NFS (Network File System) ==========================   Basics ------ Network File System (NFS) is a distributed file system protocal originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network in a manner similar to how local storage is accessed.     A filesystem which supports the mapping between filehandle fragments and dentries will be termed "exportable". A filesystem must be "exportable" to be accessed from a remote computer.   /etc/exports: the access control list for filesystems which may be exported to NFS clients.  See exports(5).   How to make an nfs mount? server: modify /etc/exports to export some directories client: mount   <server_ip>/<exported_dir>   <local_dir>   Q & A ----- 1. nfsd on /proc/fs/nfsd type nfsd (rw) nfsd file system?   2. "Permission denied" problem on nfs client. 'no_root_squash' is not specified in the corresponding config item in /etc/exports.   3. What does 'no_root_squash' mean? 'no_root_squash' is a setting that allows nfs clients to connect as root.   Terminology ----------- distributed file system Open Network Computing Remote Procedure Call (ONC RPC) filehandle fragment exportable filesystems   NFS in yocto ------------ 1) Problem starting 8 nfsd kernel threads: rpc.nfsd: Unable to access /proc/fs/nfsd errno 2 (No such file or directory). Please try, as root, 'mount -t nfsd nfsd /proc/fs/nfsd' and then restart rpc.nfsd to correct the problem done 2) Status root@qemux86:/etc/rc5.d# ls -l | grep nfs lrwxrwxrwx    1 root     root            19 Dec 19 06:03 S20nfsserver -> ../init.d/nfsserver It seems that our yocto-based image could only be used as an nfs client. /proc/fs/nfsd is empty. Then why is nfsserver in /etc/init.d/ directory?   And we can see /etc/exports states that "/ *(rw,no_root_squash,async,no_subtree_check)". Is there anything wrong with the nfs server in our system?     Examples -------- 1) Examine /etc/exports on our servers.    Try it out on our servers.     References ---------- Linux Kernel Documents (<kernel src>/Documentation/filesystems/nfs/)   man exports   https://www.digitalocean.com/community/articles/how-to-set-up-an-nfs-mount-on-ubuntu-12-04 (How to set up an nfs mount on Ubuntu 12.04)