[ubuntu-uk] value of /var/cache/apt/archives ?

[alan c]

I have just discovered that /var/cache/apt/archives seems to contain 
all the installed updates  since original install. Is this a correct 
belief please?

I do not want to clear this, not just now, anyway - I am very 
interested in using this archive to create a CD from time to time in 
order to allow me to install and update PCs of several friends who 
have only a very slow dialup internet connection. If I can do this it 
will be important for me (and them).

Thoughts rushing on - I guess that if they have apps installed which I 
do not have, the relevant updates will not be found on my machine (?) 
If so this is a minor issue for me.

Am I on the right lines here?
-- 
alan cocks
Kubuntu user#10391