how do web hosting companies give ssh and root to so many users.

Abhishek Dixit abhidixit87 at
Sat Mar 5 13:24:42 UTC 2011

So if some one has to host 100 million websites and if 10 million asks
then the web hosting company has these 10 million IP addresses?
If yes who gives them so many IP addresses?
I may sound stupid but I read that IPv4 have finished.A long long time
back (approx 10 years back) I had asked one of my friend to install
Apache at his home computer and from a geographically distant location
I was able to see his thing as http://<Ip of my friend>
and things were working.

But I do not see the same thing these days if I have an ADSL router or
DSL line then I am not having any clue as why am I unreachable with
same way given that ISP  did not blocked any thing.So I believe the
ISP might be giving some sort of abstraction for such things.If that
being the case how does it work for a web hosting company and where do
they buy these IPs from and how much they pay for it?

On Sat, Mar 5, 2011 at 6:38 PM, Douglas Stanley
<douglas.m.stanley at> wrote:
> Simple. The hosting companies giving out root access have either many
> dedicated machines, each with their own public ip or they use
> virtualization.
> No magic, nothing special. Hosting companies just have that many ips to give
> out. For example, I rent rack space at a hosting company for my server, and.
> I have 16 ip addresses for it.
> You have to have dedicated public ips for things like https.
> As far as how they manage so many machines, if the customer has root, the
> customer is responsible for managing the machine. The hosting company
> probably just uses disk imaging or installation automation to quickly
> provision a new server, then the customer takes it from there.
> Again, no magic. Well automation stuff like cobbler and puppet may seem
> magical but, it's all stuff you could do yourself.
> Doug
> On Mar 5, 2011 7:06 AM, "Abhishek Dixit" <abhidixit87 at> wrote:
>> Hi,
>> it may not be the right list for this question so please consider my
>> apologies for that.The reason I am posting here is I feel the people
>> on Ubuntu server list are quite knowledgeable and will be able to
>> answer my question.I have been trying to understand this from quite
>> some time LQ,Serverfault, and many other forums I asked this question
>> but I am not satisfied with the answers that I got so asking here.I
>> want to know how do these web hosting companies give the end user (who
>> is their customer) the root access to the server.Where do so many IPs
>> come from and how is it possible that each customer who is given a
>> root access is able to gain root access.If I were to do the same let
>> us take a situation I have a public IP and a big server farm behind
>> that.
>> So if I have to give people from internet SSH access to those machines
>> behind my public IP in my server farm
>> then on the main machine in its .ssh/config I will configure a Proxy such
>> as
>> ProxyCommand ssh a nc -w 3 %h %p
>> So that I give the end user in one step a console to an internal
>> machine.That is one mechanism which comes to my mind or create some
>> sort of tunnel and then give a GUI to that SSH tunnel.
>> But what I have seen people doing is
>> ssh user@<IP given by hosting company>
>> and they directly login at port 22 and no tunnel or ProxyCommand (in
>> my opinion) is used there.
>> I don't think that above sort of Proxy configuration is used in such
>> scenarios.But the curiosity I have is how come these Web Hosting
>> Companies have so many public IPs and even if they have then how do
>> they actually manage root logins to each of these machines.Maintenance
>> of such a system would be extremely complex in my opinion.
>> Also no one seems to be using Apache Reverse proxy at the Hosting
>> level so how do these companies actually make this possible,
>> I am looking from a technical perspective.I am an experienced sys
>> admin kind of guy who knows Linux but never worked with a Hosting
>> Company.
>> Any link to some good doc which can satisfy my curiosity will be
>> greatly appreciated.
>> --
>> Regards
>> Abhi
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>> ubuntu-server at
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