Let's say you want to install and configure autofs so to have network fileshares mounted on demand. That sounds like a good task for Ansible.
Installing AutoFS
The installing part as you know is fairly easy. In both RedHat and Debian derivatives the package name is autofs. Since we are not doing anything special we can create a rather generic Ansible task using the Ansible package module. What that means is instead of having to worry about having a version for, say, Ubuntu and RedHat, the package module uses whatever package manager is the default for the distro in question:
- name: setup autofs
package:
name: autofs
state: latest
NOTE: I know package works in the redhat/debian derived distros, but I am not sure if it will work in other Linux flavours. I also would check the autofs package name for these other distros.
Configuring AutoFS
Next thing we want to do is ensure we are using the right NFS version. That is done finding the line beginning with mount_nfs_default_protocol and editing its value. In my case I want to make sure it is using NFS v4, which is the default anyway in a modern autofs package. So, why bother? Well, call me paranoid: I want to have exactly what I want. Or call it a simple example of using the Ansible lineinfile module. Or maybe someone is using NFS v3 and want to see how to change it.
- name: Ensure nfs v4
lineinfile:
path: /etc/autofs.conf
regexp: '^mount_nfs_default_protocol '
line: 'mount_nfs_default_protocol = 4'Let's use this as an excuse to talk about lineinfile: the regexp here is looking for a line that starts with the string 'mount_nfs_default_protocol '; I wrote it in quotes because it includes the blank space after mount_nfs_default_protocol. Note that the search pattern also means "and anything else to the end of the line," so a line looking like this
mount_nfs_default_protocol could be something you do not want to touch
is fair game. I know usually in regexp you would end the query statement with
(.*)$ to include everything to the end of the page, but just nod a lot and move on. Now if the looked like this:
#mount_nfs_default_protocol could be something you do not want to touch
the regexp would not work because it expects the line to begin with
m.
line defines what we want the line to look like. If it matches that, no changes made.
The next step is to define what we want to use autofs for. In my case, I want to mount user home directories off the fileserver. That means creating a /etc/auto.home file which describes which fileserver we are using. For this I suggest using the template module since we can define the name of the fileserver somewhere earlier in the playbook or in a config file (I am thinking here of a file in host_vars/ or group_vars/ associated with the host in question.). In my task file I use something like
- name: configure auto.home
template:
src: auto.home.j2
dest: /etc/auto.home
mode: 0644
owner: root
group: root
serole: _default
setype: _default
seuser: _default
notify: restart autofswhich
- Grabs the template templates/auto.home.j2 and puts it in /etc/auto.home
- Sets the permission, ownership, and selinux parameters for /etc/auto.home. The _default means that if there is a default selinux setting for that file/directory we will use it.
And roles/common/templates/auto.home.j2 looks like this:
/etc/auto.home
#
# File: /etc/auto.home
#
* -fstype=nfs4,hard,intr,rsize=8192,wsize=8192 {{ nfs_server }}:/home/&
where
nfs_server is the name of the nfs server defined somewhere else.
Now, there are two ways to deal with it, the old autofs and the new one.
- Old autofs: In the old days, you would edit the /etc/auto.master file, adding a line underneath +auto.master that would tell us how to mount user home directory. In the following example,
+auto.master
/home /etc/auto.home --timeout=300
the bottom line is saying "if you notice someone trying to access a file/directory in /home, go to /etc/auto.home to see how to mount it. But, if there is no activity after 300 seconds, unmount that." I use timeout of 300 seconds; change it to fit your needs. Now we need to add that to /etc/auto.master, which we will do using the lineinfile module once more:- name: Enable auto.home in auto.master
lineinfile:
path: /etc/auto.master
regexp: '^\/home'
insertafter: '^\+auto.master'
line: /home /etc/auto.home --timeout=300As you can see, it is a little more complex than the previous task:
- The regexp statement has to escape the /
- insertafter is used to look for a line which matches that pattern and then insert/change the line we want below this pattern. This is useful when you have more than one line matching the regexp pattern or you want the line we are creating/replacing to be on a specific location. You see, without that if line does not exist, it is appended on the end of the file.
- New autofs: The more modern /etc/auto.master file has the following lines in it:
#
# Include /etc/auto.master.d/*.autofs
# The included files must conform to the format of this file.
#
+dir:/etc/auto.master.d
#
Instead of editing the /etc/auto.master file, which might be overwritten by an upgrade, we simply throw a file inside the /etc/auto.master.d directory which is then loaded into the /etc/auto.master file. This file, say /etc/auto.master.d/home.autofs, looks very much like what we did in the old autofs example, main difference is that it is a file
raub@desktop:~/dev/ansible$ cat roles/common/files/home.autofs
/home /etc/auto.home --timeout=300
raub@desktop:~/dev/ansible$
that needs to be uploaded using the Ansible file copy module:- name: Enable auto.home in auto.master.d
copy:
src: home.autofs
dest: /etc/auto.master.d/home.autofs
owner: root
group: root
serole: _default
setype: _default
seuser: _default
mode: 0644
Which one to pick? You know your setup, so pick the one that fits your needs.
(Re)Starting autofs
The final step we do need to do is (re)start autofs service after all this configuring. We do that using handlers:
- name: start autofs
service:
name: autofs
state: started
enabled: yes
- name: restart autofs
service:
name: autofs
state: restarted
enabled: yesThe way I use them is to start autofs when package is installed (see the notify statement),
- name: setup autofs
package:
name: autofs
state: latest
notify: start autofsand then restart it after finishing with
auto.home- name: configure auto.home
template:
src: auto.home.j2
dest: /etc/auto.home
mode: 0644
owner: root
group: root
serole: _default
setype: _default
seuser: _default
notify: restart autofsAfter I unleash ansible, I then ssh as the non-root user which is allowed to login to vmhost2 and then see if fileshare was mounted:
[raub@vmhost2 ~]$ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 16G 0 16G 0% /dev
tmpfs 16G 0 16G 0% /dev/shm
tmpfs 16G 8.9M 16G 1% /run
tmpfs 16G 0 16G 0% /sys/fs/cgroup
/dev/mapper/vmhost-root 2.0G 71M 2.0G 4% /
/dev/mapper/vmhost-usr 4.0G 1.8G 2.2G 46% /usr
/dev/sda2 976M 179M 731M 20% /boot
/dev/sda1 200M 6.8M 194M 4% /boot/efi
/dev/mapper/vmhost-var 4.0G 376M 3.7G 10% /var
/dev/mapper/vmhost-vg_backup 10G 104M 9.9G 2% /var/lib/libvirt/qemu/save
fileserver.example.com:/home/raub 690G 629G 61G 92% /home/raub
tmpfs 3.2G 0 3.2G 0% /run/user/1001
[raub@vmhost2 ~]$
[raub@vmhost2 ~]$ systemctl status autofs
● autofs.service - Automounts filesystems on demand
Loaded: loaded (/usr/lib/systemd/system/autofs.service; enabled; vendor pres>
Active: active (running) since Mon 2019-12-09 14:17:26 EST; 2min 39s ago
Main PID: 28387 (automount)
Tasks: 6 (limit: 26213)
Memory: 3.3M
CGroup: /system.slice/autofs.service
└─28387 /usr/sbin/automount --foreground --dont-check-daemon
[raub@vmhost2 ~]$I do not know about you but it seems we have a winner. I will put a cleaner version of this playbook and supporting files in my github account later on.
