[ubuntu-za] Failed to update repository information

Hilton Gibson hilton.gibson at gmail.com
Mon May 30 17:51:50 UTC 2011


On 30/05/2011 16:56, Lloyd Reijers wrote:
> On Sun, 2011-05-29 at 17:11 +0200, Robin Bownes wrote:
>> When I try to update repository information, I get the following error
>> message:
>> W:Failed to fetch
>> gzip:/var/lib/apt/lists/partial/za.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources  Hash Sum mismatch
>> , E:Some index files failed to download. They have been ignored, or
>> old ones used instead.
>
> Firstly, what does the error mean?
> A "hash sum" is often used when files are made available for download by
> an organisation. An algorithm (the hashing function) is run against the
> content of a file at the server side, which produces a hash sum. The
> file is made available for download, as well as its hash sum. A client
> may download the main file, and run the same hashing function on the
> downloaded file. If the client-side hash sum matches the server-side
> hash sum, then it's a fair assumption that the file that was downloaded
> matches the downloadable version on the server (and wasn't mangled in
> the download).
>
> Try it... Create a simple text file in your home directory with some
> content. Then drop to a command prompt (terminal). Run the program
>     you at pc:~$ md5sum ~/yourfile.txt
> This will output something along the lines of
>     62b6830c7a131d6a54c728a95f6dcb30  /home/you/yourfile.txt
> Now modify yourfile.txt (adding a simple new line character is enough to
> make it different enough to generate a completely different hash sum),
> and run the md5sum program again.
>     1a0a9976e3fd3e46c3bca3df60861fb4  /home/you/yourfile.txt
>
> So why _does_ the Hash Sum mismatch occur in your example?
> A few reasons, each with different fixes.
> 1. The organisation has just published the content for download, but
> they have not published the correct hash sum yet, as there may be a few
> moments between the main file and the hash sum file being made public.
> (Especially where mirror servers are involved).
> Solution: wait a while, and try again.
> Solution, corollary: switch server set (e.g. from south africa to main),
> update, switch back a few days later.
> 2. A proxy server _somewhere between you and the download host_ has
> cached the hash sum of an older version of the file, and though you're
> requesting the hash sum for the new file, you're being served the older
> one.
> Solution: execute
>     you at pc:~$ sudo apt-get update -o Acquire::http::No-Cache=True
>     you at pc:~$ sudo apt-get upgrade
> This -o flag instructs apt-get to send appropriate headers through in
> the http request telling cacheing proxy servers to mind their own
> business.
> 3. Your apt-get is confused (probably because of a bug, or disk
> corruption, or worse). You can remove all of the locally cached versions
> of the package files, gpg keys and hashes by removing the contents of
> the /var/lib/apt/lists folder. This will require a fresh download (via
> apt-get upgrade) of ALL of your package source information.
> NOTE: NEVER execute 'sudo rm -Rf /xxx' without understanding the
> command.
> Solution: execute
>     you at pc:~$ sudo rm -fR /var/lib/apt/lists/*
>     you at pc:~$ sudo apt-get upgrade
> 4. Double check the content of all the files in /etc/apt/sources.list.d/
> and the content of /etc/apt/sources.list and check for non-sequiturs.
> There may be archives you're requesting to check, but are old and
> outdated. Purge them (make a backup first in a different directory if
> you're nervous). If you're using natty, all your sources.list entries
> should be natty. If you're using maverick, all your sources.list entries
> should be maverick. You get the picture. (P.S. I've never seen this
> reason causing the warning you posted about though - It's just a last
> resort effort to solve the problem)
>
>> I often find the solutions to Ubuntu issues by Googling. In this
>> instance, I did not find a solution that I understood. I therefore
>> came to this list looking for assistance that I, as an ex-Windows, and
>> relatively inexperienced Ubuntu user could understand and use. I was
>> not looking for sarcasm or to be spoken to as if I am an idiot. There
>> are often impassioned discussions on this, and other Ubuntu lists,
>> regarding how to attract people to Ubuntu. I'm afraid that the general
>> tone, and lack of helpfulness of your reply are not what is needed in
>> this regard, and certainly not what I was looking for.
> Sigh. Step away from the drama triangle.
>
> The thing that you really should try to take from Raoul's email is the
> bit about 'maybe no-one has replied because it was not obvious that
> you'd done _any_ research', nor that you're a relatively inexperienced
> Ubuntu user. In general, pleas for help should be accompanied by a list
> of things you've attempted, as it helps those who're going to attempt to
> help you, and serves as a record for those who come after you and find
> your question (and hopefully result) via google etc. Further to that: If
> your issue is actually fixed by a mailing list query, it's useful to
> reply to the list that the issue is fixed and what you did.
>
> Anyway - I'm betting 2 or 3 will fix your issue. Good luck.
>
> regards
> L
>
>
Do I need a computer scientist degree to understand all this a normal user ?
I take my car to get fixed, I do not study mechanical engineering to do it.
Flameoff now please Johnny ;-)

-- 
Hilton Gibson
Systems Administrator
JS Gericke Library Room 1025D
Stellenbosch University
Private Bag X5036
Stellenbosch
7599
South Africa

Tel: +27 21 808 4100 | Cell: +27 84 646 4758




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