From where does ubuntu install programs when we run sudo apt-get command

Question

when we run the command in the terminal for downloading and installing a program from where ubuntu downloads the program for example i want to install ithor on my pc i should run command

$ sudo apt-get install lthor

now from where this package is downloaded and installed and if possible can someone provide me the direct download link for Ithor as my internet connection is very slow and cant download it directly so need an offline installer

also i would like to know if i have downloaded a tar.gz file for installing firefox how to install it now.

Answer 1

Those are pulled from the package repositories listed in /etc/apt/sources.list.

If you want to download a specific package without actually installing it, the -d option to apt-get will leave you with a standalone .deb package you can later install with dpkg -i.

Answer 2

you can find the sources in:

/etc/apt/sources.list

for installing source packages you can refer to the 'installing' text files within the tar.gz file. most commonly used is:

./configure
make
sudo make install