Snaps update automatically, and by default, the snapd daemon checks for updates 4 times a day. Each update check is called a refresh and is described in more detail in Managing updates.
A refresh can sometimes occur when a snapped application is running, and this can be problematic for desktop applications. A desktop application may stop responding, or the user may remain unaware that an application needs an update, which adds unnecessary risk if an update is triggered by a known vulnerability or stability issue.
Service management is not affected, as services are started and stopped manually as part of the refresh process, unless a specific endure value has been embedded into the snap by the snap developer. See Services and daemons for further details.
When an update occurs while an affected desktop application is running, refresh app awareness helps to mitigate any potential issues in two ways:
Refresh app awareness requires snapd version 2.57 or greater. It was previously available as an experimental feature.
Deferred updates
An update can be postponed for up to 14 days if an affected application is running. The update will be either applied when the next refresh occurs without the application running, or after 14 days even if the application remains active.
After closing the affected application, the refresh can be triggered manually with the snap refresh command, either globally for all snaps, or with the specific snap name:
snap refresh <snap-name>
If a manual refresh detects the application is still running, the error output will include the detected process ids of the running applications:
error: cannot refresh "firefox": snap "firefox" has running apps (firefox), pids:
1639,1854,1912,1932,3514,3632,5814,5870
Desktop notifications
While an affected application is running, each refresh attempt will trigger a desktop notification to inform the user that the app should be closed to avoid disruption:
On the default Ubuntu GNOME desktop, notifications can be modified and disabled by selecting Notifications from the Settings application and selecting the Snapd User Session Agent application:
Other desktop environments have equivalent functionality.
See Refresh awareness security policy for details on how refresh updates accommodate confinement and security policy requirements.