Raspberry Pi: Difference between revisions

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* Plan to install packages which consume more space than can be loaded into RAM
* Plan to install packages which consume more space than can be loaded into RAM
* Plan to install kernel modules (such as ZFS)
* Plan to install kernel modules (such as ZFS)
== Compability list ==
As of Alpine 3.19:
* '''armhf''' (defconfig bcmrpi) - Raspberry Pi 1, Zero, ZeroW, cm1
* '''armv7''' (defconfig bcm2709) - Raspberry Pi 2, 3, 3+, Zero2W, cm3, cm3+
* '''aarch64''' (defconfig bcm2711) - Raspberry Pi 3, 3+, 4, 400, Zero2W, cm3, cm3+, cm4, 5


== Preparation ==
== Preparation ==


# [https://alpinelinux.org/downloads/ Download] the Alpine for Raspberry Pi tarball. You should be safe using the '''armhf''' build on all versions of Raspberry Pi (including Pi Zero and Compute Modules); but it may perform less optimally on recent versions of Raspberry Pi. The '''armv7''' build is compatible with Raspberry Pi 2 Model B. The '''aarch64''' build should be compatible with Raspberry Pi 2 Model v1.2, Raspberry Pi 3 and Compute Module 3, and Raspberry Pi 4 model B.
# [https://alpinelinux.org/downloads/ Download] the Alpine for Raspberry Pi tarball. Use the compability list above when choosing image/file to download.  
# [[Create_a_Bootable_Device#Manually_copying_Alpine_files|Create a bootable FAT32 partition on your SD card.]] The partitioning and formatting part of the instructions on the linked page could be done using a graphical partitioning tool such as [https://en.wikipedia.org/wiki/GNOME_Disks gnome-disks], just make sure the partition type is <code>W95 FAT32 (LBA)</code>. (The current type can be found in the "Type" column in the output of <code>fdisk -l</code>.)
# [[Create_a_Bootable_Device#Manually_copying_Alpine_files|Create a bootable FAT32 partition on your SD card.]] The partitioning and formatting part of the instructions on the linked page could be done using a graphical partitioning tool such as [https://en.wikipedia.org/wiki/GNOME_Disks gnome-disks], just make sure the partition type is <code>W95 FAT32 (LBA)</code>. (The current type can be found in the "Type" column in the output of <code>fdisk -l</code>.)
# Extract the tarball to the root of the bootable FAT32 partition.
# Extract the tarball to the root of the bootable FAT32 partition.
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To setup a headless system, a bootstrapping configuration overlay file [https://github.com/macmpi/alpine-linux-headless-bootstrap  headless.apkovl.tar.gz] may be added to enable basic networking, so that following configuration steps can be performed under <code>ssh</code>. Pi Zero may be configured with simple USB ethernet-gadget networking with another computer sharing its internet connection.
To setup a headless system, a bootstrapping configuration overlay file [https://github.com/macmpi/alpine-linux-headless-bootstrap  headless.apkovl.tar.gz] may be added to enable basic networking, so that following configuration steps can be performed under <code>ssh</code>. Pi Zero may be configured with simple USB ethernet-gadget networking with another computer sharing its internet connection.


Optionally create a '''usercfg.txt''' file on the partition to configure low-level system settings. Specifications can be found [https://www.raspberrypi.org/documentation/configuration/config-txt here]. However, note some settings can only be set directly in '''config.txt''', which may be overwritten after updates. In particular, <code>gpu_mem</code> will have no effect when specified in '''usercfg.txt''' ([https://github.com/raspberrypi/firmware/issues/1332 source]). Some interesting values include:
It is recommended to create a '''usercfg.txt''' file on boot partition to configure low-level system settings, as '''config.txt''' may be replaced during bootloader/system upgrades: details can be found [https://www.raspberrypi.com/documentation/computers/config_txt.html here].<br>
However, note some [https://www.raspberrypi.com/documentation/computers/config_txt.html#include settings] can only be set in '''config.txt''', and will have no effect when specified in '''usercfg.txt''' (e.g. <code>gpu_mem</code>). Some interesting values include:
* To enable the UART console: <code>enable_uart=1</code>
* To enable the UART console: <code>enable_uart=1</code>
* To enable audio: <code>dtparam=audio=on</code>
* To enable audio: <code>dtparam=audio=on</code>
* If you see black edges around your screen after booting the Pi, you can add <code>disable_overscan=1</code>
* By default system will use legacy video driver: some [https://www.raspberrypi.com/documentation/computers/legacy_config_txt.html#legacy-video-options options] may be used to adjust displays modes (e.g. if you see black edges around your screen after booting the Pi, you can add <code>disable_overscan=1</code>). Alternatively Linux DRM-KMS driver may be used (see below).
* If you plan to install on a Pi Compute Module 4 with I/O board, you may need to add: <code>otg_mode=1</code>
* If you plan to install on a Pi Compute Module 4 with I/O board, you may need to add: <code>otg_mode=1</code>


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# Insert the SD card into the Raspberry Pi and power it on
# Insert the SD card into the Raspberry Pi and power it on
# Login into the Alpine system as root.  Leave the password empty.
# Login into the Alpine system as root.  Leave the password empty.
# Check the current date and time by issuing <code>date</code>. Correct if necessary by issuing <code>date -s YYYYMMDDhhmm</code>.
# Type <code>setup-alpine</code>
# Type <code>setup-alpine</code>
# Once the installation is complete, commit the changes by typing <code>lbu commit -d</code>
# Once the installation is complete, commit the changes by typing <code>lbu commit -d</code>
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Note: this does not upgrade the kernel. In order to upgrade the kernel, a full upgrade of the Alpine Linux version must be performed as described in [[Upgrading Alpine#Upgrading Alpine Linux on other removable media (such as CF/USB)|upgrading Alpine Linux for removable media]].
Note: this does not upgrade the kernel. In order to upgrade the kernel, a full upgrade of the Alpine Linux version must be performed as described in [[Upgrading Alpine#Upgrading Alpine Linux on other removable media (such as CF/USB)|upgrading Alpine Linux for removable media]].


=== Clock-related error messages ===
=== Linux Kernel Graphics Modes ===
By default system configuration will use legacy video driver: this driver has some limitations and is lacking support.<br>
It is recommended to enable Linux DRM-KMS driver by adding the following to '''usercfg.txt''':
# Enable DRM VC4 V3D driver
dtoverlay=vc4-kms-v3d
max_framebuffers=2
# Don't have the firmware create an initial video= setting in cmdline.txt.
# Use the kernel's default instead.
disable_fw_kms_setup=1
Note: This overlay disables legacy video [https://www.raspberrypi.com/documentation/computers/legacy_config_txt.html#legacy-video-options options].
 
Install the Mesa drivers (Pi4 and Pi5):
 
{{cmd|apk add {{pkg|mesa-dri-gallium|arch=a*}}}}
 
Then reboot:
 
{{cmd|lbu_commit -d; reboot}}
 
=== Wireless drivers ===
As of Alpine 3.17, Wifi and Bluetooth drivers are available within install image: they are part of <code>linux-firmware-brcm</code> (and linked dependencies).<br>
Since kernel 6.1.25 (i.e. Alpine 3.18), onboard bluetooth is enabled & autoprobed by default (it may be disabled by setting [https://github.com/raspberrypi/rpi-firmware/tree/master/overlays krnbt] off).


During the booting time, you might notice errors related to the hardware clock.  The Raspberry Pi does not have
== Troubleshooting ==
a hardware clock, thus you need to disable the hwclock daemon and enable swclock:
<code>raspinfo</code> utility can be used as a first step to diagnose issues: it will make a log report of essential Pi system configuration, and is often used as a reference to submit questions or bug reports within Raspberry Pi community (Forums, Github, etc).<br>
It can be installed with <code>raspberrypi-utils-raspinfo</code> subpackage.


{{cmd|rc-update add swclock boot   # enable the software clock
=== Long boot time when running headless ===
rc-update del hwclock boot    # disable the hardware clock}}


Since the Raspberry Pi does not have a clock, Alpine Linux needs to know what the time is by using a
If no peripherals are connected, the system might hang for an exceptionally long period of time while it attempts to accumulate entropy.
[https://en.wikipedia.org/wiki/Network_Time_Protocol Network Time Protocol (NTP)] daemon.  Make sure you have a
NTP daemon installed and running. If you are not sure, you can install an NTP client by running the following
command:


{{cmd|setup-ntp}}
If this is the case, simply plugging in any USB device should work around this issue, since it increases the amount of entropy available to the kernel via interrupts.


The Busybox NTP client might be the most lightweight solution.  Save the changes and reboot, once the NTP software is
=== apk indicating 'No space left on device' ===
installed and running:


{{cmd|lbu commit -d
Note some models of the Raspberry Pi such as the 3A+ only have 512M of RAM, which on fresh Alpine deployment will only leave around 200M for tmpfs root. It's important to keep this limitation in mind when using these boards.
reboot}}


After reboot, make sure the <code>date</code> command outputs the correct date and time.
=== Clock-related error messages ===


=== WiFi on boot ===
During the booting time, you might notice errors related to the hardware clock.  Many Raspberry Pi do not have a hardware clock, or may have one without battery, in which case the behaviour depends on whether you physically cut power or not.  
If you have already [[Connecting_to_a_wireless_access_point|configured WiFi]] during the setup, the connection will not return on reboot.
You will need to start up a service to automatically connect to the wireless access point.
# Run <code>rc-update add wpa_supplicant boot</code> to connect to the wireless access point during bootup.
# Run it manually with <code>rc-service wpa_supplicant start</code>.


=== Enable Graphics ===
Also, <code>setup-alpine</code> will adapt the installation to the type of Raspberry Pi you use, which means for example that on a RPI5, you will see <code>hwclock></code> service, whereas on a RPI4 it will use <code>swclock</code>. In doubt, make sure to do the installation on the target hardware.
Remount the boot partition writeable (i.e. <code>/media/mmcblk0p1</code>):


{{cmd|mount /media/mmcblk0p1 -o rw,remount}}
If you still experience clock errors, add the following line to '''/etc/chrony/chrony.conf''':


Add the following lines to <code>/media/mmcblk0p1/config.txt</code>:
<code>makestep 0.1 3</code>  


dtoverlay=vc4-kms-v3d
== Persistent storage ==
=== Traditional disk-based (sys) installation ===
{{Merge|Classic install or sys mode on Raspberry Pi|There's an existing page for sys-installations on RasPi.}}


If you are experiencing graphical issues, you can also try:
It is also possible to switch to a fully disk-based installation. This is not yet formally supported, but can be done somewhat manually. This frees all the memory otherwise needed for the root filesystem, allowing more installed packages.


dtoverlay=vc4-fkms-v3d
Split your SD card into two partitions: the FAT32 boot partition described above (in this example it'll be <code>mmcblk0p1</code>) , and a second partition to hold the root filesystem (here it'll be <code>mmcblk0p2</code>). Boot and configure your diskless system as above, then create a root filesystem:


And perhaps also raising the default <code>gpu_mem</code>:
{{cmd|apk add {{pkg|e2fsprogs|arch=a*}}
mkfs.ext4 /dev/mmcblk0p2}}


gpu_mem=128
Now do a disk install via a mountpoint. The <code>setup-disk</code> script will give some errors about syslinux/extlinux, but you can ignore them.
The Raspberry Pi doesn't need them to boot.


Note that raising the gpu memory is not likely to [https://www.raspberrypi.com/documentation/computers/config_txt.html#gpu_mem actually improve performance on the Pi4]
{{cmd|<nowiki>mkdir /stage
mount /dev/mmcblk0p2 /stage
setup-disk -o /media/mmcblk0p1/MYHOSTNAME.apkovl.tar.gz /stage
# (ignore errors about syslinux/extlinux)</nowiki>}}


Install the Mesa drivers:
Add a line to <code>/stage/etc/fstab</code> to mount the Pi's boot partition again:


{{cmd|<nowiki>apk add mesa-dri-gallium</nowiki>}}
{{cmd|/dev/mmcblk0p1 /media/mmcblk0p1 vfat defaults 0 0}}


Then reboot:
Now add a <code>root=/dev/mmcblk0p2</code> parameter to the Pi's boot command line, either <code>cmdline-rpi2.txt</code> or <code>cmdline-rpi.txt</code> depending on model:


{{cmd|lbu_commit -d; reboot}}
{{cmd|<nowiki>mount -o remount,rw /media/mmcblk0p1
sed -i '$ s/$/ root=\/dev\/mmcblk0p2/' /media/mmcblk0p1/cmdline-rpi2.txt</nowiki>}}


=== WiFi drivers ===
You might also consider <code>overlaytmpfs=yes</code> here, which will cause the underlying SD card root filesystem to be mounted read-only, with an overlayed tmpfs for modifications which will be discarded at shutdown.
As of Alpine 3.14, the WiFi drivers for the Raspberry Pi were moved from <code>linux-firmware-brcm</code> to the <code>linux-firmware-cypress</code> package (source?). Since the images seem to be an outdated version of the former, Wi-Fi will work during installation, but after the first update it will break.
Use the ethernet interface to download the required packages:


{{cmd|apk add linux-firmware-cypress}}
N.B. <b>the contents of /boot will be ignored when the Pi boots</b>. It will use the kernel, initramfs, and modloop images from the FAT32 boot partition. To update the kernel, initfs or modules, you will need to manually (generate and) copy these to the boot partition or you could use bind mount, in which case,
copying the files to boot partition manually, is not needed.


And reboot.
{{cmd|<nowiki>echo /media/mmcblk0p1/boot /boot none defaults,bind 0 0 >> /etc/fstab</nowiki>}}


== Persistent storage ==
=== Loopback image with overlayfs ===
=== Loopback image with overlayfs ===


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If it is something a bit bigger, then you can use <code>apk add</code> but then not commit it. It will be persistent (in <code>/user</code>), but be sure to check everything you need is in that directory and not in folders you have not made persistent.
If it is something a bit bigger, then you can use <code>apk add</code> but then not commit it. It will be persistent (in <code>/user</code>), but be sure to check everything you need is in that directory and not in folders you have not made persistent.
=== Traditional disk-based (sys) installation ===
{{Merge|Classic install or sys mode on Raspberry Pi|There's an existing page for sys-installations on RasPi.}}
It is also possible to switch to a fully disk-based installation. This is not yet formally supported, but can be done somewhat manually. This frees all the memory otherwise needed for the root filesystem, allowing more installed packages.
Split your SD card into two partitions: the FAT32 boot partition described above (in this example it'll be <code>mmcblk0p1</code>) , and a second partition to hold the root filesystem (here it'll be <code>mmcblk0p2</code>). Boot and configure your diskless system as above, then create a root filesystem:
{{cmd|apk add e2fsprogs
mkfs.ext4 /dev/mmcblk0p2}}
Now do a disk install via a mountpoint. The <code>setup-disk</code> script will give some errors about syslinux/extlinux, but you can ignore them.
The Raspberry Pi doesn't need them to boot.
{{cmd|<nowiki>mkdir /stage
mount /dev/mmcblk0p2 /stage
setup-disk -o /media/mmcblk0p1/MYHOSTNAME.apkovl.tar.gz /stage
# (ignore errors about syslinux/extlinux)</nowiki>}}
Add a line to <code>/stage/etc/fstab</code> to mount the Pi's boot partition again:
{{cmd|/dev/mmcblk0p1 /media/mmcblk0p1 vfat defaults 0 0}}
Now add a <code>root=/dev/mmcblk0p2</code> parameter to the Pi's boot command line, either <code>cmdline-rpi2.txt</code> or <code>cmdline-rpi.txt</code> depending on model:
{{cmd|<nowiki>mount -o remount,rw /media/mmcblk0p1
sed -i '$ s/$/ root=\/dev\/mmcblk0p2/' /media/mmcblk0p1/cmdline-rpi2.txt</nowiki>}}
You might also consider <code>overlaytmpfs=yes</code> here, which will cause the underlying SD card root filesystem to be mounted read-only, with an overlayed tmpfs for modifications which will be discarded at shutdown.
N.B. <b>the contents of /boot will be ignored when the Pi boots</b>. It will use the kernel, initramfs, and modloop images from the FAT32 boot partition. To update the kernel, initfs or modules, you will need to manually (generate and) copy these to the boot partition or you could use bind mount, in which case,
copying the files to boot partition manually, is not needed.
{{cmd|<nowiki>echo /media/mmcblk0p1/boot /boot none defaults,bind 0 0 >> /etc/fstab</nowiki>}}
=== Persistent Installation on Raspberry Pi 3 ===
See [[Classic install or sys mode on Raspberry Pi]] and https://web.archive.org/web/20171125115835/https://forum.alpinelinux.org/comment/1084#comment-1084
=== Persistent Installation on Raspberry Pi 4 ===
As of 3.14, setup-alpine should ask you if you want to create a sys mode partition on your Raspberry Pi 4.


== Netboot ==
== Netboot ==
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With the above configured the Raspberry Pi 4 should be able to boot from the network without an SD card.
With the above configured the Raspberry Pi 4 should be able to boot from the network without an SD card.


== Troubleshooting ==
=== Wireless support with older Alpine images ===


=== Long boot time when running headless ===
In Alpine 3.14, the WiFi drivers for the Raspberry Pi were moved from <code>linux-firmware-brcm</code> to the <code>linux-firmware-cypress</code> package (source?). Since the images seem to be an outdated version of the former, Wi-Fi will work during installation, but after the first update it will break.
Use the ethernet interface to download the required packages:


If no peripherals are connected, the system might hang for an exceptionally long period of time while it attempts to accumulate entropy.
{{cmd|apk add {{pkg|linux-firmware-cypress|arch=a*}}}}


If this is the case, simply plugging in any USB device should work around this issue, since it increases the amount of entropy available to the kernel via interrupts.
And reboot.
 
=== apk indicating 'No space left on device' ===
 
Note some models of the Raspberry Pi such as the 3A+ only have 512M of RAM, which on fresh Alpine deployment will only leave around 200M for tmpfs root. It's important to keep this limitation in mind when using these boards.
 
=== Wireless support with older Alpine images ===


If you need Wi-Fi, you'll need to [https://github.com/RPi-Distro/firmware-nonfree/tree/master/brcm download] the latest Broadcom drivers to your SD card.
If you need Wi-Fi, you'll need to [https://github.com/RPi-Distro/firmware-nonfree/tree/master/brcm download] the latest Broadcom drivers to your SD card.
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   git clone --depth 1 https://github.com/RPi-Distro/firmware-nonfree.git
   git clone --depth 1 https://github.com/RPi-Distro/firmware-nonfree.git
   cp firmware-nonfree/brcm/* /mnt/sdcard/firmware/brcm
   cp firmware-nonfree/brcm/* /mnt/sdcard/firmware/brcm
== Enable the Serial Console ==
Besides having <code>enable_uart=1</code> in ''usercfg.txt'', the kernel command-line option <var>console</var> needs to be changed to <code>console=serial0,115200</code> in ''cmdline.txt''.
From a Linux desktop, connect to it with something like this:
{{cmd|cu -l /dev/ttyUSB0 -s 115200}}


== See Also ==
== See Also ==

Latest revision as of 16:02, 31 October 2024

Warning: 11 Feb 2021 - There is currently a known bug upstream
kernel/initramfs cannot be loaded from subdirectory with same name as volume label. Since the kernel is installed to boot/, you must not use a label named boot for the fat32 partition.


This tutorial explains how to install Alpine Linux on a Raspberry Pi. Alpine Linux will be installed in diskless mode, hence, Alpine Local Backup (lbu) is required to save modifications between reboots.

For scenarios where there is not expected to be significant changes to disk after setup (like running a static HTTP server), this is likely preferable, as running the entire system from memory will improve performance (by avoiding the slow SD card) and improve the SD card life (by reducing the writes to the card, as all logging will happen in RAM). Diskless installations still allow you to install packages, save local files, and tune the system to your needs.

If any of the following apply, then installation in sys-mode installation is likely more appropriate.

  • There will be constant changes to the disk after initial setup (for example, if you expect people to login and save files to their home directories)
  • Logs should persists across reboots
  • Plan to install packages which consume more space than can be loaded into RAM
  • Plan to install kernel modules (such as ZFS)

Compability list

As of Alpine 3.19:

  • armhf (defconfig bcmrpi) - Raspberry Pi 1, Zero, ZeroW, cm1
  • armv7 (defconfig bcm2709) - Raspberry Pi 2, 3, 3+, Zero2W, cm3, cm3+
  • aarch64 (defconfig bcm2711) - Raspberry Pi 3, 3+, 4, 400, Zero2W, cm3, cm3+, cm4, 5

Preparation

  1. Download the Alpine for Raspberry Pi tarball. Use the compability list above when choosing image/file to download.
  2. Create a bootable FAT32 partition on your SD card. The partitioning and formatting part of the instructions on the linked page could be done using a graphical partitioning tool such as gnome-disks, just make sure the partition type is W95 FAT32 (LBA). (The current type can be found in the "Type" column in the output of fdisk -l.)
  3. Extract the tarball to the root of the bootable FAT32 partition.

To setup a headless system, a bootstrapping configuration overlay file headless.apkovl.tar.gz may be added to enable basic networking, so that following configuration steps can be performed under ssh. Pi Zero may be configured with simple USB ethernet-gadget networking with another computer sharing its internet connection.

It is recommended to create a usercfg.txt file on boot partition to configure low-level system settings, as config.txt may be replaced during bootloader/system upgrades: details can be found here.
However, note some settings can only be set in config.txt, and will have no effect when specified in usercfg.txt (e.g. gpu_mem). Some interesting values include:

  • To enable the UART console: enable_uart=1
  • To enable audio: dtparam=audio=on
  • By default system will use legacy video driver: some options may be used to adjust displays modes (e.g. if you see black edges around your screen after booting the Pi, you can add disable_overscan=1). Alternatively Linux DRM-KMS driver may be used (see below).
  • If you plan to install on a Pi Compute Module 4 with I/O board, you may need to add: otg_mode=1

Recent versions include Broadcom firmware files. If you're using an older Alpine version, see section below.

Installation

Follow these steps to install Alpine Linux in Diskless Mode:

  1. Insert the SD card into the Raspberry Pi and power it on
  2. Login into the Alpine system as root. Leave the password empty.
  3. Check the current date and time by issuing date. Correct if necessary by issuing date -s YYYYMMDDhhmm.
  4. Type setup-alpine
  5. Once the installation is complete, commit the changes by typing lbu commit -d

Type reboot to verify that the installation was indeed successful.

Post Installation

Update the System

After installation, make sure your system is up-to-date:

apk update apk upgrade

Don't forget to save the changes:

lbu commit -d

Note: this does not upgrade the kernel. In order to upgrade the kernel, a full upgrade of the Alpine Linux version must be performed as described in upgrading Alpine Linux for removable media.

Linux Kernel Graphics Modes

By default system configuration will use legacy video driver: this driver has some limitations and is lacking support.
It is recommended to enable Linux DRM-KMS driver by adding the following to usercfg.txt: 

# Enable DRM VC4 V3D driver
dtoverlay=vc4-kms-v3d
max_framebuffers=2

# Don't have the firmware create an initial video= setting in cmdline.txt.
# Use the kernel's default instead.
disable_fw_kms_setup=1

Note: This overlay disables legacy video options.

Install the Mesa drivers (Pi4 and Pi5):

apk add mesa-dri-gallium

Then reboot:

lbu_commit -d; reboot

Wireless drivers

As of Alpine 3.17, Wifi and Bluetooth drivers are available within install image: they are part of linux-firmware-brcm (and linked dependencies).
Since kernel 6.1.25 (i.e. Alpine 3.18), onboard bluetooth is enabled & autoprobed by default (it may be disabled by setting krnbt off).

Troubleshooting

raspinfo utility can be used as a first step to diagnose issues: it will make a log report of essential Pi system configuration, and is often used as a reference to submit questions or bug reports within Raspberry Pi community (Forums, Github, etc).
It can be installed with raspberrypi-utils-raspinfo subpackage.

Long boot time when running headless

If no peripherals are connected, the system might hang for an exceptionally long period of time while it attempts to accumulate entropy.

If this is the case, simply plugging in any USB device should work around this issue, since it increases the amount of entropy available to the kernel via interrupts.

apk indicating 'No space left on device'

Note some models of the Raspberry Pi such as the 3A+ only have 512M of RAM, which on fresh Alpine deployment will only leave around 200M for tmpfs root. It's important to keep this limitation in mind when using these boards.

Clock-related error messages

During the booting time, you might notice errors related to the hardware clock. Many Raspberry Pi do not have a hardware clock, or may have one without battery, in which case the behaviour depends on whether you physically cut power or not.

Also, setup-alpine will adapt the installation to the type of Raspberry Pi you use, which means for example that on a RPI5, you will see hwclock> service, whereas on a RPI4 it will use swclock. In doubt, make sure to do the installation on the target hardware.

If you still experience clock errors, add the following line to /etc/chrony/chrony.conf:

makestep 0.1 3

Persistent storage

Traditional disk-based (sys) installation

This material is proposed for merging ...

It should be merged with Classic install or sys mode on Raspberry Pi. There's an existing page for sys-installations on RasPi. (Discuss)

It is also possible to switch to a fully disk-based installation. This is not yet formally supported, but can be done somewhat manually. This frees all the memory otherwise needed for the root filesystem, allowing more installed packages.

Split your SD card into two partitions: the FAT32 boot partition described above (in this example it'll be mmcblk0p1) , and a second partition to hold the root filesystem (here it'll be mmcblk0p2). Boot and configure your diskless system as above, then create a root filesystem:

apk add e2fsprogs mkfs.ext4 /dev/mmcblk0p2

Now do a disk install via a mountpoint. The setup-disk script will give some errors about syslinux/extlinux, but you can ignore them. The Raspberry Pi doesn't need them to boot.

mkdir /stage mount /dev/mmcblk0p2 /stage setup-disk -o /media/mmcblk0p1/MYHOSTNAME.apkovl.tar.gz /stage # (ignore errors about syslinux/extlinux)

Add a line to /stage/etc/fstab to mount the Pi's boot partition again:

/dev/mmcblk0p1 /media/mmcblk0p1 vfat defaults 0 0

Now add a root=/dev/mmcblk0p2 parameter to the Pi's boot command line, either cmdline-rpi2.txt or cmdline-rpi.txt depending on model:

mount -o remount,rw /media/mmcblk0p1 sed -i '$ s/$/ root=\/dev\/mmcblk0p2/' /media/mmcblk0p1/cmdline-rpi2.txt

You might also consider overlaytmpfs=yes here, which will cause the underlying SD card root filesystem to be mounted read-only, with an overlayed tmpfs for modifications which will be discarded at shutdown.

N.B. the contents of /boot will be ignored when the Pi boots. It will use the kernel, initramfs, and modloop images from the FAT32 boot partition. To update the kernel, initfs or modules, you will need to manually (generate and) copy these to the boot partition or you could use bind mount, in which case, copying the files to boot partition manually, is not needed.

echo /media/mmcblk0p1/boot /boot none defaults,bind 0 0 >> /etc/fstab

Loopback image with overlayfs

When you install Alpine in diskless mode, the entire system is loaded into memory at boot. If you want additional storage (for example, if you need more space than offered by your RAM) we need to create loop-back storage onto the SD card mounted with overlayfs.

First, make the SD card writable again and change fstab to always do so:

mount /media/mmcblk0p1 -o rw,remount sed -i 's/vfat\ ro,/vfat\ rw,/' /etc/fstab

Create the loop-back file, this example is 1 GB:

dd if=/dev/zero of=/media/mmcblk0p1/persist.img bs=1024 count=0 seek=1048576

Install the ext utilities:

apk add e2fsprogs

Format the loop-back file:

mkfs.ext4 /media/mmcblk0p1/persist.img

Mount the storage:

echo "/media/mmcblk0p1/persist.img /media/persist ext4 rw,relatime,errors=remount-ro 0 0" >> /etc/fstab mkdir /media/persist mount -a

Make the overlay folders, we are using the /usr directory here, but you can use /home or anything else.

Warning: Overlay workdir needs to be an empty directory on the same filesystem mount as the upper directory. So each overlay must use its own workdir.



mkdir /media/persist/usr mkdir /media/persist/.work_usr echo "overlay /usr overlay lowerdir=/usr,upperdir=/media/persist/usr,workdir=/media/persist/.work_usr 0 0" >> /etc/fstab mount -a

Your /etc/fstab should look something like this:

/dev/cdrom /media/cdrom iso9660 noauto,ro 0 0 /dev/usbdisk /media/usb vfat noauto,ro 0 0 /dev/mmcblk0p1 /media/mmcblk0p1 vfat rw,relatime,fmask=0022,dmask=0022,errors=remount-ro 0 0 /media/mmcblk0p1/persist.img /media/persist ext4 rw,relatime,errors=remount-ro 0 0 overlay /usr overlay lowerdir=/usr,upperdir=/media/persist/usr,workdir=/media/persist/.work_usr 0 0

Now commit the changes: (optionally remove the e2fsprogs, but it does contain repair tools)

lbu_commit -d

Remember, with this setup if you install things and you have done this overlay for /usr, you must not commit the 'apk add', otherwise, while it boots it will try and install it to memory, not to the persistent storage.

If you do want to install something small at boot, you can use apk add and lbu commit -d.

If it is something a bit bigger, then you can use apk add but then not commit it. It will be persistent (in /user), but be sure to check everything you need is in that directory and not in folders you have not made persistent.

Netboot

Netbooting Raspberry Pi 4

The Raspberry Pi 4 bootloader can be configured to boot from the network [1]. Configure the bootloader with at least

BOOT_ORDER=0xf142 TFTP_PREFIX=1

and optionally also

TFTP_IP=x.x.x.x

where x.x.x.x is the IP address of your TFTP server.

If not configuring TFTP_IP in the bootloader, you'll need to configure your DHCP server to advertise the TFTP server IP address. This varies depending on your DHCP server; use the following details if applicable:

  1. Vendor class: PXEClient:Arch:00000:UNDI:002001
  2. Filename: /

The minimal set of files that your TFTP server needs to host are:

  1. bcm2711-rpi-4-b.dtb (from raspberrypi/firmware/master/boot/bcm2711-rpi-4-b.dtb)
  2. cmdline.txt (see below)
  3. config.txt (see below)
  4. fixup4.dat (from raspberrypi/firmware/master/boot/fixup4.dat, alternatively fixup4cd.dat for the cut down version)
  5. initramfs-rpi4 (from alpine/edge/releases/aarch64/netboot/initramfs-rpi4)
  6. start4.elf (from raspberrypi/firmware/master/boot/start4.elf, alternatively start4cd.elf for the cut down version)
  7. vmlinuz-rpi4 (from alpine/edge/releases/aarch64/netboot/vmlinuz-rpi4)

config.txt:

[pi4] kernel=vmlinuz-rpi4 initramfs initramfs-rpi4 arm_64bit=1

cmdline.txt:

modules=loop,squashfs console=ttyAMA0,115200 ip=dhcp alpine_repo=http://dl-cdn.alpinelinux.org/alpine/edge/main modloop=http://dl-cdn.alpinelinux.org/alpine/edge/releases/aarch64/netboot/modloop-rpi4

Instead of using the http://dl-cdn.alpinelinux.org/alpine/edge/releases/aarch64/netboot/ base URL above, pinning to a specific point in time is preferred. Raspberry Pi 4 netboot files are available from https://dl-cdn.alpinelinux.org/alpine/edge/releases/aarch64/netboot-20230329/ onward.

With the above configured the Raspberry Pi 4 should be able to boot from the network without an SD card.

Wireless support with older Alpine images

In Alpine 3.14, the WiFi drivers for the Raspberry Pi were moved from linux-firmware-brcm to the linux-firmware-cypress package (source?). Since the images seem to be an outdated version of the former, Wi-Fi will work during installation, but after the first update it will break. Use the ethernet interface to download the required packages:

apk add linux-firmware-cypress

And reboot.

If you need Wi-Fi, you'll need to download the latest Broadcom drivers to your SD card. (Replace /mnt/sdcard with the correct mount point.) 

 git clone --depth 1 https://github.com/RPi-Distro/firmware-nonfree.git
 cp firmware-nonfree/brcm/* /mnt/sdcard/firmware/brcm

Enable the Serial Console

Besides having enable_uart=1 in usercfg.txt, the kernel command-line option console needs to be changed to console=serial0,115200 in cmdline.txt.

From a Linux desktop, connect to it with something like this:

cu -l /dev/ttyUSB0 -s 115200

See Also

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