How to setup Raspberry Pi Zero without mouse and keyboard attached to micro USB

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Published on June 16th 2021 - Listed in Hardware Linux Network


For a new project I bought a Raspberry Pi Zero WH (W = Wireless, H = Headers) together with a ReSpeaker multi-microphone.

Raspberry Pi Zero WH with ReSpeaker

This was the first time I ever had a Pi Zero in the hands. I've had a Raspberry Pi 2 and 3b+ before and kind of got used to the onboard USB ports. Even though this is clearly documented, I only realized now that I don't have any USB-to-microUSB adapters - therefore no way to attach a mouse or keyboard to the Pi Zero.

Verifying boot

After I installed Raspberry Pi OS (Raspbian) on the microSD card (using the Raspberry Pi Imager) I verified that the Pi Zero actually boots. I had a HDMI-to-miniHDMI adapter available (see photo above) so I was able to verify the boot on the screen.

Yep, the Pi Zero correctly booted correctly. But how would I be able to log in to the Pi, configure WLAN and install the needed software without a keyboard?

The magical boot partition

To solve this, the Pi Zero (or basically any Raspberry Pi) can be told to automatically:

  • connect to a certain WLAN
  • start openssh-server (SSH server)

at boot time.

The trick is to manually place the relevant files into the Pi's boot partition.

Note: The microSD card is formatted in a way that two partitions exist. Partition 1 is the boot partition; it holds the Kernel, drivers and other information needed to boot the system. Partition 2 contains all other data, including the Operating System and user data (/home/pi).

To do that, I turned off the power of the Pi Zero, removed the microSD card and connected it to my computer (using a microSD-to-SD adapter and then using a card reader):

In my own OS (Linux Mint) I could see that the card reader was detected and the SD card seen as sdf:

ck@mintp ~ $ dmesg
[...]
[698910.390989] usb 1-7.1: new high-speed USB device number 5 using xhci_hcd
[698910.979313] usb 1-7.1: New USB device found, idVendor=0bda, idProduct=0151, bcdDevice=51.95
[698910.979315] usb 1-7.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[698910.979318] usb 1-7.1: Product: USB2.0-CRW
[698910.979319] usb 1-7.1: Manufacturer: Generic
[698910.979321] usb 1-7.1: SerialNumber: 20060413092100000
[698910.999520] usb-storage 1-7.1:1.0: USB Mass Storage device detected
[698910.999629] scsi host6: usb-storage 1-7.1:1.0
[698912.039413] scsi 6:0:0:0: Direct-Access     Generic- Compact Flash    1.00 PQ: 0 ANSI: 0 CCS
[698912.045563] scsi 6:0:0:1: Direct-Access     Generic- SM/xD-Picture    1.00 PQ: 0 ANSI: 0 CCS
[698912.051680] scsi 6:0:0:2: Direct-Access     Generic- SD/MMC           1.00 PQ: 0 ANSI: 0 CCS
[698912.057815] scsi 6:0:0:3: Direct-Access     Generic- MS/MS-Pro        1.00 PQ: 0 ANSI: 0 CCS
[698912.058090] sd 6:0:0:0: Attached scsi generic sg3 type 0
[698912.058273] sd 6:0:0:1: Attached scsi generic sg4 type 0
[698912.058467] sd 6:0:0:2: Attached scsi generic sg5 type 0
[698912.058614] sd 6:0:0:3: Attached scsi generic sg6 type 0
[698912.152729] usb 1-7.1: reset high-speed USB device number 5 using xhci_hcd
[698912.392881] usb 1-7.1: reset high-speed USB device number 5 using xhci_hcd
[698912.636537] usb 1-7.1: reset high-speed USB device number 5 using xhci_hcd
[698912.880849] usb 1-7.1: reset high-speed USB device number 5 using xhci_hcd
[698913.124734] usb 1-7.1: reset high-speed USB device number 5 using xhci_hcd
[698913.368804] usb 1-7.1: reset high-speed USB device number 5 using xhci_hcd
[698913.501135] sd 6:0:0:1: [sde] 0 512-byte logical blocks: (0 B/0 B)
[698913.501138] sd 6:0:0:1: [sde] 0-byte physical blocks
[698914.170576] sd 6:0:0:2: [sdf] 30367744 512-byte logical blocks: (15.5 GB/14.5 GiB)
[698914.170891] sd 6:0:0:1: [sde] Test WP failed, assume Write Enabled
[698914.171208] sd 6:0:0:1: [sde] Asking for cache data failed
[698914.171212] sd 6:0:0:1: [sde] Assuming drive cache: write through
[698914.171508] sd 6:0:0:0: [sdd] Attached SCSI removable disk
[698914.173131] sd 6:0:0:2: [sdf] Write Protect is off
[698914.173134] sd 6:0:0:2: [sdf] Mode Sense: 03 00 00 00
[698914.175126] sd 6:0:0:2: [sdf] No Caching mode page found
[698914.175129] sd 6:0:0:2: [sdf] Assuming drive cache: write through
[698914.187861] sd 6:0:0:3: [sdg] Attached SCSI removable disk
[698914.188411] sd 6:0:0:1: [sde] Attached SCSI removable disk
[698914.212110]  sdf: sdf1 sdf2
[698914.216123] sd 6:0:0:2: [sdf] Attached SCSI removable disk

The two partitions can be seen easily using fdisk:

ck@mintp ~ $ sudo fdisk -l /dev/sdf
[sudo] password for ck:       
Disk /dev/sdf: 14.49 GiB, 15548284928 bytes, 30367744 sectors
Disk model: SD/MMC          
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x1443eb9a

Device     Boot  Start      End  Sectors  Size Id Type
/dev/sdf1         8192   532479   524288  256M  c W95 FAT32 (LBA)
/dev/sdf2       532480 30367743 29835264 14.2G 83 Linux

The mentioned boot partition is the first partition and is formatted as FAT32. FAT32 is a "global" file system format which is accepted by the major Operating Systems (Windows, macOS and Linux - even BSD, too) and should not cause a problem to mount the partition and take a look into the filesystem:

ck@mintp ~ $ sudo mount /dev/sdf1 /mnt
ck@mintp ~ $ ll /mnt
total 48178
drwxr-xr-x  3 root root    3584 Jan  1  1970 ./
drwxr-xr-x 25 root root    4096 Mar 11 13:06 ../
-rwxr-xr-x  1 root root   25607 Mar  3 14:40 bcm2708-rpi-b.dtb*
-rwxr-xr-x  1 root root   25870 Mar  3 14:40 bcm2708-rpi-b-plus.dtb*
-rwxr-xr-x  1 root root   25218 Mar  3 14:40 bcm2708-rpi-b-rev1.dtb*
-rwxr-xr-x  1 root root   25529 Mar  3 14:40 bcm2708-rpi-cm.dtb*
-rwxr-xr-x  1 root root   25352 Mar  3 14:40 bcm2708-rpi-zero.dtb*
-rwxr-xr-x  1 root root   26545 Mar  3 14:40 bcm2708-rpi-zero-w.dtb*
-rwxr-xr-x  1 root root   26745 Mar  3 14:40 bcm2709-rpi-2-b.dtb*
-rwxr-xr-x  1 root root   26894 Mar  3 14:40 bcm2710-rpi-2-b.dtb*
-rwxr-xr-x  1 root root   28392 Mar  3 14:40 bcm2710-rpi-3-b.dtb*
-rwxr-xr-x  1 root root   29011 Mar  3 14:40 bcm2710-rpi-3-b-plus.dtb*
-rwxr-xr-x  1 root root   26890 Mar  3 14:40 bcm2710-rpi-cm3.dtb*
-rwxr-xr-x  1 root root   48810 Apr 30 16:01 bcm2711-rpi-400.dtb*
-rwxr-xr-x  1 root root   49090 Mar  3 14:40 bcm2711-rpi-4-b.dtb*
-rwxr-xr-x  1 root root   49202 Mar  3 14:40 bcm2711-rpi-cm4.dtb*
-rwxr-xr-x  1 root root   52456 Jan  5 08:30 bootcode.bin*
-rwxr-xr-x  1 root root     166 Jan  1  1980 cmdline.txt*
-rwxr-xr-x  1 root root    1784 May  7 16:43 config.txt*
-rwxr-xr-x  1 root root   18693 Jan  5 08:30 COPYING.linux*
-rwxr-xr-x  1 root root    3191 Apr 30 16:01 fixup4cd.dat*
-rwxr-xr-x  1 root root    5446 Apr 30 16:01 fixup4.dat*
-rwxr-xr-x  1 root root    8454 Apr 30 16:01 fixup4db.dat*
-rwxr-xr-x  1 root root    8452 Apr 30 16:01 fixup4x.dat*
-rwxr-xr-x  1 root root    3191 Apr 30 16:01 fixup_cd.dat*
-rwxr-xr-x  1 root root    7314 Apr 30 16:01 fixup.dat*
-rwxr-xr-x  1 root root   10298 Apr 30 16:01 fixup_db.dat*
-rwxr-xr-x  1 root root   10298 Apr 30 16:01 fixup_x.dat*
-rwxr-xr-x  1 root root     145 May  7 17:07 issue.txt*
-rwxr-xr-x  1 root root 6320888 Apr 30 16:01 kernel7.img*
-rwxr-xr-x  1 root root 6694528 Apr 30 16:01 kernel7l.img*
-rwxr-xr-x  1 root root 7758283 Apr 30 16:01 kernel8.img*
-rwxr-xr-x  1 root root 5981944 Apr 30 16:01 kernel.img*
-rwxr-xr-x  1 root root    1594 Jan  5 08:30 LICENCE.broadcom*
drwxr-xr-x  2 root root   18432 May  7 16:42 overlays/
-rwxr-xr-x  1 root root  793084 Apr 30 16:01 start4cd.elf*
-rwxr-xr-x  1 root root 3722504 Apr 30 16:01 start4db.elf*
-rwxr-xr-x  1 root root 2228768 Apr 30 16:01 start4.elf*
-rwxr-xr-x  1 root root 2981160 Apr 30 16:01 start4x.elf*
-rwxr-xr-x  1 root root  793084 Apr 30 16:01 start_cd.elf*
-rwxr-xr-x  1 root root 4794472 Apr 30 16:01 start_db.elf*
-rwxr-xr-x  1 root root 2952928 Apr 30 16:01 start.elf*
-rwxr-xr-x  1 root root 3704712 Apr 30 16:01 start_x.elf*

And now we can create the mentioned files.

  • To enable SSH at start, simply create an empty file called "ssh" in the boot partition
  • To automatically connect to a specific WLAN, create a file called wpa_supplicant.conf in the boot partition. This file needs to contain the WLAN information, including the WPA2 passphrase.

The first one is easy:

ck@mintp ~ $ sudo touch /mnt/ssh
ck@mintp ~ $ ls -la /mnt/ssh
-rwxr-xr-x 1 root root 0 Jun 15 11:19 /mnt/ssh

The second file, wpa_supplicant.conf needs to contain your WLAN information. I created the file using vi(m), but you can also use a text editor and then save or copy the file into the mounted boot partition:

ck@mintp ~ $ sudo vi /mnt/wpa_supplicant.conf
ck@mintp ~ $ cat /mnt/wpa_supplicant.conf
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=CH
network={
    ssid="My-WLAN"
    psk="passphrase"
}

Make sure you set country, ssid and psk to your own environment! The country is using a two letter country code using ISO 3166-1 standard.

Now unmount the microSD card's boot partition:

ck@mintp ~ $ sudo umount /mnt

Then eject/unplug the card from your computer and insert it back into the Raspberry Pi Zero.

Power on the Raspberry Pi Zero and it starts booting.

Success! WLAN connected and SSH available!

Now that the Raspberry Pi Zero has booted up again, this time it automatically connected to the WLAN and received an IP address from the DHCP server. This IP address is shown in the "Welcome to Raspberry Pi" window:

Raspberry Pi automatically connected to WLAN at boot

Testing SSH from my computer:

ck@mintp ~ $ ssh pi@192.168.15.15
The authenticity of host '192.168.15.15 (192.168.15.15)' can't be established.
ECDSA key fingerprint is SHA256:Wg1IpcF3NZyWOgVMP40QSGox8DxTHTGZI5IYit/z4Lg.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '192.168.15.15' (ECDSA) to the list of known hosts.
pi@192.168.15.15's password:
Linux raspberrypi 5.10.17+ #1414 Fri Apr 30 13:16:27 BST 2021 armv6l

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.
Last login: Fri May  7 16:17:53 2021

SSH is enabled and the default password for the 'pi' user has not been changed.
This is a security risk - please login as the 'pi' user and type 'passwd' to set a new password.

pi@raspberrypi:~ $ 

Note: Default password of the "pi" user is "raspberry"

Hurray! I'm in the OS of the Raspberry Pi Zero and can now continue with configuration and software installation - without any keyboard or mouse attached for initial configuration.

There's a great video, too

In case you prefer to watch a video of all this, there's a great and helpful video from Crazy Will Tech Show on YouTube.


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