For the last week or more, running
sudo apt-get update culminates in error:
Reading package lists... Done E: Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/xenial/main/dep11/Components-amd64.yml Could not open file /var/lib/apt/lists/partial/au.archive.ubuntu.com_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz - open (13: Permission denied) [IP: 220.127.116.11 80] E: Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/xenial-backports/main/dep11/icons-64x64.tar Could not open file /var/lib/apt/lists/partial/au.archive.ubuntu.com_ubuntu_dists_xenial-backports_main_dep11_icons-64x64.tar.gz - open (13: Permission denied) [IP: 18.104.22.168 80] E: Some index files failed to download. They have been ignored, or old ones used instead.
Entering either of the 2 specified urls into a browser address bar results in a 'File not found' (404) error - but if I append
.gz to both addresses, then the respective files can be downloaded.
However, having downloaded the 2 files, I then don't know how (or if) I can utilize them.
Seeking advice on how best to proceed.