How to fix hash sum mismatch and size mismatch errors from apt-get / apt-cacher
BY webmaster
12 years ago
7 comments comment
We run apt-cacher to save bandwidth in our intranet. All Ubuntu systems in our office uses the apt-cacher server to update and upgrade. Recently we started getting the hash sum mismatch and size mismatch errors. After some dabbling with the settings and the files we figured out a simple solution for this problem. Whenever we were running apt-get update, apt-get upgrade or apt-get dist-upgrade we were getting these annoying show-stoppers. The exact errors we were receiving were of this form
W: Failed to fetch Hash Sum mismatch
W: Failed to fetch Size mismatch

Once we started getting this error for a package in one of the machines in the network, it reoccurred for the same packet on all the other machines in the network. So we figured that it had something to do with the apt-cacher and we forced a reload of the specific package by going to the apt-cacher repository(we have it at the default location - /var/cache/apt-cacher) and deleting the file with the name for which the error was triggered from within the var/cache/apt-cacher/private folder. This file is a flag which is used to indicate the download status of the specific package.

While doing research on this problem we also realized that a possible solution was to change the repository server to some other server than the one already setup, either manually by editing the sources.list file or by changing it from synaptic package manager. This was how we initially solved the problem to get going but we have a lot of systems and we had only limited bandwidth and we had to save the bandwidth.

We also realized that we started getting this problem once we setup the apt-cacher with expiry-time of 24 hours. It could possibly have been that the packages were updated in between and our cache had gotten stale. So a similar issue could happen when people use proxies or apt-on-cds for updating packages. Once we fixed the errors we set the expiry-time to 0 which meant that new packages.gz files are downloaded every time someone requested for an update/upgrade. Hope this helps.

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on 04th April 2007 / by webmaster
Linux is the epitome of the FLOSS model. Technical Solution Linux installation Leave a reply Your email address will not be published. Required fields are marked * Dewey J. Corl (not verified) access_time 10 Aug 2020 - 23:51 Linux is not ready for the general public! (I am a Ubuntu user). For proof, 1. try to simply print labels on a Dymo label printer. It takes a LOT of work to get to the ease of label printing already available in Windows and Mac. 2. try syncing a modern Palm based PDA. Yes, jpilot and others will sync the main data, but pictures and midi files do not get transferred without a lot of extra setup. These are examples of applications that are not ready for the general public. Since an operating system only supports applications, Linux is not ready to be a common desktop for the general public. While we are waiting for the applications to catch up, keep up the good work!! Anoop John (not verified) access_time 10 Aug 2020 - 23:51 Dewey Yes you may be right. But these are not applications that a common man would use. A common man would use one of these applications - Internet browser, Chat Client, Email Client, Document Writer, Presentation Creator, Spreadsheet Editor, Movie Viewer, Music Player, CD/DVD Writer. Both examples you cited are more specific applications that only a small percentage of the whole population uses. It will take time before those hardware vendors identify the need from their perspective to address the Linux community. Krishnadas (not verified) access_time 10 Aug 2020 - 23:51 Dear Mr Anoop, Thank you very much for the free installation of LINUX done in my PC. I am getting immersed in the LINUX and seeing the versatility. To my surprise, I am able to read one of my old backup CD(wherein lot of my valuable file exist) done in DIRECT CD wizard (a custom cd writing software of Easy Cd creator in WIN98) which could not be read in XP. Installation of old version of easycd creator/direct cd program was not possible in XP. I thought that possible i lost all data. Very pleasant start! Srikanth N. S. (not verified) access_time 10 Aug 2020 - 23:51 Hi Anoop, My friend is thrilled with Ubuntu. One of his grouses with windows was that after OS installation, everything else is to be installed separately which is a real headache. WHereas if u install Linux, everything is installed as a package and he is thrilled to bits! Let linux installation spread in Trivandrum and your service in this direction is highly appreciated. Kepp up the good work Regards. PDA Freak (not verified) access_time 10 Aug 2020 - 23:51 Is it possible to install linux on a packardbell notebook ? Pagination Current page 1 Page 2 Next page Next › Last page Last » Add new comment
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Atomymous (not verified)
access_time 10 Aug 2020 - 23:51

I found this article because I was experiencing the same problem.

My case turned out to be because, here at work, I'm behind the corporate firewall and needed to configure apt-get to use the proxy server (in Synaptic Package Manager -> Settings -> Network tab)


i am running ubuntu 8 at home, desktop.
i keep getting fetch fail, hash sum mismatch from updates.
do you think the above fix will work and if so could you generate a step by step walkthrough as i am new to linux and command line use.

Nigel Horne (not verified)
access_time 10 Aug 2020 - 23:51

You also need to check if you're running Dans Guardian. That software stops you updating your system.

sadeed86 (not verified)
access_time 10 Aug 2020 - 23:51

try updating any package using the same source..for example, if u r using lock info which is downloaded from insanelyi, adding more plug in such as weather plug in must be from the same source from insanelyi as well...the same apps from different source has different packages, thats why updating or plugging in show some error...