User specific font configuration does not survive snap updates

Metadata

Project: snapcraft (launchpad)
Number: #1948980
Type: issue
State: open
Author: ~gunnarhj
Labels: —
Created: 2021-10-27 07:17 PM UTC
Updated: 2021-11-17 09:35 AM UTC
Closed: —

Current evaluation

Snaps ignore $HOME fontconfig config and rewrite fonts.conf per revision; reporter later narrowed it to fonts.conf edits (conf.d files do persist) and suggests documenting the workaround. Untriaged since Nov 2021.

Suggested action: needs triage

Reason: The bug has no labels, no assignee and no maintainer response — only the reporter's own 2021-11-17 comments, which themselves downgrade it ("the importance of this issue is limited") and propose merely documenting the conf.d workaround. Code confirms the reported mechanism: extensions/desktop/common/init:44 sets XDG_CONFIG_HOME="$SNAP_USER_DATA/.config" and desktop-exports:328-329 rewrites "$XDG_CONFIG_HOME/fontconfig/fonts.conf" on every revision change (needs_update), so manual edits there are lost — but the reporter verified files in ../conf.d/ are copied to the new revision, i.e. a workaround exists. It also predates the move of this logic to snapcraft-desktop-integration (noted in extensions/desktop/common/fonts: "not used with the gnome extension for core22 and later"), so part of it now belongs to another repo. Uncertain whether honouring $HOME/.config/fontconfig is wanted at all, given the deliberate opposite decision in #4257, so a maintainer decision on scope is needed.

Evaluated by: mr-cal-bot

Impact: 38 Quick Win: 7 Complexity: 50 Confidence: 70 Actionability: 35

Issue body

After the merge of <https://github.com/snapcore/snapcraft/pull/3586>, the Firefox snap will hopefully soon see files in the /etc/fonts/conf.d directory. That directory basically consists of files (or symlinks) provided by packages installed on the host system. While it's possible for a user with admin privileges to add their own fontconfig config files to that directory, the natural place for user specific font configuration is $HOME. The user equivalent of /etc/fonts/conf.d is ~/.config/fontconfig/conf.d . fontconfig reads files in that directory as well as the file ~/.config/fontconfig/fonts.conf . But the instance of fontconfig used by the Firefox snap does not. Even if you can edit ~/snap/firefox/current/.config/fontconfig/fonts.conf or put files in ~/snap/firefox/current/.config/fontconfig/conf.d, your changes will be ignored as soon as the Firefox snap gets updated. This is an Ask Ubuntu question which points at the problem: https://askubuntu.com/questions/1368185/fontconfig-that-survives-firefox-snap-updates So we would need a way to make user specific font configuration persistent. While I wrote this bug with the Firefox snap in mind (since it has replaced the .deb by default in Ubuntu 21.10), I suppose this issue is a general snap issue. As an example it was mentioned for the Chromium snap at <https://forum.snapcraft.io/t/snap-package-cannot-read-fonts-conf/16657>.

Evaluation history

Date	Model	Scores	Action	Summary
2026-10-02 07:43 PM UTC	stealth/space-bunny-alpha	Impact: 38 Quick Win: 7 Complexity: 50 Confidence: 70 Actionability: 35	needs triage	Snaps ignore $HOME fontconfig config and rewrite fonts.conf per revision; reporter later narrowed it to fonts.conf edits (conf.d files do persist) and suggests documenting the workaround. Untriaged since Nov 2021.
2026-09-30 09:16 PM UTC	stealth/space-bunny-alpha	Impact: 42 Quick Win: 12 Complexity: 59 Confidence: 87 Actionability: 68	needs triage	Snap desktop apps such as Firefox ignore $HOME fontconfig configuration and overwrite revision-local fonts.conf; conf.d persists as a workaround, but the general behavior remains untriaged.
2026-09-24 07:52 PM UTC	stealth/space-bunny-alpha	Impact: 47 Quick Win: 11 Complexity: 65 Confidence: 89 Actionability: 64	needs triage	Fontconfig user configuration remains scoped to revision-specific snap data, with persistent ~/.config/fontconfig handling unimplemented and no maintainer triage recorded.
2026-09-01 09:30 AM UTC	qwen/qwen3.8-27b	Impact: 45 Quick Win: 11 Staleness: 88 Complexity: 75 Confidence: 70 Support Request: 10	needs triage	User fontconfig settings in ~/.config/fontconfig are ignored by Firefox/Chromium snaps and wiped on updates due to snapd's per-revision home directory. Open ~4.8 years, no labels, no maintainer response.
2026-07-23 02:11 PM UTC	qwen/qwen3.6-35b-a3b	Staleness: 95 Complexity: 70 Confidence: 80 Support Request: 10	close stale	User-specific fontconfig settings in ~/.config/fontconfig are ignored by Firefox and Chromium snaps, resetting on updates. The issue is over 4.5 years old with zero maintainer response or activity.
2026-07-22 02:45 PM UTC	qwen/qwen3.6-35b-a3b	Staleness: 95 Complexity: 60 Confidence: 85 Support Request: 10	close stale	User-specific fontconfig settings are ignored by the Firefox snap and lost on updates. The issue highlights a broader snap confinement limitation regarding persistent user configuration paths.
2026-07-10 06:04 AM UTC	qwen3.6-35b-a3b-mtp-q6	Staleness: 98 Complexity: 65 Confidence: 85 Support Request: 15	close stale	User-specific fontconfig settings in ~/.config/fontconfig/ are ignored by Firefox and other snaps, as changes in ~/snap/... are overwritten during updates. The issue highlights a persistence gap for user font configurations across snap revisions.

Update history

Date	Change
2021-11-17 09:35 AM UTC	created

Related work

Related To: snapcore/snapcraft#3586 (confidence 92%)
PR explicitly referenced in the issue body; merged as 407dc7551 and added the '<include ignore_missing="yes">conf.d</include>' in make_user_fontconfig.
Related To: snapcraft#4257 (confidence 85%)
Merged commit 7877ca5bb 'stop fontconfig from loading from host's /etc/fonts/conf.d' (LP #2025651) deliberately keeps host conf.d out of the snap, so the reporter's include-/etc/fonts/conf.d workaround runs against that decision.

Related issues

No related issues found above the similarity threshold.