Note_Tech

All technological notes.

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Linux - Storage: NFS

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• Linux - Storage: NFS
  • NFS (Network File System)
    • Architecture
    • Package and Service
  • Server
  • Client
  • Lab: Create an NFS Server
  • Lab: Configure NFS Client
  • Package: AutoFS
    • Configuration File
    • AutoFS Maps
    • Lab: Direct Map
    • Lab: Indirect map
    • Lab: Auto mounting User Home

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NFS (Network File System)

• NFS (Network File System)

  • a distributed file system protocol that allows systems to share directories and files over a network as if they were locally mounted.
  • It was developed by Sun Microsystems and is widely used in Linux and Unix environments.

• Features

  • File Sharing:
    • Enables users to access and share files across a network.
  • Transparency:
    • Files appear to reside locally, even when they are on a remote server.
  • Platform Independence:
    • Allows different operating systems to share files.
  • Authentication and Security:
    • Supports features like Kerberos for secure authentication.
  • Versatility:
    • Used in small networks as well as large-scale enterprise environments.

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Architecture

• Server:
  • Hosts shared directories and manages access to them.
  • Runs the NFS server daemon to handle client requests.
• Client:
  • Mounts the shared directory from the NFS server.
  • Accesses files over the network as if they are on the local file system.

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Package and Service

• Package

sudo dnf install nfs-utils
rpm -qa | grep nfs-utils

• Services

sudo systemctl enable --now nfs-server rpcbind
sudo systemctl status nfs-server

# Test Exported Directories:
showmount -e server_ip

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Server

• Configuration Files: /etc/exports

  • contains a list of directories that can be exported to NFS clients.
  • The server automatically exports these directories each time it starts.

• Format

# share_dir client_ip (permissions)
/shared_directory 192.168.1.0/24(rw,sync,no_root_squash)
# share with everyone
/shared_directory *(rw,sync,no_root_squash)

• Permission

Permission	Desc
rw	Read-write access.
sync	Write changes to disk immediately.
no_root_squash	Allows root access from the client.

• Check Logs
  • /var/log/messages or /var/log/syslog

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• Common Commands

CMD	DESC
exportfs -v	List all exported directories
sudo exportfs -r	Apply the changes

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Client

• Configuration Files: /etc/fstab
  • a file on client that specifies persistent mounts for NFS shares.
  • Make Mount Persistent

server_ip:/shared_dir /mount_point nfs defaults 0 0

• Check Logs
  • /var/log/messages or /var/log/syslog

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• Common Commands

CMD	DESC
sudo mount -t nfs server_ip:/shared_dir /mount_point	Mount the NFS share
sudo umount /mount_point	Unmount a share

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Lab: Create an NFS Server

• install packages

yum install nfs-utils -y
rpm -qa | grep nfs
# nfs-utils-2.3.3-59.el8.x86_64
# libnfsidmap-2.3.3-59.el8.x86_64
# sssd-nfs-idmap-2.9.4-5.el8_10.1.x86_64

• Enable service

systemctl enable rpcbind
systemctl enable nfs-server
systemctl start rpcbind nfs-server rpc-statd nfs-idmapd

• Create share resource

# create dedicated dir for sharing
mkdir /shared_data
chmod 755 /shared_data
# create resource
touch /shared_data/resource
echo "this is resource on server" > /shared_data/resource

• Edit exports file

# backup exports
cp /etc/exports /etc/exports.bak
vi /etc/exports
# /shared_data 192.168.1.0/24(rw,sync,no_root_squash)

• Export fs

exportfs -rv
# exporting 192.168.1.0/24:/shared_data

• Disable firewall

firewall-cmd --permanent --add-service nfs
firewall-cmd --reload
firewall-cmd --list-all

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Lab: Configure NFS Client

• Install packages

dnf install nfs-utils rpcbind -y
rpm -qa | grep nfs
# sssd-nfs-idmap-2.9.4-5.el8_10.1.x86_64
# nfs-utils-2.3.3-59.el8.x86_64
# libnfsidmap-2.3.3-59.el8.x86_64

• Enable service

systemctl enable rpcbind
systemctl start rpcbind
systemctl status rpcbind

• Stop firewall or iptables

ps -ef | egrep "firewall|iptable"
# stop firewall
systemctl stop firewalld
systemctl status firewalld

• Show available mount from the NFS server

showmount -e 192.168.1.130
# Export list for 192.168.1.130:
# /shared_data 192.168.1.0/24

• mount

# create mount point
mkdir /mnt/app
mount 192.168.1.130:/shared_data /mnt/app

# verify
df -h
# Filesystem                      Size  Used Avail Use% Mounted on
# devtmpfs                        1.8G     0  1.8G   0% /dev
# tmpfs                           1.8G     0  1.8G   0% /dev/shm
# tmpfs                           1.8G  9.7M  1.8G   1% /run
# tmpfs                           1.8G     0  1.8G   0% /sys/fs/cgroup
# /dev/mapper/rhel_rhelhost-root   26G  7.9G   19G  31% /
# /dev/nvme0n1p1                 1014M  424M  591M  42% /boot
# tmpfs                           364M   24K  364M   1% /run/user/1001
# 192.168.1.130:/shared_data       26G  7.5G   19G  29% /mnt/app

• Manipulate resource from client

# access to resource
ll /mnt/app
# total 4
# -rw-r--r--. 1 root root 27 Dec 21 00:57 resource

cat /mnt/app/resource
# this is resource on server

# create dir and file
mkdir /mnt/app/client
echo "this is data from client" > /mnt/app/client/test

# verify on server
cat /shared_data/client/test
# this is data from client

• unmount
  • kill the seesion working on the nfs before unmounting

umount /mnt/app

• Persist NFS share on client

echo "192.168.1.130:/shared_data /mnt/app nfs _netdev 0 0"

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Package: AutoFS

• Auto File System (AutoFS)

  • a service that mounts and unmounts a share on the clients during runtime as well as system reboots.
  • a client-side service
• With a proper entry placed in AutoFS configuration files, the AutoFS service automatically mounts a share upon detecting an activity in its mount point with a command such as ls or cd.

• To avoid inconsistencies, mounts managed with AutoFS should not be mounted or unmounted manually or via the /etc/fstab file.

• maps
  • NFS shares be defined in text configuration files
  • CF location: /etc/auto.master.d

• With AutoFS, a share is unmounted automatically if it is not accessed for five minutes by default.

• automount
  • the daemon of AutoFS service
  • invoked at system boot
  • It reads the AutoFS master map and creates initial mount point entries, but it does not mount any shares yet.
  • When the service detects a user activity under a mount point during runtime, it mounts the requested file system at that time.
  • If a share remains idle for a certain time period, automount unmounts it by itself.

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Configuration File

• /etc/autofs.conf

• Sample:

[ autofs ]
timeout = 300
browse_mode = no
mount_nfs_default_protocol = 4
[amd]
dismount_interval = 300

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AutoFS Maps

• 3 common AutoFS map types:
  • master
    • location: /etc/auto.master
  • direct
    • used to mount shares automatically on any number of unrelated mount points.
    • always visible to users
    • Local and direct mounted shares can coexist under one parent directory.
  • indirect
    • when need to mount all of the shares under one common parent directory.
    • visible only after they have been accessed.
    • Local and indirect mounted shares cannot coexist under the same parent directory.

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Lab: Direct Map

dnf install -y autofs

showmount -e 192.168.128.50
# Export list for 192.168.128.50:
# /home/guests/netuserX 192.168.128.0/24

# create mount point
mkdir /autodir

# add entry in master file
vi /etc/auto.master
/-  /etc/auto.master.d/auto.dir

# create file and map mount point
vi etc/auto.master.d/auto.dir
/autodir 192.168.128.50:/home/guests/netuserX

# confirm autofs running
systemctl status autofs.service -l --no-pager

# confirm
ll /autodir
# total 4
# -rw-r--r--. 1 xanadu xanadu 22 Jan 31 14:21 testfile

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Lab: Indirect map

# create mount point
mkdir /indirect

# edit misc file
vi /etc/auto.misc
autoindir 192.168.128.50:/home/guests/netuserX

# confirm
ll /misc/autoindir/
# total 4
# -rw-r--r--. 1 xanadu xanadu 22 Jan 31 14:21 testfile

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Lab: Auto mounting User Home

• Server:
  • Create user netuserX with UID 3000
  • Add home directory /home/netuserX to the list of NFS shares.

useradd -u 3000 netuserX
echo password | passwd --stdin netuserX

# add entry
echo "/home 192.168.128.0/24(rw)" >> /etc/exports

# export all share
exportfs -avr
# exporting 192.168.128.50:/home
# exporting 192.168.128.0/24:/home/guests/netuserX

• Client:
  • Create user netuserX with UID 3000 and no home dir.
  • Create mount poit /nfshome
  • Create indirect map to the remote user home.

# create user
# -M: no home dir
# -b: specify base dir
useradd netuserX -u 3000 -Mb /nfshome
echo password | passwd --stdin netuserX

# create mount point
mkdir /nfshome

# add entry to master
echo "/nfshome  /etc/auto.master.d/auto.home" >> /etc/auto.master

# create cf
echo "* -rw 192.168.128.50:/home/netuserX" > /etc/auto.master.d/auto.home

# confirm
su - netuserX
pwd
# /nfshome/netuserX