Multiple Instances of Services

From Alpine Linux

Alpine makes it very easy to install and run a service, but what if you need to have multiple instances of the same service running on the same machine. For instance, what if you want to run split-DNS, where you respond to DNS requests differently for internal and external networks. The simple response is to run two instances of tinyDNS listening on two different Ethernet interfaces. Now, how do you do it? How do you manage the two instances once you have them running?

The following example is specifically for TinyDNS, but can be applied to other services as well. TinyDNS will work because the init.d script has been written in such a way as to allow multiple instances. The procedure is written for alpine 1.9, but should work for other versions as well.

Install The Service

First, we'll install TinyDNS and the ACF

# apk add acf-tinydns

This will install the TinyDNS service, as well as the ACF web interface used to manage the service. Having only one instance of TinyDNS, you can manage it from the console using /etc/init.d/tinydns, /etc/conf.d/tinydns, and /etc/tinydns/ or from ACF using the Networking > DNS pages.

Create a Second Instance of the Service

Now, we create a symlink to the TinyDNS init.d script for each new instance you want to run. (For alpine 1.8, you should not use the plain tinydns init.d script so that ACF can properly determine which instance is running, but create two new instances instead) We're going to create a second instance that will handle the internal network.

# ln -s tinydns /etc/init.d/tinydns.internal

Create conf.d and domain files for each new script. You can copy the tinydns files to start.

# cp /etc/conf.d/tinydns /etc/conf.d/tinydns.internal # cp -r /etc/tinydns /etc/tinydns.internal

You now have a second instance of the TinyDNS service that you can manage from the console using /etc/init.d/tinydns.internal, /etc/conf.d/tinydns.internal, and /etc/tinydns.internal/. But, how do you manage it with ACF?

Create a Second Instance of the ACF

Set up an ACF controller for the new script. Controller names can only contain letters, numbers, and '_'.

# mkdir /usr/share/acf/app/tinydns_internal

Set up the modified ACF code for each new script. Only three files must be modified, the others may be copied or symlink'd. The name of the controller must be changed to allow the ACF permissions of the two TinyDNS instances to be managed separately.

# cd /usr/share/acf/app/tinydns # for a in tinydns*; do cp $a /usr/share/acf/app/tinydns_internal/$(echo $a {{!}} sed "s/tinydns/tinydns_internal/"); done

# vim /usr/share/acf/app/tinydns_internal/tinydns_internal-model.lua

Change 'local processname = "tinydns.internal"'

# vim /usr/share/acf/app/tinydns_internal/tinydns_internal.roles

Replace each instance of 'tinydns' with 'tinydns_internal'

# vim /usr/share/acf/app/tinydns_internal/

Modifiy the main menu entry, ie. replace each instance of '30DNS' with '31DNS_Internal'

Once you log out and log back into ACF, you should see the new ACF pages and menu options available. User and role management can be handled separately for the new instance. (In alpine 1.8, users should not be given access to the plain TinyDNS ACF)

Save Your Changes

The /usr/share directory is not automatically included in lbu commits, so the new ACF instance must be added manually.

# lbu add /usr/share/acf/app/tinydns_internal

Then, commit the changes.

# lbu commit