Mac OS X "hosts" file, can I include other files with it?

Question

I am working on some automation scripts to configure my network settings, hosts file contents, and /etc/resolver files, when accessing different networks I frequent between.

There are some combinations that can occur that all require changes to the hosts file, and I'd like to avoid having to set up a matrix of different combinations, duplicating the shared settings all over the place.

For instance, I may be on the work network, ie. in the building, or I may access it over VPN. In both cases, I need to add some settings to the hosts file for networking to work properly, some are shared, some are not. Additionally, if I'm over VPN, I may be at home, in which case there are some other settings in the hosts file I also want to add.

As such, I was hoping that instead of creating one file for "home, accessing work over VPN" vs. "home, not accessing work", etc., is there a way for me to include other files?

For instance, let's say the following hypothetical syntax works:

#!include home.hosts
#!include work.hosts

127.0.0.1 localhost
::1 localhost

This way, I could simply clear out the contents of one, or both, of those two extra files, and leave the rest be.

Or, barring that, is there a better way to do this than to just build a small script that concatenates files such as those into a new hosts file, and as part of my automation setup, I first clear out some of those extra files, and then I invoke the script to rebuild the single hosts file from those extra files?

Answer 1

I am not aware of any include possibility. What I'd do, however, is to make sections in my hosts file, and then use a script to comment the lines in each section using, e.g., sed.

This way your file would look like

#%%%HOME.HOSTS%%%
#Put here the contents of home.hosts
#%%%WORK.HOSTS%%%
#Put here the contents of work.hosts

#%%%ALWAYS_ON%%%
127.0.0.1 localhost
::1 localhost

Edit: Adding in a quick attempt to modify the fields.

Removing the comment for HOME.HOSTS

 sed -i '/#%%%HOME.HOSTS/,/#%%%/s/^#\([^%]\)/\1/g' hosts

Putting back the comments for HOME.HOSTS

 sed -i '/#%%%HOME.HOSTS/,/#%%%/s/^\([^#]\)/#\1/g' hosts

This is a basic version, and needs to be adjusted to your needs.

Answer 2

Since dscl is no longer working due to the switch to OpenDirectoryService, one option is to use ghost:

sudo gem install ghost

sudo ghost add fw.test.se 10.0.0.1

...will add this section in the /etc/hosts:

# ghost start
10.0.0.1 fw.start.se
# ghost end

To clear the #ghost section of the hosts file use (this makes it easy to replace the list of hosts with a new one):

sudo ghost empty

You can find more information about ghost here: https://github.com/bjeanes/ghost

Answer 3

I had a similar use case when I needed to access services on three different places using different LAN / WAN settings in hosts file. Karolos' answer above is one possible solution. My approach is here.

1- ref to http://apple.stackexchange.com/q/139267/74657

2- created hosts files for each location (hosts.work, hosts.home, hosts.vendor)

3- Using soloz's script, here (https://github.com/slozo/Network-listener) whenever I connect to home network, I execute simple script to switch the hosts file.

simplest method would be

mv hosts.home /etc/hosts

alternately you can automate Karolos' answer above using sed to update the exiting file on connecting to specific SSID which you can detect and run easily by using soloz's script mentioned above.

hope that helps anyone stumbling upon the subject issue.