Re: Beginner lost with Ubuntu
It is important to note the philosophical differences between Linux and Windows. Linux is modular whereas Windows is monolithic. In practical terms and especially as it applies to you, this means that you must specifically add functionality in Linux whereas Windows will have more functions included by default. Users from Windows often consider this a Linux shortcoming until they start dealing with security: the modular nature of Linux enables it to load only such modules and services as are needed for specific tasks which means that there are almost no holes for malware to exploit. In contrast, the monolithic nature of Windows is a large part of why it blows chunks security-wise. However, this fine granularity of control in Linux (and by extension Ubuntu) does make it more complicated.
In your case, you cannot get your external disk visible across the network because:
1. External disks are removable and therefore assumed to be impermanent, like CDs, DVDs etc. It used to be that the default behaviour for such drives was to restrict them to local access only, which is not only reasonable, but a highly logical default. After all, if such disks are readily shareable across a network, what happens to the poor sod who has files open on your external drive should you decide to unplug it? I believe that the newer distros now allow such sharing, although I haven't experimented with this for years.
2. Linux desktop distros (of which Ubuntu is an example) are generally set up to act as clients only and not as servers. This is the reason why you hear some people (mistakenly) telling you that a firewall is superfluous because the default Ubuntu install has "no ports open". Since the default desktop install does not include server capabilities, it indeed opens no ports to the outside world and is far more secure than Windows because of this. However, this also means that it won't automatically share files with another computer because it doesn't have the required server software. If you want to share files from your box, you will have to install server software (Samba or NFS) and expand its role beyond that of a desktop so that it becomes a server. This will open security holes, and you should take care to guard these holes and harden your box properly. BTW, you should still activate Ubuntu's firewall. It's good security practice to have it running even if all ports are closed by default. It's very easy to download GUFW from the repositories and simply turn it on.
3. The HP 4L is an ancient warhorse and does not have the circuitry needed to be automatically recognized by Avahi or Bonjour. Please specify what you meant by network? It only has a 36 pin Centronics interface, so is it hooked up directly to your computer (and you want to share it with others)? Or did you install a network card? Or is it connected to a HP printer server? Please clarify. At any rate, it too will require a few more steps to set up.
Re: turning your box into a server.
Make no mistake... this is what you are trying to do the moment you want to "share files across a network". If you are sharing with other Windows boxes, then the best method is to install Samba. You might observe that your box already has some Samba software running. However, this is only client-side--that is, it only allows you to see Windows shares, not export them. If you want to install Samba server, there are many guides on the internet, but this is an easy one to follow.
Once installed and configured, you need to use nautilus to allow (set permissions) those specific directories that you want to share. Think twice about sharing external drives. If you physically unplug one while files are open, not only do you hose the work of the connected user, but you will usually corrupt the file structure of your external drive and may cause a kernel panic in the remote users' computers as well. External drives really aren't meant to be shared this way.
As sudodus suggests, should deal with your printer issue on a separate thread. If you post, be sure to provide missing details as asked in question 3 above.
Newb: How far must I jump to clear the ledge halfway down?
Guru: It's bad to jump off cliffs. Let's look at better options.
Newb: Stop harping about "best practices" and just tell me.