MDEV-15207: mysql_upgrade cannot create file mysql_upgrade_info

man/mysql_upgrade.1

 '\" t
 .\"
-.TH "\FBMYSQL_UPGRADE\FR" "1" "14/12/2015" "MariaDB 10\&.1" "MariaDB Database System"
+.TH "\FBMYSQL_UPGRADE\FR" "1" "20 July 2020" "MariaDB 10\&.1" "MariaDB Database System"
 .\" -----------------------------------------------------------------
 .\" * set default formatting
 .\" -----------------------------------------------------------------
@@ -165,6 +165,8 @@ in the data directory\&. This is used to quickly check whether all tables have b
 \fB\-\-force\fR
 option\&.
 .PP
+For this reason, \fBmysql_upgrade\fR needs to be run as a user with write access to the data directory\&.
+.PP
 If you install MariaDB from RPM packages on Linux, you must install the server and client RPMs\&.
 \fBmysql_upgrade\fR
 is included in the server RPM but requires the client RPM because the latter includes