0

I read this answer about how to apt install from a specific source. https://askubuntu.com/questions/27362/how-to-only-install-updates-from-a-specific-repository/57749#57749

But I feel confused with this example.

source is: deb http://mozilla.debian.net/ squeeze-backports iceweasel-release

command is: apt-get install -t squeeze-backports iceweasel

So it is what after deb http://xxx.xxx.xx/ that uniquely define a source.

Then I checked my source list. I found duplicated paths and wonder how does apt distinguish one from another?

Hit:1 http://mirrors.aliyun.com/ubuntu bionic InRelease
Hit:2 http://mirrors.aliyun.com/ubuntu bionic-security InRelease                                                       
Hit:3 http://mirrors.aliyun.com/ubuntu bionic-updates InRelease                                                                                     
Hit:4 http://mirrors.aliyun.com/ubuntu bionic-proposed InRelease                                                                                    
Hit:5 http://mirrors.aliyun.com/ubuntu bionic-backports InRelease                                                                                   
Ign:6 http://dl.google.com/linux/chrome/deb stable InRelease                                                                                             
Hit:7 http://packages.microsoft.com/repos/vscode stable InRelease                                                                                        
Hit:8 http://dl.google.com/linux/chrome/deb stable Release                                                                                               
Ign:10 https://dl.bintray.com/rabbitmq-erlang/debian {distribution} InRelease                                                                            
Err:11 https://dl.bintray.com/rabbitmq-erlang/debian {distribution} Release                                                                              
  404  Not Found [IP: 52.41.180.114 443]
Hit:12 http://ppa.launchpad.net/certbot/certbot/ubuntu bionic InRelease                                                                                  
Hit:13 http://linux.teamviewer.com/deb stable InRelease                                                                                                  
Hit:14 https://www.charlesproxy.com/packages/apt charles-proxy InRelease                                                                                 
Hit:15 http://ppa.launchpad.net/fontforge/fontforge/ubuntu bionic InRelease                                                                              
Hit:16 https://download.sublimetext.com apt/stable/ InRelease                                                              
Hit:18 http://ppa.launchpad.net/nathan-renniewaldock/flux/ubuntu bionic InRelease                                          
Hit:17 https://packagecloud.io/rabbitmq/rabbitmq-server/ubuntu bionic InRelease

For exmaple:

 Hit:17 https://packagecloud.io/rabbitmq/rabbitmq-server/ubuntu bionic InRelease
 Hit:1 http://mirrors.aliyun.com/ubuntu bionic InRelease
 Hit:12 http://ppa.launchpad.net/certbot/certbot/ubuntu bionic InRelease  
 Hit:1 http://mirrors.aliyun.com/ubuntu bionic InRelease

All the 4 source links have ubuntu bionic InRelease.

How would apt know which specific source I want to install from, if simply provided

apt install something_all_these_4_source_has -t ubuntu bionic InRelease, without the full url ?

(Assume that all 4 sources has the application I want to install, but with different version)

1

So it is what after deb http://xxx.xxx.xx/ that uniquely define a source.

No, a source is defined by its Release file, and the entries there, in particular the Codename entry; see for example the Stretch backports Release file.

When you specify the -t option, that overrides apt’s “default release”, which is the highest-priority release. The possible values are the accessible releases, based on the configured repositories. “ubuntu bionic InRelease” isn’t a valid target.

If multiple repositories with the same name have different versions of a given package, apt’s priority-based resolution determines which version is used; see APT Pinning dependencies resolution (this allows you to distinguish between package origins, i.e. the repository containing them). By default, the highest version wins. You can override that by specifying a specific version (rather than repository or target release) with =: apt install package=version.

There is a fundamental assumption underlying all this: all available copies of a given version of a package are identical, across all repositories advertising it.

2
  • I noticed that my observation is totally wrong. squeeze-backports iceweasel != squeeze-backports iceweasel-release. Anyway, I successfully installed newer version fo erlang with the rabbitMQ installation guide. – Rick Mar 25 '20 at 15:05
  • I checked the release file you provided and opened several source urls to examine some directory strcutures. I found it hard to connect these things together in my mind. Source url format, Source url directory structures, Codename, blablabla and how these things are related to the argument after -t. Complicated stuff but I am still curious. Some elementary materials (videos, webpages) are much appreciated, if you have spare time :P. – Rick Mar 25 '20 at 15:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.