NFS and autofs cheat sheet

The chapter on one page: what to remember, the commands to have at your fingertips, and flashcards for quick revision.

The chapter in eight sentences

NFS lets a client mount a directory that lives on a server; the server lists it in /etc/exports, runs nfs-server and opens the nfs firewall service.
An exports line is path host(options); apply changes with exportfs -ra and check with exportfs -v.
Mount with mount -t nfs serverb:/srv/shared /mnt/shared; NFSv4 needs only TCP port 2049.
The server decides access by numeric user ID, so the same UID must mean the same person on both machines.
root_squash (the default) turns the client's root into an unprivileged user; ro exports refuse all writes.
Permanent mount: an fstab line serverb:/srv/shared /mnt/shared nfs defaults,_netdev 0 0, tested with mount -a.
autofs mounts on first use and unmounts after a timeout: a master entry in /etc/auto.master.d/NAME.autofs points to a map file.
Wildcard map * -rw,sync serverb:/srv/homes/& serves many directories; a direct map uses /- and full paths; reload with systemctl reload autofs.

Command	Does
`/srv/shared 172.25.250.0/24(rw,sync)`	A line in `/etc/exports`
`exportfs -ra` · `exportfs -v`	Apply and list the exports
`systemctl enable --now nfs-server`	Start the server
`firewall-cmd --permanent --add-service=nfs` · `--reload`	Open the port
`ro` · `rw` · `root_squash` · `no_root_squash`	Common options

Command	Does
`mount -t nfs serverb:/srv/shared /mnt/shared`	Mount
`findmnt -t nfs4` · `nfsstat -m`	Show NFS mounts
`umount /mnt/shared`	Unmount
`ls -ln`	Show raw UIDs
fstab	`serverb:/srv/shared /mnt/shared nfs defaults,_netdev 0 0`

Item	Does
`dnf install autofs` · `systemctl enable --now autofs`	Install and start
`/etc/auto.master.d/NAME.autofs`	`/mnt/auto /etc/auto.NAME`
map line	`key -rw,sync serverb:/srv/dir`
wildcard	`* -rw,sync serverb:/srv/homes/&`
direct map	master `/- /etc/auto.direct`, key a full path
`systemctl reload autofs` · `automount -m`	Reload, show loaded maps

Server side in four steps?: mkdir share · /etc/exports line · systemctl enable --now nfs-server · exportfs -rav; firewall nfs service
An exports line?: /srv/shared 172.25.250.0/24(rw,sync) — path, host(options)
Show exports?: exportfs -v (server) · showmount -e SERVER (needs NFSv3 ports)
Client mount?: mount -t nfs server:/srv/shared /mnt/shared · df -hT · nfsstat -m
Permanent client mount?: server:/srv/shared /mnt/shared nfs defaults,_netdev 0 0
What crosses NFS?: Numeric UIDs and GIDs; use the same numbers on both sides.
root_squash?: Client root becomes nobody on the server (default). Fix permissions, not the squash.
No route to host / access denied / Permission denied?: Firewall / exports / UIDs and modes
Install and start autofs?: dnf install autofs · systemctl enable --now autofs · reload after edits
Indirect map?: /etc/auto.master.d/x.autofs: /mnt/auto /etc/auto.x --timeout=20 · /etc/auto.x: key -rw server:/dir
Wildcard home directories?: * -rw,sync server:/srv/homes/&
Direct map and checking?: /- /etc/auto.direct with full paths · automount -m · journalctl -u autofs