(Side note: This is based loosely on a previous tutorial about getting PCLinuxOS, which was lacking some important detail and needed to be adapted to more general purposes. This is the improved result.)
One very common operation in the GNU/Linux world is downloading of the ISO (CD or DVD image) for a given GNU/Linux distribution. Typically, this is around 650 or 700 MB – a sizable download. One of the biggest wastes of bandwidth – not to mention your time and patience – happens when an ISO download (or any other large download, for that matter) is interrupted or mysteriously quits… especially if it occurs when your download was almost complete. If you’re not using a download manager, you’re stuck downloading it all over again from the beginning.
There are a number of graphical download managers available at no cost. Ease of use varies, and importantly, so does freedom of use. That is, some of them are free/libre (also known as open source) software and some are not. The free/libre applications are safer security-wise to use on your system, since their source code is available for the public to scrutinize and ensure that they don’t do anything they shouldn’t be (such as collecting your information and sending it to someone without your knowledge or permission.) But the simplest one of all, in my opinion, is wget from the GNU Project, a well-trusted organization dedicated to producing and promoting free/libre software. It is safe and also very simple to use, even for those who are scared of the command prompt. There are no unnecessary frills, nag screens, advertisements, registration forms, restrictions, or user agreements in legalese. It comes with your GNU/Linux distribution and is almost always installed by default. That makes it very convenient to use.
First, use your web browser to navigate to the download page for the distribution you want to download. Find the link to the ISO you want. Right click the link and (assuming you’re using Firefox or Iceweasel) click “Copy Link Location”.
Now you’ll need to open a command prompt. Its location in your menu varies depending on which distribution you’re using. Look for an icon that looks like a little black computer screen. It may be called “Terminal”, “Console”, “Konsole”, or “Command prompt.” Click it and you should have a window with a command prompt that looks something like this:
At the prompt, type “wget -c” (without the quotes) followed by a space. The -c option tells wget to Continue getting any partially-downloaded file. If the download is interrupted or fails for some reason, you can repeat the same command and it will pick up where it left off. Now paste in the URL of the ISO by holding down the <shift> key and tapping <insert>.
The command you typed in will look something like this:
wget -c http://somewebsite
Here’s an example:
Hit <enter> and it will download the ISO to whatever directory you’re in. It will also display some information about your connection, size of the file, percentage downloaded, a simple progress bar, and estimated time until the download is complete. And here you thought you’d have to give up all those nice features just because you’re using the command line! Those GNU guys and gals are pretty smart.
g33kgrrl@home:~$ wget -c http://mirror.csclub.uwaterloo.ca/ubuntu-releases/jaunty/ubuntu-9.04-desktop-i386.iso
--2009-10-03 21:27:04-- http://mirror.csclub.uwaterloo.ca/ubuntu-releases/jaunty/ubuntu-9.04-desktop-i386.iso
Resolving mirror.csclub.uwaterloo.ca... 22.214.171.124
Connecting to mirror.csclub.uwaterloo.ca|126.96.36.199|:80... connected.
HTTP request sent, awaiting response... 206 Partial Content
Length: 732909568 (699M), 731590789 (698M) remaining [application/x-iso9660-image]
Saving to: `ubuntu-9.04-desktop-i386.iso'
1% [ ] 9,456,127 222K/s eta 50m 22s
When it’s done downloading, you’ll get a message something like this:
[ |||||||||||||||||||||||||||||||| ] 732,909,568 51.9K/s in 48m 32s
2009-10-03 22:15:36 (51.9 KB/s) - `ubuntu-9.04-desktop-i386.iso' saved 
You might not want to close the terminal window just yet. The ISO file will be saved in the directory your terminal is currently pointed to. Most often this is your home directory (/home/yourusername), which you can access by clicking your Home icon on the desktop or in your menu. If you want to be sure, type “pwd” without the quotes (for “Present Working Directory”) and it will tell you where you are:
In this case I can just click my Home icon and then look for the ISO in that folder.
Don’t forget to use checksums to verify that the ISO downloaded correctly and that the CD burned properly! It’s worth the headaches it saves. I have a tutorial on it here.