An Ubuntu source update error and workaround

inrelease:clearsigned file isn ' t valid, got ' NODATA ' (Does the network require authentication?)

An attempt to make an apt update encountered the following error:

Reading Package List ... Complete
W:duplicate sources.list Entry Http://archive.ubuntukylin.com:10006/ubuntukylin/trusty/main amd64 Packages (/var/lib /apt/lists/archive.ubuntukylin.com:10006_ubuntukylin_dists_trusty_main_binary-amd64_packages)
W:duplicate sources.list Entry Http://archive.ubuntukylin.com:10006/ubuntukylin/trusty/main i386 Packages (/var/lib/ Apt/lists/archive.ubuntukylin.com:10006_ubuntukylin_dists_trusty_main_binary-i386_packages)
W: You may need to run Apt-get update to resolve these issues

The source of 163 has been used before and has never encountered this error, which occurred after installing several software from Ubuntukylin.

Directly in the system settings, software and updates, and other software to remove the source of all the Ubuntukylin (tick off) on the line, as for those software updates, forget about them.

An Ubuntu source update error and workaround