Wednesday, November 16, 2011

Using a Scientific Linux/CentOS/RHEL 6 Server for Time Machine

I recently tried to setup a Scientific Linux 6 server as a backup volume for Time Machine. I based my steps on these instructions for Ubuntu, but I thought there was enough differences that I thought it was worth posting what worked for me. I used Scientific Linux 6, but it should work just as well for CentOS 6 and Red Hat Enterprise Linux 6.

A few assumptions made in these instructions, you will want to replace them as appropriate:
  • The user's username is "user".
  • The Linux server has a hostname of "". If you don't have a hostname in DNS, you can use the server's IP address instead.

First, we need to setup the server:

1. Install the EPEL repository. I already had it on the machine, but if it's not yet installed, read and follow the instructions at

2. Install netatalk from the EPEL repository:
# yum install netatalk

3. Add the following line to the end of /etc/netatalk/afpd.conf:
- -transall -uamlist, -nosavepassword -advertise_ssh

4. Create the TimeMachine directory in the user's home directory or wherever you want it:
$ mkdir /home/user/TimeMachine

5. Add the following two lines to the end of /etc/netatalk/AppleVolumes.default. Note that I commented out the ~ line that was already present since I didn't want to enable home directory access; I just want to use this for Time Machine:
/home/user/TimeMachine TimeMachine allow:user cnidscheme:dbd options:userdots,upriv

6. Configure netatalk to be started when the system boots:
# chkconfig netatalk on

7. Start netatalk:
# service netatalk start

8. Open the AFP port in the firewall. Go to System, Administration, Firewall. Click Other Ports, Add, then scroll down until you find Port 548, Protocol tcp, Service afpovertcp. Select it and click OK. Repeat for Port 548, Protocol udp, Service aftpovertcp. Click Apply, then close the Firewall Configuration window.

Now, on your Mac:

1. Verify that you can connect to the server. From the Finder's Go menu, choose Connect to Server. Enter the server address afp:// and click Connect. You should be prompted for a username and password.

2. Configure Time Machine to allow you to use network volumes for Time Machine. Enter the following command in
$ defaults write TMShowUnsupportedNetworkVolumes 1

3. Go to System Preferences, select Time Machine. Enable Time Machine and select your mounted TimeMachine volume. You will be prompted for a username and password that Time Machine will use to connect when it's performing the backup.

Friday, March 18, 2011

Why AT&T Should Give Me a 93% Discount on U-Verse Internet

So, I recently moved. At my new house, I signed up for AT&T U-Verse TV and Internet. So, what happens this week, before I've even received my first bill? DSLReports and Engadget break the news that AT&T will begin imposing a 250 gigabyte per month cap on U-Verse Internet service. This already has me reconsidering my options.

Switching to DSL (I've heard a lot of good things about DSLExtreme) would be my likely choice, as I've had some pretty bad experiences with Time Warner Cable's Internet offerings. Plus, from what I understand, DSL and U-Verse run over the same copper pair, so I'd also have to change my TV provider. Time Warner Cable isn't all that attractive, and I had some bad experiences with the DirecTV customer service people before deciding on U-Verse. But that's really beside the point, and not why I'm breaking out the Blogger account for the first time in almost a year.

No, I want to lay out why AT&T should be giving me an 93% discount on my U-Verse service. It all boils down to simple math:

I have the U-Verse Max plan, which offers download speeds of 12 megabits per second. I even did the math in AT&T's favor, and used a non-leap year February as the definition of a month, being 28 days. Now we need to do one more division:

In other words, the bandwidth caps allow me to use just 7% of the theoretical maximum amount of Internet usage I could have in a month. And that doesn't account for the 1.5 megabits per second upload speed. So if I can only get 7% of what I signed up for, I should only pay 7% of what I was paying for before. In other words, a 93% discount.

Since the current charge for U-Verse Max is $45/month, that means I'll be paying just $3.15/month if I were to get the discount. Oh, and the folks with the $65/month Max Turbo plan, which offers 24 megabits per second? They'll barely get 4% of what they signed up for. It actually makes Max Turbo the an even better deal, at a mere $2.60/month.

Figuring out how long it would take at 12 megabits per second to consume the 250 gigabyte per month limit is left as an exercise to the reader. It's simple middle school algebra.