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Go into CA labs Overview - Remote access termcast

ssh ssh with keys sftp

Use your own Linux

How to login to Linux at DCU

There are many different ways to use Linux at DCU.

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Go into CA labs

1. Go physically into CA labs.
2. Reboot a PC.
3. Choose Linux.

4. The School of Computing ("CA") has its own Linux and Windows sysadmins.
5. For Linux admin problems (e.g. password issues) see docs:
   • docs.computing.dcu.ie
   • FAQ

   And can email sysadmins at:

    support@computing.dcu.ie 

Overview - Remote access to DCU Linux

Access from home and from Windows.

1. ssh
   • This is a hugely important protocol, in use globally to give you a command-line on a remote Linux/Unix system. More below.

2. sftp
   • This is a hugely important protocol, in use globally to give you a read-write file system on a remote Linux/Unix system. More below.

3. Web browser access
   • A more recent invention is Web browser access to do ssh (command line only) or maybe get an entire GUI through the Web browser.
     This is set up for DCU, but may not be set up for other Linux systems you will meet elsewhere.

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student.computing.dcu.ie Linux account

All the remote access routes lead to your student.computing.dcu.ie Linux account.
I have my own such account, which is mhumphrysdculab
My account has the following properties:

• Home directory:
  /users/tutors/mhumphrysdculab

• Programs directory:
  /users/tutors/mhumphrysdculab/bin

• Web directory:
  /users/tutors/mhumphrysdculab/public_html

• Web page:
  https://student.computing.dcu.ie/~mhumphrysdculab

Your account will be similar (change user name and group name).

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2FA

A single password is very handy, but sadly is not very secure.
Foreign hackers run bots trying to guess passwords of ssh logins on large numbers of servers.
Your password may be hard to guess, but if there are lots of users, some will have simple passwords and the bots will get in.

DCU now uses a 2FA security system.
The idea is you need something else, that a foreign hacker will not have.
For example, it is linked to your phone.

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ssh keys

A simple form of "something a foreign hacker will not have" is to use ssh keys.
This is a key kept as a file on your computer, that must match another key on the server.
The key is huge (like around 1600 characters) so unlike a password cannot be guessed by the hacker's bot.
If you use ssh keys, you do not need the mobile phone 2FA, or even the password.

termcast - Web browser access to DCU Linux Command-line

• termcast is Web browser access to Linux command-line.
• This is your student.computing.dcu.ie account

• This is incredibly handy and fast, though only gives a command line.
• You have to use command-line Text editors like nano

• termcast.computing.dcu.ie
• Help

Use termcast to set up 2FA

• 2FA help

• How to set up 2FA:
  1. Download the Google Authentication app
  2. Login to termcast
  3. Shows barcode - Some of it may be off screen - Scroll up / reduce font size
  4. Scan barcode with Google Authentication app
  5. From now on, Google Authentication app will display a changing 2FA "verification code" that you enter when you need to login.
  6. In fact, even better: From now on, termcast itself uses ssh keys so you can skip password and skip 2FA code.
  7. Other clients may need password and 2FA code. But in fact we can use ssh keys with them too.

Change color on termcast

• (I often use US spelling "color" since all the technology does.)
• ANSI escape codes can be used to set text and background color of a Linux command-line window like termcast.

  # reverse the default termcast colors: 
  # black text on white background
  printf '\e[30;107m'
  

• See Colors table.
• Can set color for one word and then change it back.
• The color settings can get reset by other commands though. And often are.
• I can make it an alias so I can type it again easily:

  alias revcolor=" printf '\e[30;107m' ; clear "
  

• Then I can type "revcolor" to reverse the colors again.
• But temporary color change is not ideal. See How to permanently change color.

ssh

ssh is the normal way globally of getting command-line access to a Linux/Unix system.
(Web interfaces like termcast are not so common.)

• ssh
• ssh student.computing.dcu.ie

• CA tech support
  • ssh
  • ssh with keys

• ssh to DCU Linux needs the password plus the 2FA verification code from Google Authentication app, as explained above.

• On ssh you can use command-line Text editors like nano

• Windows ssh clients
  • AbsoluteTelnet (not free)

• On Apple Mac: Terminal - ssh

Windows ssh client: PuTTY

• PuTTY (free)
• PuTTY download
• PuTTY FAQ

• Some settings you might change:
  • Connection - Data - username
  • Right-click bar - Change settings - Colors - Use system colors
  • Change settings - Appearance - Change font
  • Stop sessions timing out when idle: Connection - "Seconds between keepalives" - set value to say 30
  • Window - Behaviour - Warn before close - off

• Copy-and-paste is strange on PuTTY:
  • Copy - Select text
  • Paste - Right-click (or Shift-Insert)
• Right-click Paste is rather dangerous, so you can change this:
  • Window - Selection - Right brings up menu

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Set up ssh using ssh keys

Using ssh with password and 2FA is awkward.
So if you are using ssh, set up ssh keys.

• termcast is already using ssh keys
  • It keeps a persistent session, even if you close the tab.
  • It holds the "public" key in ~/.ssh/authorized_keys
  • Take a look at it. It is a text file.

• To set up ssh keys for your ssh client:
  1. Login to Linux
  2. Generate keypair:

      cd $HOME/.ssh
      ssh-keygen -t rsa
     

     Hit enter to accept default filename.
     Hit enter to skip passphrase.
  3. Result is private and public key files:
     • id_rsa
     • id_rsa.pub
  4. Append public key to authorized_keys:

      cat id_rsa.pub >> authorized_keys 

  5. Copy private key to your PC.

  6. You can then tell your ssh client to use this private key instead of a password. You need to tell it username.
  7. You will find it logs you in with no password and no 2FA.

USB key

To transfer files to/from USB key:

• /media/disk
• media icon on desktop - Unmount

PuTTY with private key

• To use private key with PuTTY client.
• Auth - Credentials - select file

• PuTTY does not like some private keys generated on Linux server.
• Solution: Puttygen "Import key" and fix format.

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sftp

sftp or similar is the normal way of getting remote read-write file system access to Linux/Unix systems.

• sftp
• sftp to student.computing.dcu.ie

• Windows sftp client: WinSCP (free)
  • Download
  • "Synchronise" to synch two folders

• Odd ongoing issue with sftp:
  • Shell initialization (.profile, .bashrc, .cshrc, etc) must be silent. If shell initialization echo's output, ssh will work but sftp will fail.

• Other sftp clients

• Remote and Network Computing

Use ssh keys

• Set up your sftp client to use ssh keys, like above.
• You may find it impossible to sftp otherwise, given our 2FA system.
• You tell your sftp client to use the private key instead of a password. You need to tell it username. You will find it logs you in with no password and no 2FA.

Turn an sftp site into a drive

If (as is common) you have a Windows client and a Linux server, you can use sftp to turn the Linux server into a drive on Windows, like the X: drive.

• How to turn an ftp site into a drive.

• Then just use Windows programs like Notepad++ and NoteTab to edit files on the X: drive.

Use your own Linux

On Windows - Recommended

• Linux shell on Windows 10

On Windows - Other

• Run Linux in a "virtual machine"
  • VMware Workstation
    1. Install VMware Workstation Player (free)
    2. Download Ubuntu
    3. Install Ubuntu with VMware

• Dual boot Linux and Windows.
  • openSUSE
    • Installation (and here)

On Mac

• Terminal

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On the Internet since 1987.      New 200 G VPS server.

Note: Links on this site to user-generated content like Wikipedia are highlighted in red as possibly unreliable. My view is that such links are highly useful but flawed.