~~NOTOC~~ /*{{page>livereload&nodate&noeditbtn&nofooter}}*/ {{page>css&nodate&noeditbtn&nofooter}} ===== Week 11 — Mobility of data and computation ===== This week's topic is about mobility: moving your data, and your computation, around the Internet. /* Data mobility * file transfer with sftp/scp * file sharing * cloud concepts Computation mobility * The network is the computer. * Remote login with secure shell. * Client/server architecture for graphical displays; X11; remote desktop protocol; VNC. Deliverable * download a text file from a server, modify and edit it * using command-line tools, upload the result */ ==== Evaluation ==== Up to 10 points can be gained towards your final score by completing the **in-class exercises** on Friday. ==== What you will learn from this class ==== * What the File Transfer Protocol is. * How to transfer files to/from a remote server. * How to view the contents of a remote server using a web browser. * How to set up a FTP server on your Windows computer. * How to connect to a command line on a remote machine using secure shell. * How to copy files to/from a remote machine securely using secure copy. * How to synchronise two directories or files using ''rsync''. * What remote desktops are. * How to use VNC to connect to a remote desktop. ==== Preparation ==== This week's preparation is to watch some short videos about Internet services that help with mobility of data and computation. | What is FTP? | https://m.youtube.com/watch?v=wig1szO7en8 | | Transfer Files via FTP on Windows | https://m.youtube.com/watch?v=58I2YoKJ3dc | | Using SSH and SCP | https://m.youtube.com/watch?v=rm6pewTcSro | | How to make backups using ''rsync'' | https://m.youtube.com/watch?v=8d5B1JC-1d4 | | How to use TightVNC | https://www.youtube.com/watch?v=x9xTyh63Tos | | ::: | https://www.youtube.com/watch?v=98rQ9J5XE_g \_\_ (Japanese) | ==== Notes ==== === FTP: file transfer protocol === **What is FTP?** \_\_\_\_ [[https://m.youtube.com/watch?v=wig1szO7en8]] Summary: * File Transfer Protocol (FTP) uses TCP as its underlying transport protocol. * FTP allows files or data to be transferred between any two computers on the Internet. * Because it uses TCP, all transfers are reliable. * FTP uses a "client-server" model: the remote computer (server) stores the files, and your computer (client) transfers files to or from the server. * When connecting to the server, the client user (you) must first authenticate (log in). * If the connection is accepted, the client (you) can send commands to list directories, upload (send) or download (receive) files, and so on. * You can interact with FTP using a graphical client, which looks a bit like the Windows Explorer or Mac Finder. * You can also interact with FTP using a command-line interface typing actual FTP commands yourself, which is much more flexible. * FTP is useful for large file transfers or bulk uploads that are impossible with e-mail or online file sharing services. * FTP is fast and uses very few resources on the server. * FTP is often used by web site hosting services (Wix, GoDaddy, Weebly, etc.) for users to upload their web site content. == Useful FTP client commands == | ''ls'' | \_ -- list the current directory | | ''cd //dirname//'' | \_ -- change the current directory | | ''bin'' | \_ -- change to binary mode (ensures perfect copies of files) | | ''get //filename//'' | \_ -- download (receive) files | | ''put //filename//'' | \_ -- upload (send) files | | ''bye'' | \_ -- terminate session (log out) | == Exercise: practice using FTP on a public test server == {{11-ftp-public-ann.png?direct}} You can practice FTP using a public server providied by ''speedtest.tele2.net''. The example shown here uses the Windows FTP client, but it will work the same on Mac or Linux. The parts typed by the user are shown with a red background. (Click on the image to see it at the original size.) - Connect to the server using this command: ''ftp: speedtest.tele2.net'' - When asked, enter the user name: ''anonymous'' - When asked for a password, press ''Enter'' (to leave the password blank). - Use ''ls'' or ''dir'' to obtain a listing of the public FTP directory. - Make sure you are transferring files in binary mode with this command: ''bin'' - Download a test file using this command: ''get 10MB.zip'' - Close the session with this command: ''bye'' (Note that these zip files contain junk and there is nothing you can recover from them.) == Exercise: view an FTP server using your web browser == Most web browsers can connect to and view FTP sites. - Visiting this URL in a browser tab or window: ''ftp://speedtest.tele2.net/'' - Try clicking on the ''upload'' directory to enter it. - Leave the window open while you complete the next exercise. == Exercise: practice uploading a file to an FTP server == - Create a small text file called ''test.txt'' containing a few words of text. - Connect to ''speedtest.tele2.net'' using your command-line FTP client, as shown above. - Once connected, use the ''cd upload'' command to change to that directory. - Use the ''bin'' command to change to binary mode. - Use the ''put test.txt'' command to send your text file to the server. - Refresh your browser window; you should see your file on their server. - Click on ''test.txt'' in your browser, download the file, and verify it has your few words of text inside it. ++++ Exercise: practice using FTP on your own Windows machine | If you are running Windows and would like to practice on your own machine, this video show you how. **Transfer Files via FTP:** \_\_\_\_ [[https://m.youtube.com/watch?v=58I2YoKJ3dc]] Summary: * Download a simple Windows FTP server: https://www.malavida.com/en/soft/baby-ftp-server/ * Unpack the downloaded zip file: - right-click on the zip file, - select "Extract all...", - leave "show extracted files" selected, - click "Extract". * In the extracted folder, run the "babyftp" application; by default the application communicates using port 21 (the standard port for the FTP service). * Click on the "settings" button, select the folder you want to share, and then enable permission for the activities you want to allow clients to perform. * Find the IPv4 address of your computer using ''ipconfig''; alternatively, you can use 127.0.0.1 if you want to connect from the same computer. * Using the same computer, or another computer //on the same network//, run an FTP client. * Windows has a built-in command-line client called ''ftp''. * Run it from a terminal window or from a Windows ''cmd'' window. * If you prefer a graphical interface, one option is Filezilla: https://filezilla-project.org/download.php * The video shows how to use Filezilla. * Here is how to use the Windows command-line FTP client: - Run ''cmd'' (or a terminal program). - Type ''ftp'' followed by the IPv4 address of where the FTP server (e.g., babtftp) is running. For example, on my network, I typed ''ftp 10.0.1.11'' (but you need to use the IPv4 address that ''ipconfig'' told you, which //will// be different to mine). - When logging in, use the username 'anonymous' and leave the password blank. ++++ === SSH: secure shell (remote login) and secure copy === **Using SSH and SCP:** \_\_\_\_ [[https://m.youtube.com/watch?v=rm6pewTcSro]] ''ssh'' is stands for secure shell. ''ssh'' is a way for you to remotely access a computer with full command line access. To connect to a remote machine, use ''ssh //username//@//address//'' where * //username// is your account on the remote machine and * //address// is the IP address or DNS name of the remote machine. The default port of ''ssh'' is 22, but for security reasons many administrators choose to run ''ssh'' on a different port. To change port that you are connecting to (e.g., port 1234) use the ''-p'' (port) option: ''ssh -p 1234 //username//@//address//'' Once connected, ''ssh'' will prompt you for your password on the remote machine. Type the password to authenticate and log in. If successful you will have full command-line access to the remote machine, just like running a terminal on that machine. One thing you can do remotely is to find the full path name for a file that you want to copy securely to your local machine using ''scp''. ''scp'' stands for secure copy. ''scp'' is a way to move files between computers that is more secure than FTP. It can copy individual files, multiple files using wildcards, or an entire directory (recursively). The syntax of ''scp'' is just like the ''cp'' command: ''scp //fromPath// //toPath//'' If you are copying a directory recursively, add the ''-r'' (resursive) option: ''scp -r //fromDirectoryPath// //toPath//'' In either case the //toPath// can be a filename (which is replaced if it exists) or a destination directory name. Either //fromPath// or //toPath// (but usually not both) can be a remote file. The syntax for a remote path is ''//username//@//address//://path//'' where * //username// is your account name on the remote machine, * //address// is the IP address or DNS name of the remote machine, and * //path// is the path to the remote file, either absolute or relative to your home directory on the remote machine. (Note that if you want to guarantee that //path// is the name of a directory then put a trailing ''/'' after it as shown in the examples below.) If the ''ssh'' port on the remote machine is not the default 22 then add the ''-P'' (port) option (note the //capital// letter). Assuming my remote username is ''piumarta'', the remote machine is called ''server'', and ''ssh'' is running on port 1234, then ; ''scp -P 1234 piumarta@server:/tmp/data.txt /tmp/'' : copies ''/tmp/data.txt'' from the remote machine ''server'' into the directory ''/tmp'' on the local machine ; ''scp -P 1234 /tmp/data.txt piumarta@server:data/'' : copies ''/tmp/data.txt'' from the local machine to the ''data'' directory located in my home directory on the remote machine ''server''. ; ''scp -P 1234 -r $HOME piumarta@server:/var/backups/laptop'' : copies my entire home directory recursively to ''/var/backups/laptop'' on the remote machine ''server''. The last example makes a backup of all your personal files. However, it is not an efficient way to back them up because it will copy every file --- even those that have not changed since the last backup. === Synchronise files/directories: rsync === The ''rsync'' command //synchronises// two files or directories. The files or directories can be local or remote. The syntax is the same as ''scp'' and the ''-r'' option (recursive) is used to copy directories. One popular use of ''rsync'' is to make backups of important files. Compared to ''scp'', the advantage of ''rsync'' is that only changed files are copied to the destination. The first time you make a backup using ''rsync'' can take a long time, but subsequent backups are much faster because they copy only the changes you made to your files. Even very large files are copied efficiently because only the changed parts are updated. **How to make backups using ''rsync'':** \_\_\_\_ [[https://m.youtube.com/watch?v=8d5B1JC-1d4]] === Remote desktop === {{11-vnc-rpi.png?direct}} A remote desktop gives access to the graphical user interface of a remote computer over the Internet. A user can interact with the remote system as if they were sitting in front of it. Keyboard and mouse inputs are transferred from the user's computer to the remote computer, and screen updates are transferred from the remote computer to the user's computer. Typical uses include using a workplace workstation when at home or vice versa, fixing a computer problem remotely, performing administrative tasks easily, and demonstrating processes or software applications. In addition, //headless// computers that have no monitor, keyboard, or mouse can easily be accessed remotely by administrators. Protocols for remote desktop connectivity include: ; Remote Desktop Protocol : RDP is built-in to Windows professional and higher versions. One disadvantage is that only one person can access the controlled computer at once. When a remote user connects to it, the local user is locked out. ; Virtual Network Computing \_\_ https://tightvnc.com/ : VNC is available on (and interoperates between) Windows, MacOS, and Linux. One advantage is that multiple users can connect to the same remote screen, and a user sitting at the remote computer is not locked out when remote users connect. /*https://tightvnc.com/doc/win/TightVNC_for_Windows-Installation_and_Getting_Started.pdf*/ **How to install VNC:** \_\_\_\_ https://turbofuture.com/computers/How-to-Install-and-Configure-TightVNC **How to use TightVNC:** \_\_\_\_ https://www.youtube.com/watch?v=x9xTyh63Tos **ネットワーク経由でWindows 10を操作する（VNC編）:** \_\_\_\_ https://www.youtube.com/watch?v=98rQ9J5XE_g /*[[https://thetechnologyteacher.wordpress.com/vncthumbnailviewer/]]*/ /* syllabus */ /* * Local Variables: * eval: (flyspell-mode) * eval: (ispell-change-dictionary "british") * eval: (flyspell-buffer) * End: */