# Linux Administration

# Boot

# Grub

#### Setting the default runlevel in Ubuntu 16.04

Mapping between runlevels and systemd targets  
  
Runlevel / Target

0: poweroff.target  
1: rescue.target  
2, 3, 4: multi-user.target  
5: graphical.target  
6: reboot.target

To change runlevel:

sudo systemctl isolate multi-user.target

  
To set the default runlevel:

sudo systemctl enable multi-user.target  
sudo systemctl set-default multi-user.target

#### Adding Operating Systems to Linux grub bootloader

Open a new terminal  
Execute the following commands:

```
sudo os-prober		#this will search for the OSs
sudo update-grub	#this will update your grub bootloader
```

# Bibliography

[https://askubuntu.com/questions/788323/change-runlevel-on-16-04](https://askubuntu.com/questions/788323/change-runlevel-on-16-04)  
[http://www.hypexr.org/linux\_scp\_help.php](http://www.hypexr.org/linux_scp_help.php)

# File management

#### Scp file copy examples

Copy the file "foobar.txt" from a remote host to the local host  
$ scp your\_username@remotehost.edu:foobar.txt /some/local/directory

  
Copy the file "foobar.txt" from the local host to a remote host  
$ scp foobar.txt your\_username@remotehost.edu:/some/remote/directory

# Services

#### Enabling ssh on Ubuntu

```
sudo apt-get install openssh-server
sudo service ssh status
```

#### Removing the CD / DVD install as a source for apt-get

```
sudo nano /etc/apt/sources.list
```

\#comment cdrom line

```
sudo apt-get update
```

# Scripting

# Colours on terminal

```PHP
<?php
/*
Black 0;30
Blue 0;34
Green 0;32
Cyan 0;36
Red 0;31
Purple 0;35
Brown 0;33
Light Gray 0;37 
Dark Gray 1;30
Light Blue 1;34
Light Green 1;32
Light Cyan 1;36
Light Red 1;31
Light Purple 1;35
Yellow 1;33
White 1;37
*/
```

```PHP
<?php
  echo "\033[31m some colored text \033[0m some white text \n";
  echo "\033[32m some colored text \033[0m some white text \n";​
```

http://blog.lenss.nl/2012/05/adding-colors-to-php-cli-script-output/