This is a quick tutorial for EOS.

EOS is an open-source storage software solution to manage multi PB storage for the CERN Large Hadron Collidor LHC. Core of the implementation is the XRootD framework providing a feature-rich remote access protocol.

• Setup your environment: You need to define your default EOS instance (management server),
  e.g.
  • export EOS_MGM_URL=root://eos<experiment>.cern.ch
  • export EOS_MGM_URL=root://eosuser.cern.ch

• EOS Kerberos Ticket
  To access the storage, you need a CERN Kerberos ticket. Create such a ticket with the following command:
  kinit <cern_username>@CERN.CH

• EOS commands are often very similar to Unix (for example ls –> eos ls).
  e.g.
  • eos mkdir /eos/lhcb/user/b/bla/blabla
  • eos ls /eos/lhcb/user/b/bla/blabla

• EOS commands including management server:
  You don't need to define a default EOS instance, you can add it to the eos command:
  eos root://eoslhcb.cern.ch ls -l /eos/lhcb/user/b/bla/blabla

• EOS command list:
  A list of all EOS commands is given with eos help.

On our cluster some of the EOS instances are mounted with fuse, so they look like normal file systems to you and you can use standard linux commands. The mounted file systems are:

• eoscms –> /eos/cms/
• eoslhcb –> /eos/lhcb/
• eosuser –> /eos/user/

To access these file systems, you need to have a CERN Kerberos ticket as for the EOS commands, but in addition you need to pass the ticket to the fuse system with the command eosfusebind, similar to the aklog command for AFS. You need therefore to execute the following commands:
kinit <cern_username>@CERN.CH ; eosfusebind

EOS commands and Linux commands in the EOS file system are not very resource efficient. If you need to transfer large amount of data, use the xrdcp command:

• xrdcp root://eoslhcb.cern.ch//eos/lhcb/user/b/bla/eos_tutorial/eos.txt eos.txt
• xrdcp eos.txt root://eoslhcb.cern.ch//eos/lhcb/user/b/bla/eos_tutorial/eos.txteos.txt