This bug is derived from the bug 276547. I would add the update made by the developer MJ to the glabel man page ('man 8 glabel') under the following paragraph: label Set up a label name for the given provider. ... ... It would be useful for the FreeBSD community. Thanks.
Created attachment 248538 [details] patch for glabel man page Adding a patch - suggesting to add a paragraph that outlines the requirement to either not have a device's file system mounted or in read-only mode to be able to persist changes.
Added a Phabricator review to simplify the patch creation and review: https://reviews.freebsd.org/D44394