefox -> Preferences ->  Advanced -> Encryption ->  View certificates  -> “Your Certificates” there, check that the certificate you want to use has a date for “Expires” which is in the future.

  1. If not, you have to get a new one from any of the Certificate Authorities (CA), for example from CERN: https://ca.cern.ch/ca/

  1. Then try again the "re-sign Grid usage rules" (see FAQ above about signing AUP)

Contacting VOMS server via the voms-proxy-init command

Your grid certificate needs to be present in two places:

  • the VOMS server, via the registration as VO member (see above)
  • the ~/.globus directory in the machine which you use to issue the voms-proxy-init command.
Most problems originate from having different certificates listed in those places, usually as a result of an incomplete attempt to update to a new certificate.

Typical error messages in those cases are:

  • cms: User unknown to this VO.
  • User credential is not valid!

You can verify what you have in ~/.globus with the command

  • openssl x509  -subject -dates -noout  -in ~/.globus/usercert.pem

You should compare the Subject it prints with what you used when registering in VOMS. If you need help in figuring out, please send the output of that command toghether with the one from voms-proxy-init -voms cms

-- AndreasPfeiffer

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng KeyChainError.png r1 manage 681.0 K 2021-11-19 - 09:37 StefanoBelforte KeyChainError
PNGpng VOMS-CertInfo-nocert.png r1 manage 47.8 K 2016-10-10 - 17:24 StefanoBelforte  
PNGpng VOMS-CertInfo-notmember.png r1 manage 69.4 K 2016-10-10 - 17:24 StefanoBelforte  
PNGpng VOMS-Certinfo-nocert-2.png r1 manage 41.3 K 2019-08-12 - 19:29 StefanoBelforte  
PNGpng VOMS-RequestCertificateButton.png r1 manage 73.8 K 2020-02-27 - 20:43 StefanoBelforte  
PNGpng VOMS-add-an-additional-certificate.png r1 manage 227.0 K 2018-02-07 - 13:56 StefanoBelforte  
PNGpng VOMS-add-certificate-1.png r1 manage 55.2 K 2018-02-07 - 14:58 StefanoBelforte  
PNGpng VOMS-add-certificate.png r1 manage 38.6 K 2018-02-07 - 14:57 StefanoBelforte  
PNGpng VOMS-certinfo-OK.png r1 manage 70.1 K 2016-10-10 - 17:24 StefanoBelforte  
PNGpng VOMS-home-newcert.png r1 manage 66.9 K 2016-10-10 - 17:35 StefanoBelforte  
PNGpng VOMS-nocert-2.png r1 manage 41.3 K 2019-08-12 - 19:37 StefanoBelforte  
PNGpng VOMS-nocert.png r1 manage 49.5 K 2016-10-10 - 17:24 StefanoBelforte  
PNGpng VOMS-upload-pem.png r1 manage 85.5 K 2018-02-07 - 14:58 StefanoBelforte  
PNGpng VOMSAdminHOME.png r1 manage 70.8 K 2016-10-10 - 17:24 StefanoBelforte  
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Topic revision: r36 - 2022-09-21 - AndreasPfeiffer
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