strongly encourage Linux users to not make /etc/mtab a flat file

The OpenRC team does not currently know of any modern linux tools that
require /etc/mtab to be a flat file, so this puts users on notice that
the mtab service will be removed in the future.

NEWS.md

@@ -3,6 +3,21 @@
 This file will contain a list of notable changes for each release. Note
 the information in this file is in reverse order.
 
+## OpenRC 0.35
+
+Consider this your second notification with regard to /etc/mtab being a
+file instead of a symbolic link.
+
+In this version, the mtab service will complain loudly if you have
+mtab_is_file set to yes and recommend that you change this to no and
+restart the mtab service to migrate /etc/mtab to a symbolic link.
+
+If there is a valid technical reason to keep /etc/mtab as a flat file
+instead of a symbolic link to /proc/self/mounts, we are interested and
+we will keep the support in that case. Please open an issue and let us
+know however. Otherwise, consider this your final notice that the mtab
+service will be removed in the future.
+
 ## OpenRC 0.33
 
 This version removes the "service" binary which was just a copy of

conf.d/mtab

@@ -1,5 +1,13 @@
+# As far as we are aware, there are no modern linux tools or use cases
+# which require /etc/mtab to be a separate file from /proc/self/mounts,
+# so this setting should be commented out.
+# If it is set to yes, please comment it out and run this command:
+# # rc-service mtab restart
+# In the future, the mtab service will be removed since we are not aware
+# of any need to manipulate /etc/mtab as a separate file from
+# /proc/self/mounts.
+# If you have a technical reason we should keep this support, please
+# open an issue at https://github.com/openrc/openrc/issues and let us
+# know about your situation.
 # This setting controls whether /etc/mtab is a file or symbolic link.
-# Most of the time, you shouldn't touch this. However, if the default
-# breaks your system in some way, please see the NEWS.md file that comes
-# with OpenRC for the actions to take.
 # mtab_is_file=no

init.d/mtab.in

@@ -31,6 +31,10 @@ start()
 		einfo "Creating mtab symbolic link"
 		ln -snf /proc/self/mounts /etc/mtab
 	else
+		ewarn "The ${RC_SVCNAME} service will be removed in the future."
+		ewarn "Please change the mtab_is_file setting to no and run"
+		ewarn "# rc-service mtab restart"
+		ewarn "to create the mtab symbolic link."
 		[ -L /etc/mtab ] && ewarn "Removing /etc/mtab symbolic link"
 		rm -f /etc/mtab
 		einfo "Creating mtab file"