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Installing Ubuntu Server on Raspberry Pi – Headless

Raspberry Pi 2 Model B+ v1.1This article will describes the steps to install Ubuntu Server 16.04 on a Raspberry Pi 2. This article provides extra steps so that no screen or keyboard are required on the Raspberry Pi, it will be headless. But of course you need a screen and keyboard on the computer on which you will download the image and write it to the MicroSD card. It is similar to a previous article about installing Debian on Raspberry Pi 2, also headless mode.

Disclaimer: you need to know a minimum about computer, operating system, Linux and Raspberry Pi. If you just want to install an Operating System on your Raspberry Pi, get NOOBS the Raspberry Pi Foundation installer. This guide is for more advanced users. If you follow this guide but do mistakes, you might wipe out disk content or could even brick Micro SD card or what not.

Install the Ubuntu Server image

Ubuntu Circle of Friend LogoGrab your official Ubuntu Server for Raspberry Pi 2 image (the latest version at time of writing is ubuntu-16.04.1-preinstalled-server-armhf+raspi2.img.xz but in a few days the image for Ubuntu 16.04.2 should be available, it will save you some time when upgrading it (and save some write cycles on your Micro SD card). Once downloaded, you need to insert the Micro SD card on your computer (you probably need a USB card reader for that) and try to figure out which device it corresponds to, see the Ubuntu documentation for further guidance. I assume you know what you do but be weary that the next command if done on the wrong device could wipe out the data on that device. I do not take any responsibility if things go wrong.

$ xzcat ubuntu-16.04.1-preinstalled-server-armhf+raspi2.img.xz | dd of=<device> bs=32M

Create a user account and allow SSH access

Then make sure to sync your media data and then mount the newly created partition (normally there are 2 partitions created, we are interested in the second one, it should be named <device>p2 or <device>2:

$ sudo sync
$ sudo mkdir -p /mnt/rpi
$ sudo mount <device>2 /mnt/rpi

User account creation

As the Raspberry Pi uses an ARM processor and the computer on which I created the Micro SD card is a x86_64 processor, I cannot simply chroot and execute adduser in the newly mounted partition. The programs are compiled for a different architecture. So to add a new user we will need to do it manually by editing system files. We will create a new user and group, then add the corresponding entries in the files where the passwords are kept.

Add a new user (replace $(whoami) by your username if you want a different username than your current one).

$ echo "$(whoami):x:1000:1000:<Full Name>:/home/$(whoami):/bin/bash" | sudo tee -a /mnt/rpi/etc/passwd

Now create your group by editing /mnt/rpi/etc/group:

$ echo "$(whoami):x:1000:"" | sudo tee -a /mnt/rpi/etc/group

Now edit the group password database:

$ echo "$(whoami):*::$(whoami)" | sudo tee -a /mnt/rpi/etc/gshadow

And the user passsword database (it will have no default password but allow SSH key base authentication over the network and it will request to set a password upon first login. Note that with this configuration remote SSH login cannot happen without the SSH key, so it is a secure configuration):

$ echo "$(whoami)::0:0:99999:7:::" | sudo tee -a /mnt/rpi/etc/shadow

Grant your user access to administrative tasks (via sudo), but still requires that the user enter his own password:

$ echo "$(whoami) ALL=(ALL) ALL" | sudo tee /mnt/rpi/etc/sudoers.d/20_$(whoami)_superuser

User home folder and SSH access

Now we shall create the user’s home and add the SSH public key so we can login (it is assumed that you have a public RSA key under your home directory named ~/.ssh/id_rsa.pub change the name if it’s different):

$ sudo cp -R /mnt/rpi/etc/skel /mnt/rpi/home/$(whoami)
$ sudo chmod 0750 /mnt/rpi/home/$(whoami)
$ sudo mkdir -m 0700 /mnt/rpi/home/$(whoami)/.ssh
$ cat ~/.ssh/id_rsa.pub | sudo tee -a /mnt/rpi/home/$(whoami)/.ssh/authorized_keys
$ sudo chmod 0600 /mnt/rpi/home/$(whoami)/.ssh/authorized_keys
$ sudo chown -R 1000:1000 /mnt/rpi/home/$(whoami)

Setup Systemd for enabling SSH access and headless mode

Normally everything else should be correctly setup. However you might want to have a look at systemd configuration, mostly of interests are which default target is in use (for headless you want multi-user.target) and if the SSH service is part of the default target. What I did was the following (it also avoid creating the ubuntu user):

$ cd /mnt/rpi/lib/systemd/system
$ rm -f default.target
$ ln -s multi-user.target default.target
$ cd /mnt/rpi/etc/systemd/system/multi-user.target.wants
$ ln -s /lib/systemd/system/ssh.service ssh.service

(if the last command fails because the file already exist then it is all OK)

Start Ubuntu Server on Raspberry Pi

Now unmount the card and eject it: sudo umount /mnt/rpi. You can now safely insert the card in your Raspberry Pi 2 and boot it. It boots slower than with Raspbian, so be patient. Note that with all the above configuration, you do not need to boot with a keyboard or screen attached to your Raspberry Pi. Only an Ethernet cable and the power plug are necessary.

Now you need to find your newly installed Ubuntu Server on your network, the default hostname is ubuntu so you could always start with that (ssh $(whoami)@ubuntu) if it is not in conflict with another device of yours and if your router is clever enough to have updated the DNS resolver. Or else you need to scan your network for it. To scan your network you need to know your subnet (e.g. 192.168.1.0 with a netmask of 255.255.255.0) and have nmap installed on your computer (sudo dnf install nmap will work for Fedora, and it is as easy for Debian/Ubuntu-based distros as well, just replace sudo apt-get install nmap).

$ sudo nmap -sP 192.168.1.0/24

Of course you need to adapt the above command to your subnet. The “/24” part is the netmask equivalent of 255.255.255.0. I recommend running the above command with sudo because it will display the MAC address of all the discovered devices which will help you spot your Raspberry Pi as nmap is displaying the vendor attached to each MAC address. See for yourself in the example output:

Starting Nmap 6.47 ( http://nmap.org ) at 2015-07-19 20:12 CEST
(...)
Nmap scan report for ubuntu.lan (192.168.1.9)
Host is up (0.0060s latency).
MAC Address: B8:27:EB:1E:42:18 (Raspberry Pi Foundation)
(...)
Nmap done: 256 IP addresses (8 hosts up) scanned in 2.05 seconds

Now you can simply connect to your RPi using SSH:

ssh $(whoami)@192.168.1.9
Enter passphrase for key '~/.ssh/id_rsa':
You are required to change your password immediately (root enforced)
Welcome to Ubuntu 16.04.1 LTS (GNU/Linux 4.4.0-1017-raspi2 armv7l)

(...)

142 packages can be updated.
69 updates are security updates.

(...)

WARNING: Your password has expired.
You must change your password now and login again!
(current) UNIX password:

Now that you are authenticated and have access to your newly installed Ubuntu Server, it is time to upgrade it.

Upgrade Ubuntu Server to latest packages

The tool tmux should already be installed on your system (or do sudo apt install tmux), so use it to create a new session, so even if you get a network problem your session is not killed (simply do tmux attach)

$ tmux
$ sudo apt dist-upgrade
$ sudo systemctl reboot

Note: it is possible that unattended-upgrade kicks in before you can do the upgrade manually. Then wait an hour or more (depending on the speed of your internet connection and Micro SD card mainly) before doing the above steps. It is still worth while as the dist-upgrade command will perform more thorough upgrade (potentially removing deprecated packages or even downgrading some if necessary) but you will be in sync with the latest and greatest Ubuntu Server.

Picture credits: Photo of a Raspberry Pi board by me, see the website licensing policy. Ubuntu Circle of Friends logo is copyright by Canonical.

Installing Raspbian Headless (no screen, full network)

I’m going to explain how to install Raspbian (latest is based on Debian Wheezy, dated 2015-05) on a Raspberry Pi which is only connected to the network using a Ethernet cable (of course your Raspberry Pi should be connected to a power source).

Raspberry Pi 2 Model B+ v1.1This guide should work for all Raspberry Pi supported version with an Ethernet interface (B, B+ and 2). It could potentially work without an Ethernet interface if you have a WiFi USB dongle which is supported out-of-the box by the RPi. I’ve tested the following on a Raspberry Pi 2. This guide assumes that you are doing all steps from a Unix machine (I’ve done them from Fedora Linux but it should work on any Linux, BSD or OS X with potential adaptation). It is possible to do it on Windows I suppose, but I don’t have Windows and can’t explain.

The steps are:

  • Flash the Raspbian image to a SD card;
  • Sync everything and mount the second partition created;
  • Modify files on the SD card to allow SSH (and optionally configure WiFi);
  • Put the SD card in your RPi and plug the power;
  • Wait a couple of minute for thing to settle;
  • Either check your DHCP server (e.g. your router) for the RPi IP address, or scan your network);
  • Connect to your RPi using SSH and finish the setup;
  • (option) Upgrade to Debian Jessie (you will have to view the full article)!

Flash the Raspbian image to a SD card

Raspbian LogoThere are already numerous guides online on how to do that. So I will be brief, but refer to those guides for your exact configuration. I assume a new SD card which has already a Windows FAT partition with a size bigger than 4GB (I recommend 16GB). When I plugged that SD card on my laptop it was recognised as /dev/mmcblk0p1 and automatically mounted. First we need to unmount this partition and then to remember the device name (without the partition suffix, so /dev/mmcblk0 in my case). Note that if you are on BSD or OS X those steps are slightly different, check online. Using the device name we can flash the Raspbian image (after downloading the zip file, check that the SHA-1 checksum match).

$ sudo umount /dev/mmcblk0p1
$ unzip -c 2015-05-05-raspbian-wheezy.img.zip | sudo dd bs=1M of=/dev/mmcblk0
$ sudo sync; sleep 4; sudo sync

After doing the above you should have now 2 new partitions on your SD card. The first partition (suffix p1) is the boot one and is formatted as FAT (was <60MB for me). The second one (suffixed p2) is the root partition and is formatted as ext4 (roughly 3GB). That’s the partition /dev/mmcblk0p2 which is interested for the next step.

Allow SSH access

OpenSSH LogoYou need to mount the second partition now, So create first a mount point and then mount the partition to it.

$ sudo mkdir /mnt/rpi
$ sudo mount /dev/mmcblk0p2 /mnt/rpi
$ cd /mnt/rpi/etc
$ sudo mv rc2.d/K01ssh rc2.d/S01ssh
$ sudo mv rc3.d/K01ssh rc3.d/S01ssh
$ sudo mv rc4.d/K01ssh rc4.d/S01ssh
$ sudo mv rc5.d/K01ssh rc5.d/S01ssh

That’s it!

Network Wireless by OxygenOptional: if you do not have an Ethernet interface and need to use WiFi, you need to add the WiFi configuration (your SSID – or WiFi network name – and your WiFi password). Assuming you have something like WPA2-PSK, you simply need to edit the file /mnt/rpi/etc/wpa_supplicant/wpa_supplicant.conf and add the following at the end of the file:

network={
    ssid="Your_WiFi_SSID"
    psk="Your_WiFi_password"
}

The network configuration on Raspbian is set to use DHCP, so after booting the system will use whatever network interface it has available and make DHCP requests in order to get an IP address.

Note: please don’t use both the Ethernet and WiFi interfaces if you they are both on the same network. Such a configuration is possible, but it won’t work out-of-the-box. So set up first one interface, make it work and then add the other one (look for online resources about how to configure Linux for 2 NIC on the same subnets).

Now sync all changes to the SD card:

$ cd ~ ; sudo umount /mnt/rpi

Start Raspbian and connect to it

Before removing the SD card from your computer, be sure that you properly unmounted it (check last steps of previous chapter).

Now remove the SD card from the computer, insert it in the Raspberry Pi, plug the Ethernet cable (or the WiFi USB dongle) and then the USB power plug. The LEDs of your RPi should light up (PWR – red one – means that your power supply is good enough; ACT – green one – should not be steady green, it means your SD card is not readable or was wrongly flashed, it should blink). After the RPi has completed boot up, the ACT LED should be off (mostly), meaning that there are no more I/O activities going on. That’s when you can be sure that the RPi has sent its DHCP probes and should have an IP address assigned.

To know your Raspberry Pi IP address, you can either go to your DHCP server (e.g. your router) and check which addess was assigned to it, or simply scan your network. To scan your network you need to know your subnet (e.g. 192.168.1.0 with a netmask of 255.255.255.0) and have nmap installed on your computer (sudo dnf install nmap will work for Fedora, and it is as easy for Debian/Ubuntu-based distros as well, just replace dnf by apt-get).

$ sudo nmap -sP 192.168.1.0/24

Of course you need to adapt the above command to your subnet. The “/24” part is the netmask equivalent of 255.255.255.0. I recommend running the above command with sudo because it will display the MAC address of all the discovered devices which will help you spot your Raspberry Pi as nmap is displaying the vendor attached to each MAC address. See for yourself in the example output:

Starting Nmap 6.47 ( http://nmap.org ) at 2015-07-19 20:12 CEST
(...)
Nmap scan report for raspberrypi.lan (192.168.1.9)
Host is up (0.0060s latency).
MAC Address: B8:27:EB:1E:42:18 (Raspberry Pi Foundation)
(...)
Nmap done: 256 IP addresses (8 hosts up) scanned in 2.05 seconds

Now you can simply connect to your RPi by using the user pi and password raspberrypi (which are default on Raspbian):

$ ssh pi@192.168.1.9
The authenticity of host 'raspberrypi (192.168.1.9)' can't be established.
ECDSA key fingerprint is SHA256:WSF9Rpmh0Mr/JYUye8r69nXzwZtYbdH0xJ5M4AFYxYY.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'raspberrypi,192.168.1.9' (ECDSA) to the list of known hosts.
pi@raspberrypi's password: 
Linux raspberrypi 3.18.11-v7+ #781 SMP PREEMPT Tue Apr 21 18:07:59 BST 2015 armv7l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

NOTICE: the software on this Raspberry Pi has not been fully configured. Please run 'sudo raspi-config'

pi@raspberrypi ~ $

As it is advised, you can run the command sudo raspi-config especially to increase the partition size so it uses the complete SD card space available.

That’s it, you have installed Raspbian on a Raspberry Pi without a screen or keyboard (headless). I strongly recommend to follow my advice about Raspberry Pi Raspbian post-installation and security.

Picture credits: The Debian Logo belongs to the Debian project. Raspberry Pi and its logo are trademarks of the Raspberry Pi Foundation. The OpenSSH logo is copyrighted by OpenBSD. The wireless device is an icon from the Oxygen set of the KDE project provided under GNU LGPLv3.

 

Update: I forgot the icing on the cake: upgrading to Debian Jessie. Continue reading to learn a quick way to do it.

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