Let us forget the past. And remember that the past is a gift of the present, not a substitute for the future.

I was trying to download the Debian testing DVD ISO and it looked like it would take a while, many hours and I wanted to power off the machine.  This was back a while ago with slower internet but, this topic is still relevant. Normally I use the torrent for the distro file, but on the testing branch of Debian, none were available.

The solution

I have a Raspberry Pi, it’s running 24/7, let it do the work overnight and I can just power down my machine and not worry about the download.
Instead of downloading the file itself, I grabbed the link to the download location.
Then executed

wget -c https://gensho.ftp.acc.umu.se/cdimage/buster_di_alpha2/amd64/iso-dvd/debian-buster-DI-alpha2-amd64-DVD-1.iso

Output...
 --2018-02-07 18:15:27-- https://gensho.ftp.acc.umu.se/cdimage/buster_di_alpha2/amd64/iso-dvd/debian-buster-DI-alpha2-amd64-DVD-1.iso
 Resolving gensho.ftp.acc.umu.se (gensho.ftp.acc.umu.se)... 194.71.11.176, 2001:6b0:19::176
 Connecting to gensho.ftp.acc.umu.se (gensho.ftp.acc.umu.se)|194.71.11.176|:443... connected.
 HTTP request sent, awaiting response... 200 OK
 Length: 3864182784 (3.6G) [application/x-iso9660-image]
 Saving to: `debian-buster-DI-alpha2-amd64-DVD-1.iso'

Suceess!

Now all I have to do is put the task in the background via Ctrl-Z and then bg and I detach from SSH’ing into the R-Pi and it will just download in the background to the harddrive tethered to it’s USB port. When you enter bg it will still print it’s progress to the screen, but the terminal can be closed out fine.
There is a -b option for wget that will launch it, into the background from the start as well.

ps aux|grep wget

…will confirm that it is running still…

 erick 12438 7.0 2.2 13120 10996 ? S 18:15 2:46 wget -c https://gensho.ftp.acc.umu.se/cdimage/buster_di_alpha2/amd64/iso-dvd/debian-buster-DI-alpha2-amd64-DVD-1.iso

Watch

While in the directory that it is downloading a watch command can be used to see the progress of the download…

watch ls -l debian-buster-DI-alpha2-amd64-DVD-1.iso

Output…

Every 2.0s: ls -l debian-buster-DI-alpha2-amd64-DVD... Wed Feb 7 18:56:25 2018

-rw-r--r-- 1 erick erick 280608768 Feb 7 18:56 debian-buster-DI-alpha2-amd64-DV
 D-1.iso

This will show a progressive increase in file size, in case you want to monitor it.