# How do Ign and Hit affect apt-get update?

My understanding of Ign and Hit which are displayed in the output of the command apt-get update is that Hit: File found. No change in its timestamp and Ign: File ignored. No change in its content..

What does this mean exactly? For example if a package is to be upgraded does it mean that its timestamp has changed as has its contents?

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From what I can see in the apt source code, "Ign" means there was an error retrieving the file, but the error is being ignored. When I run apt-get update, I see 3 Ign messages, all of which are for Translation-en files. A packet dump shows that the requests for those files got HTTP 404 responses.
"Hit" on the other hand means exactly what you said. The file was found on the server and it hasn't been changed since the last time it was downloaded. This is indicated by HTTP code 304. Note that we're not talking about timestamps on individual packages, sinceapt-get update doesn't download those. It downloads the list of available packages and other related information. The timestamps being compared are on those list files, not the packages themselves.
What do you mean by "the error is being ignored"? I also take it that a Hit indicates that I have a copy of the latest list since apt-get update was last run. Is that correct? –  PeanutsMonkey Jul 30 '12 at 20:24
The error is being ignored because it is an error in downloading a non-essential file. Hit means the old copy in your cache matches the current one on the server. –  Alan Curry Jul 30 '12 at 20:52