How to login to Linux at DCU

There are many different ways to use Linux at DCU.

Sysadmin help and my help

The School of Computing ("CA") has its own Linux and Windows sysadmins.
They have a guide to how to login. See below.
This page has my notes, but you may not need them.
Also the sysadmins run the Linux server, and they make changes, and may not immediately tell me the changes.
So if there is any difference between my notes and theirs, go with theirs. (And tell me the updates.)
Talk to the CA sysadmins for all password issues, not me.
You can email them at:
```
 support@computing.dcu.ie 
```

Sysadmins pages

docs.computing.dcu.ie (CA sysadmins)
- FAQ
- How to login to student server
DTS (formerly ISS) (DCU sysadmins)
- help (login needed)
- public help pages

Overview - Remote access to DCU Linux

Access from home and from Windows.

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

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:

 /users/student/USERID 
 /users/student/USERID/bin 
 /users/student/USERID/public_html
 https://student.computing.dcu.ie/~USERID

MFA

A single password is very handy, but sadly is not very secure.
Globally, 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 uses a 2FA or MFA security system for many things.
The idea is you need something else, that a hacker will not have.
For example, it is linked to your phone.

DCU help pages
- Student Onboarding Self Help Guide
- How to install MFA phone app at DCU

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 to login to Linux, you do not need MFA or password.

termcast - Web browser access to DCU Linux Command-line

termcast is Web browser access to your DCU Linux account (command-line only).
This is your student.computing.dcu.ie account
termcast is a DCU invention by Steve Blott.
Web browser access to Linux command-line login is not very common, and there is no standard app.
At DCU, termcast gives you command line access to your Linux account.
You have to use command-line text editors like nano
termcast.computing.dcu.ie
Help page
termcast saves your session so when you connect again you can continue where you left off.
2nd server: labcast.computing.dcu.ie

Notes for later

How to 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
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

How to set up ssh keys

CA student server requires ssh with ssh keys, not with password.
When you set up ssh keys, you can use ssh and sftp without password or MFA.
How to login to student server (CA help)
- How to set up ssh keys

My notes on ssh keys

(May not be needed. See CA notes above.)

Login to Linux
Setup a .ssh directory if it does not exist
```
 mkdir ~/.ssh 
```
Generate keypair using ssh-keygen
```
 cd ~/.ssh
 ssh-keygen 
```
Hit enter to accept default filename.
Hit enter to skip passphrase.
Result is private and public key files:
- id_rsa
- id_rsa.pub
Append public key to authorized_keys:
```
 cat id_rsa.pub >> authorized_keys 
```
Hide authorized_keys:
```
chmod go-rwx ~/.ssh 
chmod go-rwx ~/.ssh/authorized_keys 
```
This is important. Clients may generate cryptic errors if authorized_keys is not hidden.
Copy private key to your PC. There could be various ways of doing this.
To use private key with PuTTY:
- PuTTY does not like some private keys generated on Linux server.
- Solution: Puttygen "Import key" and fix format.
- Auth - Credentials - select file
Now you have a private key on your PC, you tell your ssh and sftp clients to use this private key instead of a password. You need to tell it username.
You will find it logs you in with no password and no MFA.

USB key

One way of transferring files to/from your Linux account:

Insert USB key.
It appears under: /media/disk
media icon on desktop - Unmount

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
Other sftp clients
Remote and Network Computing
You can set up ssh keys to run sftp without password or MFA.

Notes for later

How to 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.

sftp likes a silent shell

There is an 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.

Use your own Linux

On Windows

Linux shell on Windows

On Mac

Terminal
(Apple desktop machines have a form of Unix underneath.)

Notes for later

Other ways to set up Linux on a Windows machine

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)