Raspberry Pi Zero Cookbook

The GPIO header is the same one you will find on the Raspberry Pi B and later versions. The big difference here is that a header hasn't been soldered on. If you project requires your Raspberry Pi to be very thin, then you can solder your connections directly to the board. If you are using your Zero for prototyping, you can attach whichever header makes your life easiest. For this book, we will have the female 90-degree header soldered on for easy interfacing to the Adafruit Pi Cobbler.

The Micro SD card slot is very much the same as previous versions, with the big difference being that it is push-in/pull-out instead of other boards' push-in/push-out slot.

The mini-HDMI port works just like a regular-sized port, though it requires an HDMI mini-to-regular adapter or cable to connect to LCD monitors.

The first USB port is micro-USB, and the only USB port available for data use on the Raspberry Pi Zero. For use with standard USB components such as mice and keyboards, you will need a micro-USB OTG adapter and a powered USB hub. As we move forward in the book, we will discover ways to run "headless" so that not all the connections are required, but to get started, you will want an adapter and a hub.

The second USB port is the Raspberry Pi's power connection, which we will take a closer look at in the next recipe.

This bus is to attach the Raspberry Pi's camera cable.

While RCA video is no longer available on the Raspberry Pi Zero, we will hack it later to understand how to use the older, non-HDMI way to see video.

Finally, on this side of the board, the connectors marked RUN are for resetting the Raspberry Pi. Shorting these connections will reset your Raspberry Pi.

Open a Terminal window in OS X.

Next, run shasum against the downloaded ZIP file to validate the signature:

$ shasum ~/Downloads/2016-05-27-raspbian-jessie.zip 
64c7ed611929ea5178fbb69b5a5f29cc9cc7c157
    /Users/ed/Downloads/2016-05-27-raspbian-jessie.zip

The Raspbian Jessie download and SHA-1 signature

If the return value matches the SHA-1 signature provided on the Raspberry Pi downloads page, your file is good and can be unzipped:

$ unzip ~/Downloads/2016-05-27-raspbian-jessie.zip 
Archive:  /Users/ed.snajder/Downloads/2016-05-27-
    raspbian-jessie.zip
inflating: 2016-05-27-raspbian-jessie.img  

Next, look at the filesystem before inserting the SD card:

$ df -h
Filesystem      Size   Used  Avail Capacity  iused 
    ifree %iused  Mounted on
/dev/disk1     232Gi  216Gi   16Gi    94% 56751574 
    4163032   93%   /
devfs          205Ki  205Ki    0Bi   100%      710 
    0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%        0 
    0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%        0  
    0  100%   /home
map -fstab       0Bi    0Bi    0Bi   100%        0  
    0  100%   /Network/Servers

Then, insert the SD card and run the command again:

$ df -h
Filesystem      Size   Used  Avail Capacity  iused 
    ifree %iused  Mounted on
/dev/disk1     232Gi  216Gi   16Gi    94% 56751576 
    4163030   93%   /
devfs          211Ki  211Ki    0Bi   100%      730 
    0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%        0  
    0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%        0 
    0  100%   /home
map -fstab       0Bi    0Bi    0Bi   100%        0 
    0  100%   /Network/Servers

/dev/disk2s6    63Mi   20Mi   43Mi    32%      512 
      0  100%   /Volumes/boot


/dev/disk2s1   1.1Gi  1.0Gi   92Mi    92%        0 
      0  100%   /Volumes/RECOVERY

As you can see, /dev/disk2s6 and /dev/disk2s1 were added. This creates two partitions on disk2 - most SD cards will only have one, but however many there are mounted, you need to unmount them with diskutil:

$ sudo diskutil unmount /dev/disk2s1
Password:
Volume RECOVERY on disk2s1 unmounted
$ sudo diskutil unmount /dev/disk2s6
Volume boot on disk2s6 unmounted

There is a critical difference now from typical Linux drives and dd use. Let's say you had the aforementioned configuration and see that the SD card disk is disk2. For the dd command, you will change this to rdisk2:

$ sudo dd bs=1m if=./2016-05-27-raspbian-jessie.img 
    of=/dev/rdisk2

3833+0 records in
3833+0 records out
4019191808 bytes transferred in 377.097088 secs (10658241 bytes/sec)

Finally, eject the disk, and you are ready to go!

$ sudo diskutil eject /dev/rdisk2
Disk /dev/rdisk2 ejected

I find the easiest method is to look at what is mounted. If the SD card is inserted, it should be automatically recognized:

$ mount -l

Another way to find the mount(s) on the SD card is looking using the dmseg command. Ubuntu's documentation recommends using dmesg to find out which device the SD card is. Insert the SD card and run this:

$ dmesg | tail -20

You'll get a response similar to this:

dmesg output after SD card insertion

Before overwriting, you need to detach the disks that are mounted. In this case, sdd1 and sdd2 are the mounted partitions for device sdd, as shown in the last line of the image above.

In Linux, your disk devices are usually identified by looking in the /dev/ folder for devices starting with sd (for example sda, sdb, sdc). A partition is a division of the physical volume so it can be treated as different devices, and they can be identified by having incremental numbers (for example sdd has partitions sdd1 and sdd2):

$ sudo umount /dev/sdd1
$ sudo umount /dev/sdd2

After downloading the latest ZIP file of the Raspbian image from the Raspberry Pi website, you can validate it using the sha1sum tool:

$ sudo sha1sum ~/Downloads/2016-05-27-raspbian-
    jessie.zip
64c7ed611929ea5178fbb69b5a5f29cc9cc7c157
   /media/sf_Downloads/2016-05-27-raspbian-jessie.zip

If your return value matches the SHA-1 value on the Raspberry Pi Downloads page, unzip the file, and run the dd command to write your image to the SD card. Make sure you are using the correct device!

The dd command is for entire disks, so we reference sdd instead of the partitions sdd1 or sdd2. We don't want to duplicate things to partitions, we want to duplicate the entire disk, and whatever partitions your source has will be applied to the destination, our SD card.$ sudo dd bs=1M if=/path/to/raspbian-jessie.img of=/dev/sdd

The TV pins in the figure are the connections you can use to connect RCA video to the Raspberry Pi:

Raspberry Pi Zero RCA video

Solder wires or connectors here that will connect to the RCA video plug.

Confirm that the SD card is inserted and that your video and USB connections are set, and connect the micro-USB power to an adapter. If you started with NOOBS, you will be taken to the OS selection screen. Right now, there isn't very much to select from. The primary reason is that the Raspberry Pi Zero doesn't yet have Internet capability, so a list of available operating systems cannot be retrieved. For now, it is as easy as clicking on the checkbox for Raspbian and the Install button in the top left. From there, you are a few minutes from your new Raspberry Pi Zero desktop!

Once you click on Install, NOOBS takes care of the rest and sets up a brand new default Raspbian system on your SD card. The system will start quickly and take you right to the installation screen:

NOOBS OS selection screen

When you select Install, NOOBS will take care of the rest and prepare your card with the Raspbian operating system:

NOOBS Raspbian setup

After this is complete, the installer will have you click to reboot, after which you will be taken right into Raspbian.

After you select Finish on the raspi-config tool, it will ask whether you'd like to reboot. Select Yes, and the Raspberry Pi Zero will begin its power-down process. When it starts back up, it will take you right back to the Raspbian desktop. You can reboot the Pi anytime with this command:

sudo reboot now

Boot Options: After your reboot completes, reopen the Terminal screen and run sudo raspi-config again. Select the third option, Boot Options. There are four different boot mode options to choose from:

The Boot Options menu

Here, you can choose to start the Raspbian desktop or just boot into a command-line interface. It also gives you choices on requiring logins or not; if automatic login is chosen, you won't need to enter the password, so if you want a little bit of security, select one of the options that require the user to log in. My preference is Text console, requiring user to login, because it gives you a bit of security and requires less CPU and memory than running the desktop. If I need the desktop, it is simple to start it with startx. You can do a lot with Linux just from the command line, so a lot of the time, the desktop GUI isn't necessary.

Overclocking: Option 8, Overclocking, returns a rather un-fun message to the user. I'm not sure whether this is the latest version of Raspian's raspi-config program or whether it applies to both the Raspberry Pi Zero and the Raspberry Pi 3, but the same message was returned on both.

An attempt to overclock from raspi-config does not return an optimistic response:

No overclock for you!

It was discovered in late 2015 that overclocking options on the Raspberry Pi Zero only caused it to slow down, so the latest version of raspi-config does not assist with overclocking. This doesn't mean it is impossible, however-just not advised.

Open the following file:

$ sudo grep arm /boot/config.txt
#uncomment to overclock the arm. 700 MHz is the 
     default.
#arm_freq=800 

This does hint that overclocking is still possible at startup using the config.txt file. Commenting out arm_freq=800 in the /boot/config.txt file to a higher frequency should work, although the Raspberry Pi community suggests that it doesn't, and perhaps even reduces performance. Even more interestingly, looking at the running settings of a Raspberry Pi Zero suggests that it is already being overclocked to 1 GHz, compared to the former setting of 700 MHz on older Raspberry Pi models:

$ cat
     /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
1000000
$ cat
     /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
1000000
$ cat
      /sys/devices/system/cpu/cpu0/cpufreq/
      scaling_available_frequencies
700000 1000000

This output suggests that it is already running at 1 GHz and has options to run from 700 MHz to 1 GHz. You can play around with overclocking, and I suppose it was possible to push the B+ Pis to the 1.1 GHz range-you will probably see too much instability from setting it to anything much higher than that. If it becomes unusable, you should be able to recover by commenting out your arm_freq change in the config.txt file from a stable machine. Now let's work on creating new users:

Creating new users is very easy on Raspbian. Here, we will create one named rpz with a home directory located in /home/rpz:

pi@raspberrypi:~ $ sudo adduser rpz --home /home/rpz
Adding user `rpz' ...
Adding new group `rpz' (1002) ...
Adding new user `rpz' (1002) with group `rpz' ...
Creating home directory `/home/rpz' ...
Copying files from `/etc/skel' ...
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for rpz
Enter the new value, or press ENTER for the default
        Full Name []: Raspberry Pi Cookbook
        Room Number []:
        Work Phone []: 123-456-7890
        Home Phone []: 234-456-7890
        Other []:
Is the information correct? [Y/n] y

This will create the new user's home directory and prompt you for the password. Once you have this set up, you can log on as this user. This will give the user their own home directory in /home/username and the ability to execute applications. The users are stored in a file called /etc/passwd.

To look at your user, you can look at the end of this file:

pi@rpz14101:~ $ cat /etc/passwd | tail -5
lightdm:x:109:114:Light Display 
      Manager:/var/lib/lightdm:/bin/false
pulse:x:110:116:PulseAudio 
      daemon,,,:/var/run/pulse:/bin/false
rtkit:x:111:118:RealtimeKit,,,:/proc:/bin/false
ed:x:1001:1001::/home/ed:/bin/bash
rpz:x:1002:1002:Raspberry Pi Cookbook,,123-456
     -7890,234-456-7890:/home/rpz:/bin/bash

The last entry is the user just created:

rpz:x:1002:1002:Raspberry Pi Cookbook,,123-456-
      7890,234-456-7890:/home/rpz:/bin/bash