Exercise: Serve home directories on demand

Serve home directories on demand

• Create a wildcard map with * and &.
• Create a direct map with the /- master entry.
• Use automount -m and journalctl -u autofs to inspect maps.

Start the exercise

On workstation, start the exercise. It installs nfs-utils and autofs, exports /srv/shared from serverb to the lab network (NFS server running, firewall open), and starts autofs on servera.

[student@workstation ~]$ lab start sa-nfs-maps

Later tasks assume that you are logged in to the server they name: ssh student@servera from workstation, then sudo -i for a root shell.

The homes on the server

On serverb as root, create /srv/homes/alice and /srv/homes/student with a file readme in each, owned by the matching user (UID 2001 for alice; create the user if needed). Export /srv/homes to your lab network read-write and publish.

[student@workstation ~]$ ssh student@serverb
[student@serverb ~]$ sudo -i
[root@serverb ~]# id alice > /dev/null 2>&1 || useradd -u 2001 alice
[root@serverb ~]# mkdir -p /srv/homes/alice /srv/homes/student
[root@serverb ~]# echo "alice home" > /srv/homes/alice/readme; echo "student home" > /srv/homes/student/readme
[root@serverb ~]# chown -R alice:alice /srv/homes/alice; chown -R student:student /srv/homes/student
[root@serverb ~]# echo '/srv/homes  172.25.250.0/24(rw,sync)' >> /etc/exports
[root@serverb ~]# exportfs -ra; exportfs -v | cut -c1-60
/srv/shared   	172.25.250.0/24(sync,wdelay,hide,no_subtree_check,
/srv/homes    	172.25.250.0/24(sync,wdelay,hide,no_subtree_check,

The wildcard map on the client

On servera as root (autofs installed and running from the previous exercise; install it if not), create the master entry for /remote/homes and the wildcard map. Reload autofs and list the directory. Why is it empty?

[student@servera ~]$ sudo -i
[root@servera ~]# systemctl is-active autofs
active
[root@servera ~]# echo '/remote/homes  /etc/auto.homes' > /etc/auto.master.d/homes.autofs
[root@servera ~]# echo '*  -rw,sync  serverb:/srv/homes/&' > /etc/auto.homes
[root@servera ~]# systemctl reload autofs
[root@servera ~]# ls /remote/homes
[root@servera ~]#

Nothing is mounted until a key is used, so autofs has nothing to list yet.

Use two homes

Read alice's readme, then list the parent directory and the mounts. Do the same for student.

[root@servera ~]# cat /remote/homes/alice/readme
alice home
[root@servera ~]# ls /remote/homes
alice
[root@servera ~]# cat /remote/homes/student/readme
student home
[root@servera ~]# ls /remote/homes
alice  student
[root@servera ~]# mount | grep remote | cut -c1-75
/etc/auto.homes on /remote/homes type autofs (rw,relatime,fd=15,pgrp=2
serverb:/srv/homes/alice on /remote/homes/alice type nfs4 (rw,relatime
serverb:/srv/homes/student on /remote/homes/student type nfs4 (rw,relatime

One map line served both; each directory appeared when used.

A direct map

Create a direct map so that /mnt/direct/data mounts serverb:/srv/shared. Reload autofs, use the path, and list the maps that autofs has loaded.

[root@servera ~]# echo '/-  /etc/auto.direct' > /etc/auto.master.d/direct.autofs
[root@servera ~]# echo '/mnt/direct/data  -rw  serverb:/srv/shared' > /etc/auto.direct
[root@servera ~]# systemctl reload autofs
[root@servera ~]# ls /mnt/direct/data
hello.txt
[root@servera ~]# automount -m | grep -E "Mount point|map:"
Mount point: /misc
  map: /etc/auto.misc
Mount point: /net
Mount point: /-
  map: /etc/auto.direct
Mount point: /remote/homes
  map: /etc/auto.homes
Mount point: /mnt/auto
  map: /etc/auto.shared

Make a user's home on the client

Create alice on servera with the same UID 2001 and write a file in her mounted home as alice. Check the owner on the server.

[root@servera ~]# id alice > /dev/null 2>&1 || useradd -u 2001 alice
[root@servera ~]# su - alice -c 'echo "edited from servera" >> /remote/homes/alice/readme; cat /remote/homes/alice/readme'
alice home
edited from servera
[root@serverb ~]# ls -ln /srv/homes/alice
total 4
-rw-r--r--. 1 2001 2001 31 Oct  3 19:05 readme

Grade and finish

Check your work with lab grade sa-nfs-maps, then put the exercise away with lab finish sa-nfs-maps.