I have just installed Debian v7 network install.

There was an error using the network card and it asked for file
rtl-nic/rt1818f-1.fw
I downloaded
firmware-realtek_0.36+wheezy.1_all.deb and put it on a usb drive, the installation then continued (but I don't know if it used the file).

The installation then could not set up dhcp.

Now I have an installation and no network connection.
(I have various OSs on the same PC, different partitions, including Mint 15 and ubuntu server, all of which had no problems connecting to the internet.

The file /etc/network/interfaces is

auto lo
iface lo inet loopback

Nothing else (other than initial comment lines).

What do I do now?

You have no interface configured, probably you can try NetworkManager

I am logged in as root and when I try
network-manager
I get command not found.

If the device isn't configured automatically the firmware probably didn't install correctly.

This will help: https://wiki.debian.org/rtl819x

You may need to figure out if your chip is supported. A lspci or lsusb should show what chip you are using.

1 members found this post helpful.

1 members found this post helpful.

Debian doesnt include non free firmware with its Distribution others do thats why they installed fine.

get the firmware tar ball or deb and extract the contents to your usb stick and pop it in. if you get dhcp and see eth0 its working if not keep trying

1 members found this post helpful.

I tried the DVD version using the deb file which included the missing file. All is ok now, I have internet access - thank you for your comments.

so please mark the thread solved and also press YES if you really want to say thanks

I will mark it as solved (in that I eventually got Debian installed) but installing from the network version I did not solve.