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Table of Contents

• Preparing the disk
• Mounting the disk
• Installing netatalk
• Configuring Netatalk

This is a simple guide on building a $35 Time Capsule with a Raspberry Pi. A Time Capsule is a network attached storage device from Apple for use with their Time Machine. Time Machine gives users a very easy and userfriendly way to automatically create and restore (encrypted) backups. A Time Capsule is basically an expensive NAS that only talks the AFP/netatalk protocol. The 2 TB version costs $299 at this time, a Raspberry Pi only $35.

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You will need the following:

• Raspberry Pi, Model B/B+
• USB Hard Disk / Big USB Dick

The Raspberry Pi can run either Raspbian or Arch, this guide works on both. The USB storage works best if it is externally powered.

I've tested with 2 different Raspberry Pi's, one model B+, raspbian, with a 128GB USB disk (from Sandisk) and on Raspberry Pi Model B with Arch and a 1 TB USB hard drive. I've got some spare disk lying around, if you don't you should buy one. The total cost might be higher than $35 if you need to buy storage or want a nice case and other accessories.

Preparing the disk

Make sure the Pi is installed with your OS of choice (Raspbian or Arch). Plug the USB drive in. We will first format it to a big EXT4 partition.

Install cfdisk first, or just use parted/fdisk if you know the drill.

Debian:

apt-get install cfdisk

Arch:

pacman -Sy cfdisk

Issue the dmesg command and look at the last few lines. Remove the USB storage and re-attach it. Execute the dmesg command again and look for lines like this:

[ 7793.698383] usb 1-2.4: USB disconnect, device number 11
[ 7798.233788] usb 1-2.4: new high-speed USB device number 12 using xhci_hcd
[ 7798.326648] usb-storage 1-2.4:1.0: USB Mass Storage device detected
[ 7799.331790] sd 3:0:0:0: [sdb] Attached SCSI removable disk

Here you can see that /dev/sdb is our newly attached disk. Change it to your setup. Be carefull with this, any typo's might erase all your OS data. Format it with cfdisk:

cfdisk /dev/sdb

Delete all partitions on there and create on big Linux (83) one. Do note that this will remove all data on the disk.

If you have a big disk (> 2 TB) you might need to create a GPT table on it. Use parted for that:

parted /dev/sdb
mklabel gpt
unit s
mkpart primary 2048s 100%
name 1 BFS
quit

Now create an ext4 filesystem on it:

mkfs.ext4 /dev/sdb1

Proceed to mounting the disk.

Mounting the disk

We add the disk to /etc/fstab to make sure it will still be mounted after a reboot. Otherwise you might end up with a full Pi and we don't want that.

Edit /etc/fstab:

vim /etc/fstab

Add the following to it, change the disk device path if it is different:

/dev/sdb1   /mnt/data  ext4    noexec,defaults  0   0

Create the actual mount folder:

mkdir -p /mnt/data

Mount it, via fstab:

mount -a

Now check the df -h command and see if it is actually mounted.

Installing netatalk

netatalk is the program that talks the AFP protocol, which is wat Apple uses for Time Machine. Install the daemon,

For Debian:

apt-get install netatalk

For Arch

pacman -Sy netatalk

Note that on Arch Linux Arm the AUR is included as a repo by default. If you run it on regular arch you need to use yaourt to install netatalk or build netatalk from the AUR yourself.

Make sure the service starts at boot:

Debian:

update-rc.d netatalk defaults

Arch:

systemctl enable netatalk

Configuring Netatalk

Edit the file /etc/afp.conf:

vim /etc/afp.conf

Place the following contents. Edit the path's, user names and IP range:

[Global]
 mimic model = TimeCapsule6,106
 log level = default:warn
 log file = /var/log/afpd.log
 hosts allow = 196.168.1.0/24

[Homes]
 basedir regex = /home

[TimeMachine]
 path = /mnt/data/timecapsule/
 valid users = tmuser wife remy
 time machine = yes

[Shared Media]
 path = /mnt/data/torrents/
 valid users = wife remy

Do not use a symlink as the source of this file. netatalk will not work correctly.

I also share a folder with my Transmission Torrents in there, that contains about 400 GB of Linux iso's. The OS X machine is the only machine with a DVD burner in the house, therefore I use that to burn them to disk.

The config file itself it pretty self explainatory.

Make sure the folders actually exist. Create them with:

mkdir -p /mnt/data/{timecapsule,torrents}

Restart the netatalk service:

Debian:

service netatalk restart

Arch:

systemctl restart netatalk

On Arch you might need to configure the Avahi service, on Arch Linux Arm it is enabled by default. This provides Bonjour capabilities.

You might need to create a user or set the correct permissions on the folder. I'll add the user wife to the Pi, put her in the users group and give the users group write permissions on the folders we share via AFP.

Add the user wife:

useradd wife

Set the password for wife:

passwd wife

Create the users group:

groupadd users

Add the user to the users group:

usermod -aG users wife

Set the correct permissions on the time machine folder:

chown remy:users /mnt/data/timecapsule 
chmod 775 /mnt/data/timecapsule

That's it. You can now configure Time Machine on OS X. Search for the folder, it should pop up:

Enjoy your $ 35 Time Capsule. Consider making a donation with (a part of) the money you saved. Or if you like this article and want to support me AND get $10 Digital Ocean credit (2 months free), use this link to order: https://www.digitalocean.com/?refcode=7435ae6b8212

Tags: apple , arch , articles , backup , debian , os-x , raspberry-pi , time-capsule , time-machine