Diskless Mode
In Diskless mode the entire operating system with all applications are first loaded into RAM and then only run from there. This is the method already used to boot the Alpine Linux iso installation images. Alpine Linux can be installed and configured so that the system continue to boot like this if "disk=none" is specified while running the setup-alpine script.
The mode is extremely fast and can save on unnecessary disk spin-ups, power, and wear. It is similar to what other linux distributions may call a "frugal" install or boot into with a "toram" option.
Custom configurations and package installations may optionally still be preserved or "persist" across reboots by using the Alpine local backup tool lbu. It enables committing and reverting system states by using .apkovl files that are saved to customizable boot device, a writable storage and loaded when booting. If additional or updated packages have been added to the system, these may also be made available for automatic (re)installation during the boot phase without any (re)downloading, by enabling a local package cache on the writable storage.
Installation
Following the Installation steps to complete the base configuration completes the pre-setup of "diskless" Alpine Linux system.
If a writable partition is available, setup-alpine can be told to store the configs and the package cache on that writable partition. (Later, another directory on that same partition or another available partition may also be mounted as /home, or for example, for selected important applications to keep their run-time and user data on it.)
Alternately, use the setup-lbu script to configure a "local backup" location for the diskless system, and lbu commit to then save the local configuration state.
The boot device of the newly configured local "diskless" system may remain the initial (and possibly read-only) installation media. But it is also possible to copy the boot system to a partition (e.g. /dev/sdXY) with setup-bootable script and create a customizable boot device.
Refer Saving and loading ISO image customizations related to loading an .apkovl volume from system partitions.
As per Bug: #10473 Storing local configs and the package cache on internal disks requires manual steps to have the partition listed, i.e. making a /etc/fstab entry, mountpoint, and mount, *before* running setup-alpine. The linked workaround also still requires to commit these configurations to disk manually before rebooting.
As per Bug: #11589. The APKOVL loading of diskless setups doesn't work on btrfs and xfs filesystems, or nvme-based devices => So, for the moment, use only ext4 filesystem partitions on classic drives to store diskless mode states.
- The following creates an ext4 partition with disabled journaling, to reduce write operations and allow the disk to spin down after the .apkovl and the packages have been read from the partition during the boot.
# mkfs.ext4 -O ^has_journal /dev/sdXY # the "-O ^has_journal" DISABLES journaling ("^" means "not")