Remote and Network Computing
Users have been accessing sites remotely since the earliest days of the network.
telnet and ftp (and their secure successors)
These two commands and their secure successors
have been for decades
fundamental commands of the Internet / remote computing.
- Login to remote host
- Transfer files to/from remote host
With telnet you get a command-line,
with ftp you get a read-write file system.
- telnet, 1971
- ftp, 1971.
These two commands have been replaced by secure versions:
(both use ssh)
In the past: ftp of public data
Read-only ftp (File Transfer Protocol)
was what people used to publish files and archives online
before the Web
(http - Hypertext Transfer Protocol).
This is rarely used any more.
Though most browsers should be able
to read public files through it.
Now the main use: ftp of private data
(Secure) ftp is now far more often used in read-write mode
for remote private data (needs password).
e.g. Your web hosting company uses a Unix server.
periodically upload your web site (edited in Windows)
with a private ftp.
There are many graphical drag-and-drop ftp clients,
and even programs that
make the site into a full Windows drive.
ssh and sftp to:
(on a CA subnet)
How to login to Linux at DCU
Windows GUI, Unix ssh, Unix file system
I can use the following two to run a Windows GUI with a Unix ssh command-line underneath.
My files on the remote Unix server
appear as just another read-write Windows drive.
I can use Windows apps to edit them.
And I have a Unix ssh command-line always open
on which I can run scripts to process them:
you can make your local Unix machine
look like a drive in Windows.
So you can access and edit all your Unix files using
you can make a remote Unix machine
look like a drive in Windows.
This strategy uses ftp in the background to read-write remote files.
The remote Unix files
look just like a drive.
All programs are Internet-enabled.
Alternatives to WebDrive:
- remote site appears as drive or directory on normal file system
Map Network Drive
(built-in to Windows).
Q. Can this map remote sftp server to a regular drive letter?
- See also:
Unix GUI, visible remotely
Run Unix GUI program on remote Unix machine:
Run Unix GUI program on remote Windows machine:
FTP (sftp / scp / ftps) scripting is a good/essential tool for website maintenance.
Say you are working on an offline copy of a website of 10,000 files.
You make changes to 137 files among the 10,000.
You want to upload the 137 new files, but not the entire 10,000.
Drag and drop the 137 to their correct destinations could be quite tedious.
For repetitive tasks, drag-and-drop is not
a better interface than being able to write automated scripts
(this will be a theme of this course).
You can write ftp scripts ("macros") and call them from Shell scripts:
Sample ftp scripting
This is how I work:
To make a new build of my (huge) genealogy site:
I just want to upload the small number of files that have changed since the last build.
I run a program to build an ftp script with all the changes, like the ftp script below.
I then run
with this ftp script.
put ./Flanagan/NMI.bird/IMAG1024.jpg ./Flanagan/NMI.bird/IMAG1024.jpg
put ./Flanagan/NMI.bird/IMAG1025.jpg ./Flanagan/NMI.bird/IMAG1025.jpg
put ./Flanagan/the.bird.html ./Flanagan/the.bird.html
put blog.html blog.html
Changes directory on remote site.
Changes directory on local site.
Makes remote directories.
Puts various files into various destinations.
The above ftp script is automatically built by a program.
- See also tools like
You can also do HTTP GET or POST scripting from the
Some tools that do this:
- dumps to command line by default
- -s for silent mode
- does HTTP GET
- does HTTP POST
Idea: Your files are "on the network" ("in the cloud") somewhere.
You can access them and make changes to them
All copies stay in synch.
This is what you actually have within DCU
(can move from terminal to terminal,
accessing files at central server).
Various ways of working:
- 1 copy of files.
Copy is on server.
Read files from server when we need them,
and copy any changed files back to server over the network, as you go along.
2 copies of files.
Work on local machine which has synchronised mirror of server files.
Have to keep copies fully in synch over the network.
- Physically bring hardware to and from work
(laptop or USB key or external hard disk).