Krdytkyu

Specific files are causing this error, like

Err:7 http://in.archive.ubuntu.com/ubuntu bionic/main i386 Packages 

Err:4 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages

I have tried all the solutions posted in similar questions, but it still seems to happen.

I've tried fixes from the following questions but still no luck:
sudo apt-get update failes due to Hash Sum mismatch

"hash sum mismatch" error when doing update

"apt-get update" always failed to fetch

Also I am behind a proxy, so I have added these lines to etc/apt/apt.conf

Acquire::http::proxy "http://<proxy>:<port>/";

Acquire::ftp::proxy "ftp://<proxy>:<port>/";

Acquire::https::proxy "https://<proxy>:<port>/";`

I have no good explanation for why this might work, but it just did for me, when I got these errors trying to do sudo apt install emacs25 or sudo apt-get install emacs25. So in case it works for others:

This install of emacs25/bionic,now 25.2+1-6 amd64 required several dependent packages, namely:

1. emacs25-bin-common/bionic,now 25.2+1-6 amd64


2. emacs25-common/bionic,bionic,now 25.2+1-6 all


3. emacs25-el/bionic,bionic,now 25.2+1-6 all


4. emacsen-common/bionic,bionic,now 2.0.8 all

I wanted to see if I could narrow down what the particular problem file was, since they were all throwing hash sum errors, so I tried to install emacs25-common. Same issue (though it had dependencies on all the other three numbered above).

Then I tried sudo apt install emacs25-el. This worked, and curiously, the first dependency it installed was emacs25-common — the one I'd just tried to install unsuccessfully. It installed emacs25-common and the other three packages (all except for emacs25 itself) successfully.

Then I did sudo apt install emacs25. This, too, worked.

So this is voodoo, but I would suggest trying to install the dependencies separately first, trying different dependencies, until one does install, and then trying again.

My guess would be that something server-side was being cached, and breaking the normal order of requests resulted in a cache miss allowing the original file to be re-checksummed, but that's a total stab in the dark.

(After the above was done I was able to install the suggested package using sudo apt install emacs25-common-non-dfsg without issues.)