RHEL 8 New Features for Experienced Linux Administrators

Install all necessary packages to export NFS shares on servera.

1. Log in to servera as the root user.

   [student@workstation ~]$ ssh root@servera

2. Install the nfs-utils package on servera, if not already installed.

   [root@servera ~]# yum install nfs-utils
   ...output omitted...
   Is this ok [y/N]: y
   ...output omitted...

3. Enable the nfs-server service on servera to start at boot time.

   [root@servera ~]# systemctl enable --now nfs-server
   Created symlink /etc/systemd/system/multi-user.target.wants/nfs-server.service → /usr/lib/systemd/system/nfs-server.service.

Using the nfsconf command to configure /etc/nfs.conf, enable NFS Server to work in just version 4.X, and also ensure that TCP mode is enabled and UDP mode is disabled.

1. Review the available tags and sections in the /etc/nfs.conf file.

   [root@servera ~]# cat /etc/nfs.conf
   #
   # This is a general configuration for the
   # NFS daemons and tools
   ...output omitted...
   [nfsd]
   # debug=0
   # threads=8
   # host=
   # port=0
   # grace-time=90
   # lease-time=90
   # tcp=y
   # vers2=n
   # vers3=y
   # vers4=y
   # vers4.0=y
   # vers4.1=y
   # vers4.2=y
   # rdma=n
   #
   ...output omitted...

2. Disable the tags udp, vers2, vers3, configure them with nfsconf tool.

   [root@servera ~]# nfsconf --set nfsd udp n
   [root@servera ~]# nfsconf --set nfsd vers2 n
   [root@servera ~]# nfsconf --set nfsd vers3 n

3. Enable the tags vers4, vers4.0, vers4.1, vers4.2 , configure them with nfsconf tool.

   [root@servera ~]# nfsconf --set nfsd tcp y
   [root@servera ~]# nfsconf --set nfsd vers4 y
   [root@servera ~]# nfsconf --set nfsd vers4.0 y
   [root@servera ~]# nfsconf --set nfsd vers4.1 y
   [root@servera ~]# nfsconf --set nfsd vers4.2 y

4. Disable listening for the RPCBIND, MOUNT, and NSM protocol calls, which are not necessary in the NFSv4-only case. Disable related services:

   [root@servera ~]# systemctl mask --now rpc-statd.service \
   > rpcbind.service rpcbind.socket
   Created symlink /etc/systemd/system/rpc-statd.service → /dev/null.
   Created symlink /etc/systemd/system/rpcbind.service → /dev/null.
   Created symlink /etc/systemd/system/rpcbind.socket → /dev/null.

5. Restart the nfs-server service to apply the changes.

   [root@servera ~]# systemctl restart nfs-server

Configure firewalld on servera to allow incoming connections for the NFSv4 Server.

1. Inspect which ports are listening, on servera as root with the ss command.

   [root@servera ~]$ ss --listening --tcp --udp
   Netid  State   Recv-Q  Send-Q  Local Address:Port  Peer Address:Port
   udp    UNCONN  0       0           127.0.0.1:323        0.0.0.0:*
   udp    UNCONN  0       0               [::1]:323           [::]:*
   tcp    LISTEN  0       128           0.0.0.0:ssh        0.0.0.0:*
   tcp    LISTEN  0       64            0.0.0.0:nfs        0.0.0.0:*
   tcp    LISTEN  0       128              [::]:ssh           [::]:*
   tcp    LISTEN  0       64               [::]:nfs           [::]:*
   tcp    LISTEN  0       128                 *:websm            *:*

2. Configure firewalld on servera to allow NFSv4 service.

   [root@servera ~]# firewall-cmd --add-service=nfs
   success

3. Make the firewalld changes persistent with firewall-cmd.

   [root@servera ~]# firewall-cmd --runtime-to-permanent
   success

4. List the services enabled on firewalld.

   [root@servera ~]# firewall-cmd --list-services
   cockpit dhcpv6-client nfs ssh

Configure servera to export content with NFSv4 Server.

1. Create a folder on servera to export content.

   [root@servera ~]# mkdir /exports

2. Change the /exports folder ownership to the user nobody and group nobody.

   [root@servera ~]# chown nobody:nobody /exports

3. Configure and restore SELinux contexts on the /exports folder.

   [root@servera ~]# semanage fcontext -a -t public_content_rw_t "/exports(/.*)?"
   [root@servera ~]# restorecon -vvFR /exports/

4. Export the /exports folder by creating a new configuration file in /etc/exports.d/

   [root@servera ~]# echo "/exports *(rw,security_label)" > \
   > /etc/exports.d/example.exports

5. Reload the NFSv4 exports:

   [root@servera ~]# exportfs -r

6. Log out from servera.

   [root@servera ~]# exit
   Connection to servera closed.

Configure serverb as client system of servera NFSv4 exports, and use autofs.

1. Log in to serverb as the root user.

   [student@workstation ~]$ ssh root@serverb

2. Install the autofs package on serverb.

   [root@serverb ~]# yum install autofs
   ...output omitted...
   Is this ok [y/N]: y
   ...output omitted...

3. Enable the autofs service on serverb to start at boot time.

   [root@serverb ~]# systemctl enable --now autofs
   Created symlink /etc/systemd/system/multi-user.target.wants/autofs.service → /usr/lib/systemd/system/autofs.service.

4. Create a mount point folder on serverb.

   [root@serverb ~]# mkdir -p /mnt/exports

5. Configure a new master map file, name it as /etc/auto.master.d/example.autofs on serverb

   [root@serverb ~]# echo "/mnt/exports  /etc/auto.exports" > \
   > /etc/auto.master.d/example.autofs

6. Configure /etc/auto.exports with a map-file on serverb

   [root@serverb ~]# cat << EOF > /etc/auto.exports
   > example  -fstype=nfs4  servera.lab.example.com:/exports/example
   > EOF

7. Restart the autofs service to apply the changes.

   [root@serverb ~]# systemctl restart autofs

Test the autofs and NFSv4 Server, create some small text content file on servera and review it on serverb. When done, log out from serverb.

1. Switch to servera to create a subdirectory /exports/example and then create a text file inside the folder.

   [root@servera ~]# mkdir -p /exports/example
   [root@servera ~]# echo "Test from $(hostname)" > /exports/example/TEST

2. On serverb, use autofs to explore the on-demand mount point exported on servera. Verify the SELinux context.

   [root@serverb ~]# cd /mnt/exports/example
   [root@serverb example]# ls -lZ
   tal 4
   -rw-r--r--. 1 root root system_u:object_r:public_content_rw_t:s0 34 May 19 17:24 TEST
   [root@serverb example]# cat TEST
   Test from servera.lab.example.com

3. Explore the mount options for the NFSv4 auto mounted share.

   [root@serverb example]# mount | grep nfs4
   servera.lab.example.com:/exports/example on /mnt/exports/example type nfs4
   (rw,relatime,seclabel,vers=4.2,rsize=524288,wsize=524288,namlen=255,hard,
   proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=172.25.250.11,local_lock=none,
   addr=172.25.250.10)

4. Log out from serverb.

   [root@serverb example]# exit
   [student@workstation ~]$