This page is about creating directly customizable boot devices. If you are looking for instructions on creating (flashing) read-only (iso9660 "CD" filesystem) images onto installation media, see the Installation page instead.

A directly customizable Alpine Linux boot medium is basically an Alpine system in diskless or data disk-mode installed to (and booting from) a device with a writable filesystem. It allows to also upgrade the kernel with its modules and firmware that is used to boot the system with the update-kernel script.

The more general local customizations, the configs (.apkovl) and the package cache, may of course also be stored on the same device, as long as the hardware is not being set to be write-locked by a hardware switch.

Requirements

An Alpine Linux CD-ROM or an .iso file containing the desired Alpine release (Download).
A device like an USB drive (flash, external HD, card reader, etc.) or a CF "CompactFlash", or SDcard.

Using setup-bootable

This is now the preferable method to create a directly customizable bootable device.

It consists an Installation of a diskless or data mode system with configs and package cache on the target device, and using the setup-bootable script to make the device bootable.

Manually copying Alpine files

This process applies to Alpine Linux 1.9.0 or later.

It describes how to manually create a custom (writable) USB boot device.

Copy ISO content to USB stick as individual files

Warning: We assume here sdU is your USB stick which would hold bootable Alpine Linux files.

The following procedure is for the Alpine Linux distribution itself, if you are using other Linux distro or other operating system you should know the best how to install syslinux and where mbr.bin file is located on your filesystem.

If you created a new partition above, format it with a FAT32 filesystem (replacing sdU with your device name):
apk add dosfstools
mkdosfs -F32 /dev/sdU1
Install syslinux and MBR (replacing sdU with your device name):
apk add syslinux
dd if=/usr/share/syslinux/mbr.bin of=/dev/sdU
syslinux /dev/sdU1
Copy the files to the boot device (replacing sdU with your device name):
mkdir -p /media/sdU1 mount -t vfat /dev/sdU1 /media/sdU1 cd /media/cdrom cp -a .alpine-release * /media/sdU1/ umount /media/sdU1
(Optional) Remove any apkovl files that were transfered as part of the copy process. This should be done if you wish to have a fresh install. Replace sdU with your device name)
mount -t vfat /dev/sdU1 /media/sdU1 rm /media/sdU1/*.apkovl.tar.gz umount /media/sdU1

Troubleshooting

Wrong Device Name

If you cannot boot from the boot device and you see something like:

Mounting boot media failed.
initramfs emergency recovery shell launched. Type 'exit' to continue boot

then it is likely that the device name in syslinux.cfg is wrong. You should replace the device name in this line:

append initrd=/boot/grsec.gz alpine_dev=usbdisk:vfat modules=loop,cramfs,sd-mod,usb-storage quiet

with the proper device name.

For boot from USB, the device name should be 'usbdisk' (as shown above)
For other options, you can run cat /proc/partitions to see the available disks (i.e. 'sda' or 'sdb')

Non-FAT32 Filesystems

Diskless and data mode booting

When the boot device is formatted with a filesystem other than those supported by default, the necessary initfs features need to be added to the modloop using update-kernel. See: Alpine_Linux_package_management#Upgrading_.22diskless.22_and_.22data.22_disk_mode_installs

Sys mode booting

Mount the boot device and edit the syslinux.cfg file.

Then locate the "append" line, and change the alpine_dev= setting to match the used filesystem and add the filesystem's kernel module to the modules= list.

For example, change

append [...] alpine_dev=usbdisk:vfat modules=loop,cramfs,sd-mod,usb-storage quiet

to

append [...] alpine_dev=usbdisk:ext4 modules=loop,cramfs,sd-mod,usb-storage,ext4 quiet

in the case of an ext4 formatted partition. (Or correspondingly for other filesystems, if they are supported by syslinux and the Alpine Linux kernel.)

Finishing installation

After one has booted the previously created Alpine Linux bootable USB medium, one has to prepare USB stick to hold local customizations and run setup-alpine to finish the installation.

First let's find out where is our just booted USB media mounted, the location could vary.

# mount | grep /media
/dev/sdU1 on /media/sdU1 type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=utf8,shortname=mixed,errors=remount-ro)

Create local directory on USB media to hold local APK cache (see APK Local Cache for details).

# mount -o remount,rw /media/sdU1
# mkdir /media/sdU1/cache
# setup-apkcache /media/sdU1/cache
# ls -l /etc/apk/cache
lrwxrwxrwx    1 root     root            17 Oct 19 13:16 /etc/apk/cache -> /media/sdU1/cache

Now run setup-alpine and proceed until a question about local disk selection - in diskless mode we won't use any disk (ie. our bootable media files is basically untouched) and we are going to use sdU1 to hold our system customization.

# setup-alpine
...
Which disk(s) would you like to use? (or '?' for help or 'none') [none] 
Enter where to store configs ('floppy', 'sdU1', 'usb' or 'none') [sdU1]: 
Enter apk cache directory (or '?' or 'none') [/media/sdU1/cache]:

After the installer finished you can see how many created/modified files are detected and will be added to the backup:

# lbu status
# lbu status | wc -l
59
# lbu commit
# ls -l /media/sdU1/*apkovl.tar.gz
-rwxr-xr-x    1 root     root          9591 Oct 19 15:23 /media/sdU1/foo.apkovl.tar.gz

Now all the customization are saved into the foo.apkovl.tar.gz compressed tarball on the USB stick itself.

Troubleshooting

Slow USB Devices

Specifying the 'waitusb=X' option at the end of the syslinux.cfg line might help with certain USB devices that take a bit longer to register. X stands for the amount of seconds kernel will wait before looking for the installation media.

append initrd=/boot/grsec.gz alpine_dev=usbdisk:vfat modules=loop,cramfs,sd-mod,usb-storage quiet waitusb=3

CF card readers

Some CF card readers have problems with the faster CF cards on the market. If you experience problems booting the CF card even after checking BIOS settings, you may need to use an older card.

Also, many CF card readers don't support DMA correctly, so you may need to add nodma to the append line of the syslinux.cfg file.