Using /dev/shm with Librewolf 
Fri, 19 Dec 2025 07:26:23 +0100
+-----------------------------------------------------------------+

I recently  upgraded my  laptop to  16Gb RAM  which is  pretty much
overkill but I  wanted to use it  for tmpfs which will  make my SSD
happy as less write cycles when writing to /tmp.

Since  kernel 2.6  there's another  advantage: /dev/shm  which acts
like a  ram disk. One  of the  most ressource heavy  applications I
have  is  my  GUI  browser,  Librewolf. It  turns  out  I  can  put
Librefox's profile  into /dev/shm as  long as I remember  to backup
when shutting  down, and restore it  when booting up. My  SSD is so
happy with this as again it cuts  down the write cycles, and RAM is
around 1000 times faster than the SSD.

Notes ------
** Both /dev/shm and tmpfs are used for temporary file storage, but 
/dev/shm is specific to Linux and  is  typically  used  for  shared 
memory, while tmpfs can be used more generally for temporary files.

** In FreeBSD unlike Linux /dev/shm is used  for  special purposes.
If /tmp is mounted as tmpfs you can use this instead.

** Librewolf doesn't use a disk cache by default. Check 
about:cache?storage=disk if you are using another  Firefox  variant
and either disable or set it to use /dev/shm too, unless  you  have
massive cache requirements that depass available RAM space.
----- /Notes 

In Librewolf I checked about:support to see my profile directory.
I copied this profile in ~/.librewolf  to /dev/shm:

mkdir /dev/shm/librewolf-profile

cp -R ~/.librewolf/XXXXXXXX.default-release \
~/librewolf/XXXXXXXX.default-release_BACKUP

cp -R ~/.librewolf/XXXXXXXX.default-release \
/dev/shm/librewolf-profile/XXXXXXXX.default-release

rm -r ~/.librewolf/XXXXXXXX.default-release

ln -s /dev/shm/librewolf-profile/XXXXXXXX.default-release \
~/.librewolf/XXXXXXXX.default-release

all well and good, but RAM  is volatile, the profile will dissapear
between reboots.

so I have two scripts to backup and restore:

#!/usr/bin/env bash
#lw-backup
rsync -a --delete /dev/shm/firefox-profile/ \
/home/philip/.librewolf/XXXXXXXX.default-release_BACKUP/

#!/use/bin/env bash 
#lw-restore 
mkdir -p /dev/shm/librewolf-profile
rsync -a /home/philip/.librewolf/XXXXXXXX.default-release_BACKUP/ \
/dev/shm/librewolf-profile/

Both scripts must be in my PATH, for example .local/bin

I use Artix Linux with dinit and the DWM  windowmanager.  Login  is
managed with XDM. So I can add lf-restore to my .xinitrc

Dinit doesn't  manage shutdown  scripts, but I  have a  dmenu panel
that  calls  a script  for  logout,  suspend, hibernate,  lock  and
poweroff. So I added lf-backup to this script.

#!/usr/bin/env bash

# save librewolf ram profile to disk
$HOME/.local/bin/lf-save.sh

case $1 in
	shutdown)
		loginctl poweroff
	;;
	reboot)
		loginctl reboot		
	;;
	logout)
		pkill -u $USER
	;;
	lock)
		slock
	;;
	suspend)
		loginctl suspend
	;;
	hibernate)
		loginctl hibernate
	;;
	*)
		echo "unknown command"
	;;
esac


Voila.



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