I realized over the weekend that since I run my own mail server out of my home, I can configure my computer to download my mail over the intranet whenever I am on my home network. By doing this, I can drastically reduce my mail download times because it cuts the Internet out of the equation. Rather than using DNS + the Internet to get my mail, I can download it directly from internal IP address of the server.
To understand how to set this up, you have to understand that whenever you use a domain name (like michaeljaylissner.com), your computer does an IP lookup. First, it looks in /etc/hosts to see if it knows the IP of the domain locally. If it does, it will use the IP listed there. If it does not, it will ask your Internet provider what IP to use, and will use that. Thus, what we want to do is set up the computer so that when we are at home, /etc/hosts provides the internal IP of our server, and so when we are not at home, it does not.
When I am at home, I am always on a wireless network called,
pizzapuppysantaclaus. Thus, by checking what wireless network I am
connected to, I can check if I am at home, and make whatever changes are
necessary. Conveniently, whenever you change network connections,
you run all of the scripts located in
we will put a small script in there that checks what wireless network we are
on, and then changes our /etc/hosts file if necessary.
To set up this configuration, I made three files. The first is the script
mentioned above, which needs to be owned by root,
and placed in
/etc/network/if-up.d. You can name it whatever you want,
and by changing
pizzapuppysantaclaus to the name of your network,
you can fit it to your needs. Here’s the contents of the script:
#First, we check if we are connected to pizzapuppysantaclaus #If grep has a hit, we're connected, and $? will equal 0, if not, $? will equal 1 iwconfig 2> /dev/null | grep pizzapuppysantaclaus > /dev/null if [ $? = 0 ] then #Switch the /etc/hosts file with the other one cp -f /etc/hostsIntranet /etc/hosts else #Switch the /etc/hosts file with the other one cp -f /etc/hostsInternet /etc/hosts fi exit 0
This script simply performs a check of our wireless ID. If it’s
pizzapuppysantaclaus, it switches
not, it switches
The contents of
192.168.1.132 michaeljaylissner.com 192.168.1.132 charityhikers.org 127.0.0.1 localhost 127.0.1.1 opal # The following lines are desirable for IPv6 capable hosts ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters ff02::3 ip6-allhosts
/etc/hostsInternet is just a copy of
So, to make this whole thing run, put the script in
and set its owner to root with execute permission. Create a file called
/etc/hostsIntranet, that contains your intranet configuration,
as shown above. Make a copy of your normal
/etc/hosts file called
Once all that’s done, you should be all set. Any questions, please feel free to comment!
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