ramroot

ramroot is a mkinitcpio hook that loads the root filesystem to a zram device during the initramfs boot stage.

Installation

Install hook, manpages, libs, config, issue:

# make install

Uninstall:

# man uninstall

Also available on the AUR.

After installation, the ramroot hook must be manually added to /etc/mkinitcpio.conf (or a file in /etc/mkinitcpio.conf.d/). This was done via script in the past (before I realized it's not a good idea to change users' /etc/mkinitcpio.conf in an install script).

Ramroot is not (yet) compatible with a systemd based initramfs. See the non-systemd hooks in the official meson.build from mkinitcpio. Using these hooks with ramroot added after udev enables ramroot:

HOOKS=(base udev ramroot autodetect microcode modconf kms keyboard keymap consolefont block filesystems fsck)

The drop-in file mkinitcpio.ramroot.conf is provided that can be placed in /etc/mkinitcpio.conf.d/ to easily make these changes.

Rebuild initramfs to include changes:

# mkinitcpio -P

Users are responsible for dealing with their own /etc/mkinitcpio.conf and any .pacnew files resulting from system updates.

Configuration

/etc/ramroot.conf

ash shell script setting the following values:

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.

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 filesystem. 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.

Any files copied from /etc/ramroot.z/ to / in this manner preserve all ownerships. Be wary that 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 for /etc/ramroot.z/ above.

Requirements

• Arch Linux
• mkinitcpio

gpl3 | mags