NFS mount timeout - linux-kernel

Question

Like this, my server-side configure is /lenge/gnu/aarch64_sysroot_nfs 192.168.137.8(rw,sync,no_subtree_check) in /etc/exports.
[ 4.995341] Root-NFS: nfsroot=/lenge/gnu/aarch64_sysroot_nfs
[ 4.999167] NFS: nfs mount opts='vers=2,udp,rsize=4096,wsize=4096,nolock,addr=192.168.137.188'
[ 5.001094] NFS: parsing nfs mount option 'vers=2'
[ 5.002329] NFS: parsing nfs mount option 'udp'
[ 5.002843] NFS: parsing nfs mount option 'rsize=4096'
[ 5.004294] NFS: parsing nfs mount option 'wsize=4096'
[ 5.004996] NFS: parsing nfs mount option 'nolock'
[ 5.005533] NFS: parsing nfs mount option 'addr=192.168.137.188'
[ 5.008949] NFS: MNTPATH: '/lenge/gnu/aarch64_sysroot_nfs'
[ 5.010838] NFS: sending MNT request for 192.168.137.188:/lenge/gnu/aarch64_sysroot_nfs
[ 5.138789] NFS: MNT request succeeded
[ 5.139382] NFS: Faking up auth_flavs list
[ 5.144674] NFS: attempting to use auth flavor 1
[ 10.357008] NFS: nfs mount opts='vers=2,udp,rsize=4096,wsize=4096,nolock,addr=192.168.137.188'
[ 10.357996] NFS: parsing nfs mount option 'vers=2'
[ 10.358620] NFS: parsing nfs mount option 'udp'
[ 10.359131] NFS: parsing nfs mount option 'rsize=4096'
[ 10.359734] NFS: parsing nfs mount option 'wsize=4096'
[ 10.360856] NFS: parsing nfs mount option 'nolock'
[ 10.361537] NFS: parsing nfs mount option 'addr=192.168.137.188'
[ 10.362440] NFS: MNTPATH: '/lenge/gnu/aarch64_sysroot_nfs'
[ 10.363178] NFS: sending MNT request for 192.168.137.188:/lenge/gnu/aarch64_sysroot_nfs
[ 10.377199] NFS: MNT request succeeded
[ 10.377666] NFS: Faking up auth_flavs list
[ 10.378161] NFS: attempting to use auth flavor 1
So then, what is the problem？

Answer 1

I had this problem as well. My /etc/exports looked like yours, but my problem was with my uEnv.txt, specifically how I was telling the kernel to mount the rootfs via NFS. See my image that summarizes the problem and solution.
In section 2 of the nfsroot.txt
kernel doc for the BeagleBoneBlack it states that the NFS device and where to locate it need to be passed to the kernel in the following manner:
root=/dev/nfs
This is necessary to enable the pseudo-NFS-device. Note that it's not a
real device but just a synonym to tell the kernel to use NFS instead of
a real device.
nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
If the `nfsroot' parameter is NOT given on the command line,
the default "/tftpboot/%s" will be used.
Specifies the IP address of the NFS server.
The default address is determined by the `ip' parameter
(see below). This parameter allows the use of different
servers for IP autoconfiguration and NFS.
Name of the directory on the server to mount as root.
If there is a "%s" token in the string, it will be
replaced by the ASCII-representation of the client's
IP address.
Standard NFS options. All options are separated by commas.
The following defaults are used:
port = as given by server portmap daemon
rsize = 4096
wsize = 4096
timeo = 7
retrans = 3
acregmin = 3
acregmax = 60
acdirmin = 30
acdirmax = 60
flags = hard, nointr, noposix, cto, ac
I did add nfsvers=3 to my nfs-options as per #Sam Protsenko's suggestion, but I'm not sure if this alone or this combined with mentioned changes is what cause the kernel to mount the rootfs.
In my original uEnv.txt 'rootwait' & 'rootdelay=5' appear to be deprecated. NFS reported that those parameters were unrecognized when attempting to parse, so I removed them in my updated uEnv.txt.
If none of this doesn't help you, you can gather more information using the following:
found here

Answer 2

I to faced a similar kind of problem. Once the correct nfs options are given the issue got solved. The nfs options are documented in: nfs options. This kernel documentation is not updated. So to view the current set of options supported you can pass 'nfsrootdebug' in the kernel command line parameters. This will list the current list of nfs options that are currently supported. If this options is passed the kernel boot log will look like this:
You choose the appropriate option from the list.