How to share HDD on network
I am running Ubuntu 11 on one machine with 3 external drives. I wish to share these drives on the network, but am lost in Ubuntu, any help would be great!
Kinda depends on what clients you intend to share with.
If other Linux/*nix boxes, use NFS (Network File System). It's part of the kernel, works well, retains permissions and IDs quite nicely. Set it up in /etc/exports.
If other MS boxes, use SAMBA. There are several ways to configure Samba. GUI wise, SWAT being one of the more popular. But, if you learn your way around, it can be nicely configured using only a text editor. Google is your friend here. Try "Samba configure GUI" as a starter.
And, of course - on a mixed client LAN - you can use both at the same time. But, you can run into "issues" with concurrent access.
It also depends what you mean by "share." File sharing? Volume sharing?
Most use a SAN for this, with client software that permits sharing and locking as required for the application.
If all you want to do is "add storage," then NAS works fine and is a lot easier.
I'd imagine that if you are just using those three drives as "storage dumps" for other computers on the LAN in a mixed OS environment, samba is what you'd want. Linux, Windows and Mac are all able to talk to a samba share.
The drawback for samba is that security is based on being "allowed to connect to the share", and the individual files in the share basically belong to everyone who has a password for that share. This is probably fine if you are just going to dump all your music and movies onto those drives so that you can have them available at any computer or media player on the LAN. This is not a good situation if you are installing program/executable files to those drives, though, since a virus on one computer can be spread to every computer that is attached to that share if you are running programs installed on those drives.
You can set up a samba share in seconds in Ubuntu using the file browser Nautilus. Just right-click on a folder and click on "Sharing Options" and go from there. If you want to have a bit more control over the sharing process, you should probably use a samba share GUI as KA70 suggested above.
NFS is great in a *nix environment, and even better if you know what you are doing. I have never used NFS, always opting for either samba or iSCSI, so I can't give you any real help here.
iSCSI is a fun option, but only if you want to allow only one computer to use the drive at a time. It's really only useful to SAN administrators with diskless systems or virtual machines and is more than likely not what you are looking for.
There are several open source projects that allow you to set aside a computer to be used solely as a fileserver, or NAS (Network-Attached Storage). I doubt you're trying to go all the way like this, but a NAS makes some things a whole lot easier, such as automated backups. FreeNAS is an operating system based on FreeBSD that turns a computer into a NAS and gives you an easy GUI to manage disks, volumes, and snapshots. It uses a pretty advanced filesystem, ZFS, and does some really impressive RAID stuff in the background. It would be perfect if you had a bunch of hard drives and a computer you don't need for anything else.
Anyway, after all that silly extra junk, my guess is that you're looking for samba, so if you just Google "samba setup", and throw "GUI" or "configuration" in there for more information, you should get everything you need.