ramroot

Run Linux entirely from RAM! This is a customizable mkinitcpio hook that completely loads the root file system to a zram partition during the initramfs boot stage.

Usage

During early system boot, the ramroot initcpio hook determines the host machine's total ram and prompts the user y/n to load the root file system to zram if enough space is available.

A ramroot helper script easily enables/disables and/or generates additional ramroot config files.

Installation

This package is available in the AUR for easy installation. A basic config file is created during initial installation.

Requirements

Arch Linux

ramroot is designed specifically to work with the Arch Linux boot process. These scripts work with slight modifications on other distributions from time to time, however this not officially supported

mkinitcpio

Create custom initial ramdisk image.

Configuration

/etc/ramroot.conf

This file is an ash shell script. Many common bash builtins are not available here and the syntax tends to be a bit stricter. The fallback config file can be viewed at /usr/lib/ramroot/ramroot.conf.

After any changes are made to /etc/ramroot.conf, a user must execute ramroot -E or mkinitcpio -P in order for those changes to be built into a new initramfs image.

All UUID (or PARTUUID) values must include the proper UUID= prefix. A mountpath is an absolute mount path (as given in /etc/fstab). Every size is a whole number of mebibytes with no-suffix.

mounts_zram

Additional mounts loaded to zram when ramroot is active. A mount consists of the UUID separated from the mountpath by a colon. Multiple mounts are separated by spaces or newlines.

mounts_null

Mounts excluded when ramroot is active. The UUID is optional for these mounts. These will not be loaded to zram or mounted normally. If / is specified in mounts_null, ramroot will skip loading altogether.

ps_default

Default zram boot y/n prompt value. Valid values are yes or no.

ps_timeout

zram boot prompt timeout, positive integer between 1 and 32. After this many seconds, the prompt will select the ps_default value.

ram_min

Minimum amount of free ram required.

zram_min

Minimum amount of free zram required. If both this and ram_min cannot be satisfied, the zram boot prompt will automatically select no.

ram_pref

Preferred amount of free ram. Additional memory is allocated to ram up to this preferred value.

zram_max

Maximum amount of free zram. If ram_pref is satisfied, free zram is increased to zram_max.

All remaining memory is allocated towards ram.

/etc/ramroot.z/

The structure of this directory mirrors the hierarchy of the root file system. Upon a successful sync to zram, any files and directories contained in /etc/ramroot/ are non-persistently overwritten to the root directory.

This can be used to load any number of custom scripts, binaries, configs, etc when boot from zram. A few use case examples for this include: a custom zram hostname at /etc/ramroot.z/etc/hostname, enable autologin when boot from zram via a /etc/ramroot.z/etc/systemd/system/[email protected]/override.conf file, or even add more sudo access with drop in files in /etc/ramroot.z/etc/sudoers.d/.

Any files copied from /etc/ramroot.z/ to / in this manner preserve all ownerships. Be wary that any symbolic links (rather than their target files) will be overwritten by this action as they aren't resolved yet during early initramfs.

~/.ramroot.z/

Any files contained within a ~/.ramroot.z directory in a user's home folder are non-persistently overwritten to their home folders upon a sync to zram as described in /etc/ramroot.z/ above.

Ramroot Script

ramroot <options>

Options

-C, --config-gen

Attempt to detect the root file system partitions and generate a new config file.

-D, --disable

Remove ramroot hook from /etc/mkinitcpio.conf and rebuild initramfs image.

-E, --enable

Add ramroot hook to /etc/mkinitcpio.conf and rebuild initramfs image.

-o, --output <FILE>

Save new config to FILE instead of /etc/mkinitcpio.conf.

-Y, --yes

Overwrite output files without asking.

-H, --help

Display help text and exit.

Notes

The file system transfer to zram takes several minutes. As soon as the boot process is complete, the boot media can be safely removed.

Remember that all changes to files in zram are completely lost when the host machine is power cycled. To persistently update the system and edit files, boot the device without transferring the filesystem to zram.

Keep a clean and trimmed down system to maintain faster zram sync times. Arch Linux stores downloaded packages in /var/cache/pacman/pkg/. Consider removing old packages after system updates.

Higher quality (more expensive) USB flash drives exhibit a dramatic improvement in zram sync times.

Credits

This project was motivated greatly in part by the liveroot package and by several inquisitive forum posts.

Author

Chris Magyar

Version

2.0.2

License

GPL 3.0

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