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1 OpenAFS to NFSv4 Frequently Asked Questions

At Old Dominion University, the LIONS (Large Integrated Online Networked Services) “General Purpose” UNIX/Linux resources supported by ITS have used OpenAFS to store user home directories for the past several years.

Starting in May 2024, the Old Dominion University ITS department will begin the process of migrating user home directories from the existing OpenAFS servers to NFSv4 storage on the University’s NetApp file servers. This process is slated to be complete by the end of June 2024.

Near the end of the process, both the LIONS web and ftp servers will be migrated to use the new location of your home directory.

1.1 Here is what you need to know

• This migration affects your existing home directory that begins with either /afs/lions.odu.edu or /afs/pprd.odu.edu.
• To make things simpler, the new home directory path will begin with /nfs. In other words, if your existing home directory starts with /afs/lions.odu.edu/, your migrated home directory will start with /nfs/lions.odu.edu/.

1.2 Why the switch from OpenAFS to NFSv4?

• The OpenAFS servers are running RHEL 7, which Red Hat stated will be end of life on June 30, 2024, so they need to be replaced as soon as we can.

• NFS (or Network File System) is one of the standard internet protocols for file sharing and does not require a separate client like OpenAFS does. NFSv4 (i.e., Network File System version 4) is vastly different from its predecessors: it offers a stateful server, strong security, scalability/WAN features, and callbacks, among other things [1]. The latest version of NFS, version 4.2, includes many security features[2] such as

  • Security is based on usernames, not user ID’s. The result is that it is more difficult for an intruder to spoof credentials to gain access to data on an NFSv4 server.
  • You can also easily tell which clients are actively using NFSv4. It’s often impossible to know for sure with NFSv3 (Network File System version 3). You might know a certain client mounted a filesystem at some point in the past, but are they still using the files? Is the filesystem still mounted now? You can’t know for sure with NFSv3.
• We are going to use NFSv4 on ODU’s NetApp storage area network or SAN. A SAN is block-based storage, leveraging a high-speed architecture that connects servers to their logical disk units (LUNs). A LUN is a range of blocks provisioned from a pool of shared storage and presented to the server as a logical disk. The server partitions and formats those blocks - typically with a file system - so that it can store data on the LUN just as it would on local disk storage.

1.3 How to prepare for the migration

• If you have been using your LIONS account frequently or logging into lin-login.lions.odu.edu, you might want to look over your files and folders and clean up any old or duplicate data that you might have.

• Make note of any symbolic links[3] in your home directory. Either

  • make sure they are relative links or
  • be prepared to update them after the migration.

  For example, here is an existing link pointing to a file in a test user’s home directory.

       $ cd ~
       $ ls -la test1 test2
       -rw-rw-r-- 1 atestuser atestuser  0 Apr 25 10:16 test1
       lrwxrwxrwx 1 atestuser atestuser 10 Apr 25 10:17 test2 -> /afs/lions.odu.edu/home/a/atestuser/test1

  You can change it to a relative link like this:

       $ cd ~
       $ ln -sf test1 test2
       $ ls -la test1 test2
       -rw-rw-r-- 1 atestuser atestuser  0 Apr 25 10:16 test1
       lrwxrwxrwx 1 atestuser atestuser 10 Apr 25 10:17 test2 -> test1

  Or recreate the link after the migration:

       $ cd ~
       $ ln -sf test1 "${HOME}/test2"
       $ ls -la test1 test2
       -rw-rw-r-- 1 atestuser atestuser  0 Apr 25 10:16 test1
       lrwxrwxrwx 1 atestuser atestuser 10 Apr 25 10:17 test2 -> /nfs/lions.odu.edu/home/a/atestuser/test1

1.4 What will happen in May 2024

• This schedule is very fluid, so please be patient with us during the transition.
• We plan to start adding NFS support to the lin-login.lions.odu.edu followed shortly by www.lions.odu.edu and ftp.lions.odu.edu.

References

[1] M. Chen, D. Hildebrand, G. Kuenning, S. Shankaranarayana, B. Singh, and E. Zadok, “Newer Is Sometimes Better: An Evaluation of NFSv4.1.” [Online]. Available: https://www.fsl.cs.sunysb.edu/docs/nfs4perf/nfs4perf-sigm15.pdf.

[2] steiner, “NFSv3 and NFSv4: What’s the difference?” [Online]. Available: https://community.netapp.com/t5/Tech-ONTAP-Blogs/NFSv3-and-NFSv4-What-s-the-difference/ba-p/441316.

[3] “Symbolic Link.” [Online]. Available: https://en.wikipedia.org/wiki/Symbolic_link\#Overview.