Refreshing snapd on core18, if core18 image is very old, fails due to read-only /etc/dbus-1/session.d
$ /snap/snapd/9169/usr/bin/snap change 41
Status Spawn Ready Summary
Done today at 15:01 UTC today at 15:03 UTC Ensure prerequisites for "snapd" are available
Undone today at 15:01 UTC today at 15:03 UTC Download snap "snapd" (9612) from channel "latest/stable"
Done today at 15:01 UTC today at 15:02 UTC Fetch and check assertions for snap "snapd" (9612)
Undone today at 15:01 UTC today at 15:02 UTC Mount snap "snapd" (9612)
Undone today at 15:01 UTC today at 15:02 UTC Run pre-refresh hook of "snapd" snap if present
Undone today at 15:01 UTC today at 15:02 UTC Stop snap "snapd" services
Undone today at 15:01 UTC today at 15:02 UTC Remove aliases for snap "snapd"
Error today at 15:01 UTC today at 15:02 UTC Make current revision for snap "snapd" unavailable
Undone today at 15:01 UTC today at 15:02 UTC Copy snap "snapd" data
Undone today at 15:01 UTC today at 15:02 UTC Setup snap "snapd" (9612) security profiles
Error today at 15:01 UTC today at 15:02 UTC Make snap "snapd" (9612) available to the system
Hold today at 15:01 UTC today at 15:02 UTC Automatically connect eligible plugs and slots of snap "snapd"
Hold today at 15:01 UTC today at 15:02 UTC Set automatic aliases for snap "snapd"
Hold today at 15:01 UTC today at 15:02 UTC Setup snap "snapd" aliases
Hold today at 15:01 UTC today at 15:02 UTC Run post-refresh hook of "snapd" snap if present
Hold today at 15:01 UTC today at 15:02 UTC Start snap "snapd" (9612) services
Hold today at 15:01 UTC today at 15:02 UTC Remove data for snap "snapd" (8144)
Hold today at 15:01 UTC today at 15:02 UTC Remove snap "snapd" (8144) from the system
Hold today at 15:01 UTC today at 15:02 UTC Clean up "snapd" (9612) install
Hold today at 15:01 UTC today at 15:02 UTC Run health check of "snapd" snap
Done today at 15:01 UTC today at 15:03 UTC Consider re-refresh of "snapd"
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Make current revision for snap "snapd" unavailable
2020-10-13T15:02:56Z ERROR open /etc/dbus-1/session.d/snapd.session-services.conf.QJhd8TnncknL~: read-only file system
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Make snap "snapd" (9612) available to the system
2020-10-13T15:02:48Z ERROR open /etc/dbus-1/session.d/snapd.session-services.conf.hNRCSltnvDyy~: read-only file system
This is a real problem but it doesn't happen in regular circumstances. Still it has dire consequences, due to https:/