How k8s invokes or provides services across namespaces

how to invoke services across namespaces, do you need any permissions?
or can services be provided across command spaces? How to configure it?

I want to deploy generic services to a separate namespace, not one per space.

K8s
Mar.17,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b334b9-2be89.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b334b9-2be89.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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