Red Hat Bugzilla – Bug 1479251
NFS over UDP does not work
Last modified: 2017-09-19 00:02:03 EDT
Description of problem:
After upgrading from F24 to F26 a number of diskless clients (embedded systems) stopped working. They load the kernel image and DTB over NFS, and/or mount the rootfs over NFS. In both cases, NFS over UDP is used. For Linux mounting the rootfs thisis not really mandatory, but for the bootloader (U-Boot) fetching the kernel image it is, since U-Boot implements only UDP.
With F25 and F26, this stopped working. Apparently the Linux kernel in these releases does not support NFS over UDP any more.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Easy test: try mounting a Filesystem over NFS using UDP protocol:
mount -o udp server:/dir /dir
# mount -o udp sisyphus:/opt/tmp /mnt/tmp
mount.nfs: requested NFS version or transport protocol is not supported
Mount should succeed.
This restriction is blocking a pretty large number of devices from booting.
Falling back F24 on the file server is not really an option as it is no longer maintained.
I noticed the same behaviour when I upgraded from fc24 to fc26. NFS server hosted on fc26 does not seem to accept UDP connections. Not sure if this is a bug or this is how things are supposed to be.