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## login
![TRON: Legacy](tron.jpg)
> In the movie _TRON: Legacy_, Linux is rebranded "SolarOS" in reference to [Solaris](<https://en.wikipedia.org/wiki/Solaris_(operating_system)>), another Unix OS
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Start the VM to boot the previously installed Debian system.
Do the following for both a user and the [superuser](https://en.wikipedia.org/wiki/Superuser) (`root`) :
- Log in
- Clear the console using the keyboard shortcut
- Change the password to a space : `" "`
- Show the command history using five keystrokes or less (using autocompletion)
- Log out using the keyboard shortcut
### Just numbers
Login as [`root`](https://en.wikipedia.org/wiki/Superuser) on the third [Linux console](https://en.wikipedia.org/wiki/Linux_console).
Check the Internet connectivity with the command `ping google.com`.
After a few hops, interrupt the program with : <kbd>Ctrl</kbd> + <kbd>C</kbd>.
Behind every name in a computer system there is a number (ID, index, address, etc) :
- User identifier
- `root``0`
- `student``1000`
- IP address
- google.com → 216.58.214.14 (quad-dotted notation) → `3627734542`
- tencent.com → 117.169.101.44 (quad-dotted notation) → `1974035756`
- File inode
- `/etc/fstab``44696029`
- `.profile``59639363`
- Port
- `HTTP``80`
- `HTTPS``443`
- Process identifier
- `cron``254`
Names exist because they are human readable, but behind the scenes they are converted into numbers, unique in their namespace :
- A domain name can have several IP addresses, but an IP address can only identify one domain name
- Several processes may have the same name, but a PID identifies a single process
Find the commands to get :
- the inode of a specific file
- the current user ID
- the PID of a program, for example `bash`