RH134 Chapter 15 — Accessing Network-Attached Storage

Chapter Objective: Mount NFS and Samba/CIFS network shares manually and persistently, and configure autofs for on-demand mounting.

Key commands: showmount, mount -t nfs, autofs, mount -t cifs

Network Storage Protocols at a Glance

Protocol	Typical Use
NFS (Network File System)	The standard for sharing storage between Linux/Unix systems
SMB/CIFS (Samba)	Interoperating with Windows file shares, or Linux systems serving Windows clients

🔵 Why It Matters Unlike the local storage in Chapters 10–11, network-attached storage depends on the network being available — which introduces a whole category of failure modes (server down, permissions on the server side, network path issues) that local disks don't have.

Mounting NFS Shares Manually

# Discover what an NFS server is exporting, before mounting anything
showmount -e nfsserver.example.com

# Create a mount point
sudo mkdir -p /mnt/nfsdata

# Mount an NFS export
sudo mount -t nfs nfsserver.example.com:/exports/data /mnt/nfsdata

# Confirm it mounted
df -h /mnt/nfsdata

# Unmount when done
sudo umount /mnt/nfsdata

✅ Tip — showmount -e First Checking what a server actually exports before attempting to mount saves a round trip of guessing at the correct export path — and confirms the NFS server is reachable at all.

Persistent NFS Mounts with /etc/fstab

# /etc/fstab entry for an NFS mount
nfsserver.example.com:/exports/data  /mnt/nfsdata  nfs  defaults  0  0

# Test it without rebooting, same as any fstab entry (Chapter 10)
sudo mount -a

⚠️ Warning — A Down NFS Server Can Hang Boot An /etc/fstab entry for an NFS share that's unreachable at boot time can cause the system to hang or delay significantly while waiting for the mount. Consider adding options like _netdev (wait for network) and reasonable timeout behavior, or use autofs instead for shares that aren't always essential at boot.

On-Demand Mounting with autofs

autofs mounts a network share automatically the moment it's accessed, and unmounts it again after a period of inactivity — avoiding the boot-time dependency risk of a permanent fstab entry, and saving resources for shares that aren't constantly in use.

# Install autofs if not already present
sudo dnf install autofs

# /etc/auto.master — maps a mount point prefix to a map file
/mnt/auto  /etc/auto.mnt

# /etc/auto.mnt — the actual map, defining what mounts where
# key       options                    location
data        -fstype=nfs,rw             nfsserver.example.com:/exports/data

# Enable and start the service
sudo systemctl enable --now autofs

# Accessing this path triggers the mount automatically
ls /mnt/auto/data

🔵 Note With autofs, you never manually run mount — simply accessing the path (like cd'ing into it or listing it) is what triggers the mount to happen, and it disappears again after being idle.

Mounting Samba/CIFS Shares

# Install the CIFS mount utilities if needed
sudo dnf install cifs-utils

# Mount a Windows/Samba share, prompting for a password
sudo mount -t cifs //fileserver.example.com/shared /mnt/winshare -o username=student

# Store credentials in a protected file instead of typing them each time
sudo mount -t cifs //fileserver.example.com/shared /mnt/winshare -o credentials=/etc/samba/creds

# /etc/fstab entry using a credentials file
//fileserver.example.com/shared  /mnt/winshare  cifs  credentials=/etc/samba/creds  0  0

⚠️ Warning — Protect the Credentials File A credentials file contains a plaintext username and password. Restrict its permissions tightly (chmod 600, owned by root) — anyone who can read it can authenticate as that account against the share.

Troubleshooting Network Storage

# Confirm basic network reachability to the server
ping nfsserver.example.com

# Confirm the export is actually visible
showmount -e nfsserver.example.com

# Check what's currently mounted, and how
mount | grep nfs

# Check recent kernel/service messages related to the mount
journalctl -xe | grep -i nfs

Symptom	Likely Cause
Mount hangs indefinitely	Server unreachable, or firewall blocking the required ports
"Permission denied" after mounting	Server-side export permissions or client UID/GID mismatch
Mount succeeds but disappears later	autofs idle timeout (expected) vs. an unexpected disconnect (not expected)

✅ Tip — Separate "Can't Reach It" from "Reached It, Denied" A hanging mount and a "permission denied" mount point to very different problems — the first is almost always network/firewall, the second is almost always server-side export configuration or user/group mapping. Diagnose accordingly rather than guessing.

Key Terms for Chapter 15

NFS: Network File System; the standard protocol for sharing storage between Linux/Unix systems
export: A directory an NFS server makes available for clients to mount
showmount: Queries an NFS server to list what it currently exports
autofs: Service that mounts network shares on demand and unmounts them after idle time
SMB/CIFS: The protocol used by Windows and Samba file shares
credentials file: A protected file storing a username/password for mounting a CIFS share without typing them interactively

Review Questions

What command lets you check what an NFS server is exporting before attempting to mount anything?
Why can a permanent /etc/fstab entry for an NFS share be risky at boot time if the server is unreachable?
What problem does autofs solve compared to a static fstab entry for a network share?
Why should a CIFS credentials file have restricted permissions?
A network share mount hangs indefinitely with no error. What's the most likely category of problem?
A network share mounts successfully, but every file access returns "permission denied." What's the most likely category of problem this time?
Write a command that mounts a Samba share at //fileserver.example.com/shared onto /mnt/winshare using a credentials file at /etc/samba/creds.