Add browsers to profile-sync-daemon on my own

Profile-sync-daemon

Profile-sync-daemon is a script that relocates browser profiles from the drive to the RAM disk. A browser profile is the files that is read/written at runtime, such as browser settings (including bookmarks and extensions), cookies, etc. It is often about 100 MB or more for an ordinary browser.

By using profile-sync-daemon(psd), you will get faster operation and less I/O to the SSD (that makes SSD live longer!).

As you can see from the high praise on the Arch wiki, it was created by one of the Arch Linux developer, so if you are using an Arch distribution, there is no reason not to use it. Of course, official packages are available for many major distributions such as Debian, Ubuntu, Fedora, and Gentoo, in addition to Arch.

How to use

Arch can install it from official extra repo by pacman.

$ sudo pacman -S profile-sync-daemon

Edit the config file.

$ nano ~/.config/psd/psd.conf

Add the browsers in the parentheses of BROWSERS, separating by spaces. Supported browsers are limited to those listed under Possible values:.

BROWSERS=(firefox icecat chromium)

It is controlled by systemd. Make sure do it with --user.

$ systemd --user start psd.service
$ systemd --user enable psd.service

You can check how much memory is actually being used by psd preview.

Add browsers on your own

Here’s the main point. Add browsers that is not supported by psd. Please be aware that future updates may destroy your environment, so please do so at your own risk.

Psd specification

Looking at the source code, it seems that a shell script for each browser is placed in /usr/share/psd/browsers and that it is executed after checking for the existence of a file with the same name as the argument of BROWSERS.

This could be applied by simply putting my own shell scripts in /usr/share/psd/browsers. I really appreciate this kind of design, because I don’t have to build, package, and install it myself.

if [[ -d "$HOME"/.mozilla/firefox ]]; then
    index=0
    PSNAME="$browser"
    while read -r profileItem; do
        if [[ $(echo "$profileItem" | cut -c1) = "/" ]]; then
            # path is not relative
            DIRArr[$index]="$profileItem"
        else
            # we need to append the default path to give a
            # fully qualified path
            DIRArr[$index]="$HOME/.mozilla/firefox/$profileItem"
        fi
        (( index=index+1 ))
    done < <(grep '[Pp]'ath= "$HOME"/.mozilla/firefox/profiles.ini | sed 's/[Pp]ath=//')
fi

check_suffix=1

Check Firefox specification

Note that the profile specifications have changed since Firefox-ESR 140.0

Since all the browsers to be added this time are Firefox-based, check the Firefox profile specifications.

Information on where the profiles are located and which one is currently applied can be found at about:profiles.

Information for managing profiles is compiled in the file profile.ini in the directory where the profiles are located.

profiles.ini

[Profile1]
Name=default
IsRelative=1
Path=lekocygz.default
Default=1

[Profile0]
Name=default-release
IsRelative=1
Path=wymt0yba.default-release

[General]
StartWithLastProfile=1
Version=2

[Install3B6073811A6ABF12]
Default=wymt0yba.default-release
Locked=1

The profile usually used is default-release, where default is the profile in the old specification, and is meant to be a backup in case of emergency.

Firefox seems to distinguish multiple profiles by their suffix like default-release-1, which requires check_suffix=1 in the shell script.

if [[ -d "$HOME"/.mozilla/firefox-esr ]]; then
    index=0
    PSNAME="$browser"
    while read -r profileItem; do
        if [[ $(echo "$profileItem" | cut -c1) = "/" ]]; then
            # path is not relative
            DIRArr[$index]="$profileItem"
        else
            # we need to append the default path to give a
            # fully qualified path
            DIRArr[$index]="$HOME/.mozilla/firefox-esr/$profileItem"
        fi
        (( index=index+1 ))
    done < <(grep '[Pp]'ath= "$HOME"/.mozilla/firefox-esr/profiles.ini | sed 's/[Pp]ath=//')
fi

check_suffix=1

if [[ -d "$HOME"/.librewolf ]]; then
    index=0
    PSNAME="$browser"
    while read -r profileItem; do
        if [[ $(echo "$profileItem" | cut -c1) = "/" ]]; then
            # path is not relative
            DIRArr[$index]="$profileItem"
        else
            # we need to append the default path to give a
            # fully qualified path
            DIRArr[$index]="$HOME/.librewolf/$profileItem"
        fi
        (( index=index+1 ))
    done < <(grep '[Pp]'ath= "$HOME"/.librewolf/profiles.ini | sed 's/[Pp]ath=//')
fi

check_suffix=1

BROWSERS=(librewolf firefox icecat chromium)

$ systemctl --user stop psd
$ systemctl --user start psd

Conclusion

If you do it, you really do it at your own risk please.

Changelog

2026-9-23 : Removed incorrect information that “psd also synchronizes the cache” While the cache is also stored on tmpfs, it is located in a different place from the profile directory, and psd is not involved.

2025-10-17 : Fixed typo and some misunderstaindings about cache. The incorrect explanation stating “browser profile is the files … cache, cookies, etc.” has been corrected. Cookies are included in the profile directory, but cache is stored in a separate cache directory ($HOME/.cache/mozilla/firefox in Firefox) distinct from the profile.

2025-07-06 : Just after I wrote this article, the Firefox-ESR 140.0 was released, and the profile directory was changed from ~/.mozilla/firefox-esr to ~/.mozilla/firefox. That means, psd can handle ESR just by entering BROWSERS=(firefox) in the config. Please be sure to check the directory where the profile is located before working on it. And please keep conscious on current specification and read release notes carefully to prepare changes in the future.