Time Machine (Mac OS 10.8.2) at Ubuntu 12.04

You want to use Time Machine over WIFI? - Then you have to buy a Time Capsule or you run a Time Machine at Ubuntu.

Tested with iOS 10.8.2 and Ubuntu Server 12.04

You did an unsuccessful installation before?

For the case that you did, remove Netatalk and all configuration files:

sudo apt-get remove --purge netatalk

Preparing the Ubuntu server...

From the Terminal (press ⌘ + SPACE and type terminal) you have to run the following command to install Netatalk:

sudo apt-get install netatalk

Note: See also Netatalk HTML documentation for more details.
Configure the afpd server:

sudo vi /etc/netatalk/afpd.conf

Add the following line at the end of this file:

- -tcp -noddp -uamlist uams_dhx.so,uams_dhx2_passwd.so -nosavepassword

Check if CNID_METAD_RUN=yes in "/etc/default/netatalk" file. Otherwise change it. Create a new user for the Time Machine connect:

sudo adduser username

Go to the newly created user directory and create a backup folder there:

cd /home/username/
mkdir time_backup
sudo chown -R username:username time_backup

Configure the newly created backup directory in Netatalk:

sudo vi /etc/netatalk/AppleVolumes.default

At the end of the file you add the following entry:

/home/username/time_backup "My Time Machine Backup" allow:username cnidscheme:dbd volsizelimit:250000 options:usedots,upriv,tm

Make sure that you adjust the directory and username to your needs. With "volsizelimit" you can define the maximum size of the backup. In this case 250 GB.

After you are finished with all the configuration staff you need to restart the Netatalk service:

sudo service netatalk restart

Don't forget to allow afp if you are using ufw - Uncomplicated Firewall:

# Allow network access to the ports 548 and 427
sudo ufw allow 548
sudo ufw allow 427
sudo ufw disable && sudo ufw enable 

Preparing the Mac client...

To allow unsupported network volumes, you have to run the following command in Terminal (press ⌘ + SPACE and type terminal):

defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1

"Connect to your server" (open Finder and press ⌘ + K) and type the address of your server:

afp://ip_address

Congrats, your Ubuntu server volume should be visible and ready for Time Machine usage now.