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Submitting Jobs to HTCondor from a local Machine

The recommended way of using HTCondor is to submit jobs by logging to lxplus.cern.ch.

It is also possible to configure your own computer to manage HTCondor jobs, as described in this guide.

These notes refer to Ubuntu 16.04 LTS, 18.04 LTS and 20.04 LTS and includes possible caveats. If you have a different Linux distribution, steps might be the same, but syntax may change. Sudo rights are needed.

As pre-requisite, you will need to install a kerberos client on your desktop; afterwards, you can proceed with the installation of HTCondor

Install kerberos

install user and developer packages and add lxplus credential components (when asked, default realm is CERN.CH):

sudo apt install krb5-user libkrb5-dev libauthen-krb5-perl

scp $USERNAME@lxplus.cern.ch:/usr/bin/batch_krb5_credential .
chmod +x batch_krb5_credential 
sudo mv batch_krb5_credential /usr/bin/

scp $USERNAME@lxplus.cern.ch:/etc/ngauth_batch_crypt_pub.pem .
sudo mv ngauth_batch_crypt_pub.pem /etc/

scp $USERNAME@lxplus.cern.ch:/etc/krb5.conf.no_rdns .
sudo mv krb5.conf.no_rdns /etc/krb5.conf.no_rdns

scp $USERNAME@lxplus.cern.ch:/etc/sysconfig/ngbauth-submit .
sudo mkdir /etc/sysconfig/
sudo mv ngbauth-submit /etc/sysconfig/

Confirm installation

Before this step make sure you have valid credentials already (i.e. run kinit). Then check that the kerberos components are properly installed and set-up (the script will tell you the missing perl packages):

/usr/bin/batch_krb5_credential

There should be an output like:

-----BEGIN NGAUTH COMPOSITE-----
# LOTS OF LINES OF YOUR KEY

-----END NGAUTH COMPOSITE-----

and nothing else (i.e. no missing files or errors).

Debugging the kerberos installation

if the last step does not deliver the desired output, /usr/bin/batch_krb5_credential might have to be modified. Some things can be tried:

  1. change the line

    my $principalName = "ngauth/SOMESERVER";
    

    into

    my $principalName = "ngauth/ngauth.cern.ch"; 
    
  2. install missing perl components:

    perl -MCPAN -e 'install Authen::Krb5'
    
  3. on Ubuntu 20.04 neither of these steps helped, as the Authen:Krb5 package was not available. Try getting a new version of batch_krb5_credential directly from lxplus8:

    scp $USERNAME@lxplus8.cern.ch:/usr/bin/batch_krb5_credential .
    chmod +x batch_krb5_credential 
    sudo mv batch_krb5_credential /usr/bin/
    
  4. or try manual fix of Authen:Krb5 issue by replacing the lines:

    my $newCreds = Authen::Krb5::cc_resolve("FILE:".$tgt_fn);
    $newCreds->initialize($credCache->get_principal());
    Authen::Krb5::cc_copy_creds($credCache, $newCreds);
    

    with

    copy($tgt, $tgt_fn);
    

Install HTCondor

On Ubuntu 18.04+ it is usually enough to install condor from the packaged version

sudo apt update
sudo apt install htcondor
sudo apt-get update
sudo apt-get install condor

If you need a more recent version, or in case of Ubuntu 16.04, use the resources on the web-page of HTCondor.

Debugging the HTCondor installation

It may happen that at sudo apt-get update, you get the error message:

N: Skipping acquire of configured file 'contrib/binary-i386/Packages' as repository 'http://research.cs.wisc.edu/htcondor/ubuntu/stable trusty InRelease' doesn't support architecture 'i386'

In case your system is actually 64bit, a common solution is to limit the research of the package distro to just 64 bit by introducing the [arch=amd64] in the list of sources (in /etc/apt/sources.list), e.g.

deb [arch=amd64] http://research.cs.wisc.edu/htcondor/ubuntu/stable/ trusty contrib

Configure HTCondor

  1. create the config file /etc/condor/config.d/10-local.config.

    Please set as scheduler (SCHEDD_HOST) the default one you get on lxplus, e.g. in your condor_q output. You can also find it out by running (on lxplus):

    condor_config_val SCHEDD_HOST
    

    An example content is provided here:

    CONDOR_HOST = tweetybird03.cern.ch, tweetybird04.cern.ch
    COLLECTOR_HOST = tweetybird03.cern.ch, tweetybird04.cern.ch
    SCHEDD_HOST = bigbirdXX.cern.ch
    SCHEDD_NAME = $(SCHEDD_HOST)
    SEC_CLIENT_AUTHENTICATION_METHODS = KERBEROS
    SEC_CREDENTIAL_PRODUCER = /usr/bin/batch_krb5_credential
    CREDD_HOST = $(SCHEDD_HOST)
    FILESYSTEM_DOMAIN = cern.ch
    UID_DOMAIN = cern.ch
    
  2. restart HTCondor:

    /etc/init.d/condor restart
    

Debugging the HTCondor configuration

  1. Useful: The full configuration can be checked by

    condor_config_val -dump
    
  2. If you have connection problems when running condor_q or condor_status, you might want to check your NETWORK_INTERFACE.

    condor_config_val NETWORK_INTERFACE
    

    In some cases it might be set to 127.0.0.1 or similar. Yet it should be set to *. If this is not the case, simply add the appropriate line at the end of your configuration file (from above):

    NETWORK_INTERFACE = *
    

    Don't forget to restart HTCondor.

  3. Pay attention to the couple COLLECTOR_HOST and SCHEDD_HOST, as, depending on the collector, you may be able to reach only a sub-set of the scheduler. To get the whole lists, please login to lxplus.cern.ch and type:

    condor_status -sched 
    
    condor_status -collector