How to look at web pages for CRAB Server at CERN

URL's are of the form which are not accessible outside CERN

They can be easily accessed using SSH tunneling from the desktop where your browser runs

SSH tunnel can be setup in many ways. Here are two:

  • simplest way: using one ssh command, need to know the specific host name of the crab server
    • also need to remap all URL's like to things like localhost:8021/
  • most convenient way: everything is automatic, only need to have one ssh running to lxplus
    • requires some effort to setup and I know how to make it work with Firefox

Most convenient way

Main reference is:

That can be further enhanced by making the proxy kick-in only when specific URL patterns appear, so avoid to list the "non cern domains" and only use proxy for the few machines where it is really needed. Here's how I made this work for me

  • addo to .ssh/config file (create if missing) the lines indicated by IT, e.g. on my laptop I have:
LapSB:~$ cat ~/.ssh/config
Host lxplus*
   DynamicForward localhost:12345
    • I needed to add localhost: in front of 12345 to prevent my laptop from going in IPv6 mode which is not working for me
  • install FoxyProxy Standard addon for Firefox from
  • restart firefox open the addon menu and select Options, configure it to look like in the following sreenshots
    • main menu (only the Proxy tab is relevant), add a new proxy and get something like this. Make sure that Mode is set like shown next to the top of this image
      • foxyproxy-options.png

    • the setting for the new proxy are accessed e.g. by double clicking, there are three tabs:

      • General.png
      • Proxy_Details.png
      • URL_Patterns.png

    • Can add other URL Patterns to match e.g. DESY crab server host name

    • Change a few advanced settings in Firefox by typing about:config in the Firefox address bar and then network.proxy in the search box. In the page that you get change the three lines in bold below to make them as indicated (right cllick on any line to get a Reset button to revert to firefox default setting if needed)
      • Firefox_Settings.png

Simplest way

CERB hosts two crab servers

  • CRAB: for gird submissions
  • CERN: for CAF local submission

you will need to know the host name where they run, as of Sept. 2009 those are vocms58 (grid) and vocms55 (CAF). In case adapt the following instructions to proper host name.

Instructions for linux
  • you need to have an account on lxplus, in the following replace your lxplus user account name for <username>
  • in a shell window type
    • ssh <username>
  • then enter your lxplus password and complete the login
  • leave that ssh conenction open (e.g. iconize and forget) as long as you will be looking at the Crab server http pages
  • point your browser to http://localhost:8003 for the CERN CRAB Server and http://localhost:8004 for the CAF CRAB Server
  • if you only want to access one of the two servers, can put a single -L..... in the ssh command
  • you can of course use any port number (greater then 1024) you like in place of 8003/8004

Instructions for windows
There may be other ways using different SSH emulators, this is for the one I am using, e.g. Putty should also work
  • install SshClient 3.2.9, availble for free from various ftp repositories (google or e.g.
  • create a profile called e.g. CrabServer
  • edit it and configure as
    • Conenction tab: hostname,ch
    • Tunnelling tab, Outgoing (default) tab: clik on Add.., name CS, Listen Port 8003, Dest Host, Dest Port 8888
    • click on Add again and do the same with a different name and for host vocms55
    • click on OK, then use this profile to log on lxplus and leave the conenction open
    • point your browser to locahost:8003 or localhost:8004 as for linux
  • the CrabServer profile in your SshCLient should look like this

  • connection settings for SSH client: profile-1.gif

  • tunnelling settings for Ssh Client: profile-2.gif

Old Instructions using SOCKS and proxy not needed anymore and saved for my memory

For Mac

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng Firefox_Settings.png r1 manage 109.6 K 2011-06-16 - 18:05 StefanoBelforte  
PNGpng General.png r1 manage 35.1 K 2011-06-16 - 18:05 StefanoBelforte  
PNGpng Proxy_Details.png r2 r1 manage 44.9 K 2011-06-16 - 19:08 StefanoBelforte  
PNGpng URL_Patterns.png r1 manage 27.5 K 2011-06-16 - 18:05 StefanoBelforte  
PNGpng foxyproxy-options.png r1 manage 37.5 K 2011-06-16 - 18:06 StefanoBelforte  
GIFgif profile-1.gif r1 manage 16.6 K 2009-09-04 - 18:02 StefanoBelforte connection settings for SSH client
GIFgif profile-2.gif r1 manage 19.0 K 2009-09-04 - 18:03 StefanoBelforte tunnelling settings for Ssh Client
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Topic revision: r10 - 2014-01-14 - JamesLetts
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