The AFS (Andrew File System) is a so-called network file system that allows the storage of data on a central storage system at DESY. In addition, it allows access to data made available via the AFS to other institutes which also use the AFS.

The AFS is composed of so-called AFS cells. These are administrative spaces that are provided by central computers (servers) at the respective institute. The directories of DESY's own AFS cell are accessible from Linux systems, for example, via the path /afs/desy.de. On Windows computers using the Windows Explorer via the path \\afs\desy.de.

Since many other institutes and universities also use the AFS, you can also access data from other institutes if you have the necessary permissions. You can access this data by specifying the path to the corresponding AFS cell. For example /afs/cern.ch or \\afs\cern.ch.

To use the AFS storage system, an application is required, which enables people to connect to the AFS using their DESY account.

Access from Windows

To access AFS from Windows, you need the so-called Network Identity Manager, which you can install using the Windows software store DSM (Package name: "OpenAFS + NetIDMgr"). A short instruction on how to install it can be found on the following web site:

https://it.desy.de/services/soft/open_afs_with_the_network_identity_manager/

After you have installed it, restart your computer. In the future, you will be prompted by the Network Identity Manager to enter your password each time you log on to your Windows computer, this way the connection to the AFS can be established in the background.

Afterwards, the directories P: and Q: should be available to you in Windows Explorer.

• P is your personal AFS directory:
  \\afs\desy.de\user\[first letter of the accountname]\[accountname]
  
  Example for account theotest: \\afs\desy.de\user\t\theotest
   
• Q is the AFS group directory of your group:
  \\afs\desy.de\group\[Group abbreviation]
   

Please note that the validity of the logon ( indicated by a so-called AFS token) expires in any case after 24 hours if it is not renewed. Under Windows, it is possible to renew the so-called AFS token via the Network Identity Manager. For more information about the renewal of the AFS token and the general usage of the Network Identity Manager, please visit the following website:

https://it.desy.de/dienste/soft/open_afs_mit_network_identity_manager/

Access from Linux

On DESY standard computers, the AFS is available without the installation of further applications. On DESY Linux systems, logging on to the AFS is usually done automatically when logging on to the operating system. After logging in to the operating system, you can access your AFS directories using the following paths:

• Personal AFS directory:
  /afs/desy.de/user/[first letter of the accountname]/[accountname]
  
  Example for account theotest: /afs/desy.de/user/t/theotest
   
• Group directory:
  /afs/desy.de/group/[Group abbreviation]
   

Please note that the validity of the logon ( indicated by a so-called AFS token) expires in any case after 24 hours if it is not renewed. You can check whether you have a valid AFS token with the following command:

• tokens
   

If you want to renew your AFS token or do not have one (e.g. because it has expired in the meantime) and therefore need to create a new one, use the following command:

• aklog
   

A list of other useful commands can be found at the end of this web page.

Storage Space Management (Quota)

Each AFS personal directory has a default quota of 16 GB. If you need more space, please contact the administrators responsible for your group. You can find a list of contacts on the following website:

https://it.desy.de/services/uco/windows_group_admins

If you need a significantly larger amount of storage space in AFS, it makes sense to set up a personal AFS xxl directory. However, please consider that due to the amount of data, these types of directories are not backed up as frequently as your personal AFS directory. In some cases, you may also consider using other data storage systems instead of AFS, which are offered by DESY-IT. Information on possible options can be found on the following web page:

https://it.desy.de/services/uco/documentation/data_storage/

If you need advice, please contact your group administrator (see above) or the UCO (Tel: 5005, E-Mail. uco@desy.de).

AFS Access Rights (ACLs)

AFS uses Access Control Lists (ACLs) to control the permissions on the directories stored. The permissions apply exclusively on a directory basis and can therefore not be set for individual files.

Please note that existing subdirectories do not automatically receive the permissions set on the parent directory. After permissions are assigned, however, newly created subdirectories inherit the permissions from the parent directory.

Although the access permissions of the Linux or Windows file system are still displayed, the ACLs override them. For more information about how to use Access Control Lists in AFS, see the following web page if needed:

https://it.desy.de/services/uco/documentation/access_control_lists_in_the_afs_acls/

Backup

Each night, the state of each AFS account's personal directory is recorded in the special .OldFiles directory of that AFS personal directory. For theotest this would be e.g. /afs/desy.de/user/t/theotest/.OldFiles. Should you accidentally or intentionally delete data during the day and yet need it again, you will find this data in your .OldFiles directory. In addition, a central backup mechanism (via TSM) creates incremental backup copies, means those of modified files.

Overview of some helpful Commands

tokens

aklog

unlog

fs lq

Potential Problems

An overview of potential problems and their remedies related to the use of the AFS can be found on the following web page:

https://it.desy.de/services/uco/documentation/afs/afs_troubleshooting/

UCO Hamburg

Phone:	+49 (0)40 8998 5005
E-Mail:	UCO Hamburg
Location:	2b / 131d
Link:	https://it.desy.de/services/uco