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38 changes: 38 additions & 0 deletions lessons/locales/da_danish/access/file-permissions.md
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# Filtilladelser

## Lektionsindhold

Som vi tidligere har lært, har filer forskellige tilladelser eller filtilstande. Lad os se på et eksempel:

<pre>
$ ls -l Desktop/
drwxr-xr-x 2 pete pingviner 4096 dec 1 11:45.
</pre>

Der er fire dele til en fils tilladelser. Den første del er filetypen, som betegnes af det første tegn i tilladelserne, da vi ser på en mappe, vises der <b>d</ b> for filetypen. Mest almindeligt ser du en <b>-</ b> for en almindelig fil.

De næste tre dele af filtilstanden er de faktiske tilladelser. Tilladelserne er grupperet i 3 bits hver. De første 3 bits er brugerrettigheder, derefter gruppetilladelser og derefter andre tilladelser. Jeg har tilføjet røret for at gøre det lettere at differentiere.

<pre>d | rwx | r-x | r-x </pre>

Hvert tegn repræsenterer en forskellig tilladelse:
<ul>
<li>r: læsbar</li>
<li>w: skrivbar</li>
<li>x: eksekverbar (stort set et eksekverbart program)</ li>
<li>-: tom</li>
</ul>

Så i ovenstående eksempel ser vi, at brugeren pete har læs, skriv og eksekver tilladelser på filen. Gruppen penguins har læs og eksekver tilladelser. Og til sidst har de andre brugere (alle andre) læs og eksekver tilladelser.

## Øvelse

Brug kommandoen ls -l på flere filer og recitér deres tilladelser, bruger og gruppe.

## Quiz Spørgsmål

Hvilken tilladelsesbit bruges for eksekverbar?

## Quiz Svar

x
56 changes: 56 additions & 0 deletions lessons/locales/da_danish/access/modifying-permissions.md
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# Ændring af Tilladelser

## Lektionsindhold

Ændring af tilladelser kan nemt gøres med kommandoen <b>chmod</b>.

Først skal du vælge hvilken tilladelse du vil ændre, bruger, gruppe eller andre. Du kan tilføje eller fjerne tilladelser med et <b>+</b> eller <b>-</b>, lad os se på nogle eksempler.

<b>Tilføjelse af tilladelsesbit på en fil</b>
<pre>$ chmod u+x myfile</pre>

Kommandoen ovenfor læses som dette: Skift tilladelse til myfile ved at tilføje eksekverbar tilladelsesbit på brugersættet. Så nu har brugeren eksekverbar tilladelse til denne fil!

<b>Fjernelse af tilladelsesbit på en fil</b>
<pre>$ chmod u-x myfile</pre>

<b>Tilføjelse af flere tilladelsesbits på en fil</b>
<pre> $ chmod ug + w </pre>

Der er en anden måde at ændre tilladelser ved hjælp af numerisk format. Denne metode giver dig mulighed for at ændre alle tilladelser på én gang. I stedet for at bruge r, w eller x til at repræsentere tilladelser, bruger du en numerisk repræsentation for et enkelt tilladelsessæt. Så det er ikke nødvendigt at angive gruppen med g eller brugeren med u.

De numeriske repræsentationer ses nedenfor:

<ul>
<li>4: læs tilladelse</li>
<li>2: skriv tilladelse</li>
<li>1: eksekver tilladelse</li>
</ul>

Lad os se på et eksempel:

<pre>$ chmod 755 myfile</pre>

Kan du gætte hvilke tilladelser vi giver denne fil? Lad os bryde det ned, så nu dækker 755 tilladelserne for alle sæt. Det første nummer (7) repræsenterer brugerrettigheder, det andet nummer (5) repræsenterer gruppetilladelser, og de sidste 5 repræsenterer andre tilladelser.

Vent et øjeblik, 7 og 5 var ikke nævnt ovenfor, hvorfra får vi disse tal? Husk at vi kombinerer alle tilladelserne til et nummer nu, så du bliver nødt til involvere lidt matematik.

7 = 4 + 2 + 1, så 7 er brugerrettighederne, og den har læs, skriv og eksekver tilladelser

5 = 4 + 1, gruppen har læs og eksekver tilladelser

5 = 4 +1, og alle andre brugere har læs og eksekver tilladelser

En ting at bemærke: Det er ikke en god idé at ændre tilladelser nilly willy, du kan potentielt udsætte en følsom fil for alle at ændre, men mange gange vil du legitimt ændre rettigheder, bare tag dine forholdsregler, når du bruger chmod-kommandoen.

## Øvelse

Skift nogle grundlæggende tekstfiltilladelser, og se bitene skifter, som du gør en ls -l.

## Quiz Spørgsmål

Hvilket tal repræsenterer læsetilladelsen, når du bruger numerisk format?

## Quiz Svar

4
34 changes: 34 additions & 0 deletions lessons/locales/da_danish/access/ownership-permissions.md
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# Ejerskabstilladelser

## Lektionsindhold

Ud over at ændre tilladelser på filer, kan du også ændre gruppen og bruger ejerskabet af filen.

<b>Rediger brugerejerskab</b>

<pre>$ sudo chown patty myfile</pre>

Denne kommando vil sætte ejeren af myfile til patty.

<b>Rediger gruppeejerskab</b>

<pre>$ sudo chgrp whales myfile</pre>

Denne kommando sætter gruppen for myfile til whales.

<b>Rediger både bruger og gruppe ejerskab på samme tid</b>
Hvis du tilføjer et kolon og gruppenavn efter brugeren, kan du indstille både brugeren og gruppen på samme tid.

<pre>$ sudo chown patty:whales myfile</pre>

## Øvelse

Rediger gruppen og brugeren af nogle testfiler. Bagefter tag et kig på tilladelserne med ls -l.

## Quiz Spørgsmål

Hvilken kommando bruger du til at ændre bruger ejerskab?

## Quiz Svar

chown
41 changes: 41 additions & 0 deletions lessons/locales/da_danish/access/process-permissions.md
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# Process Permissions

## Lesson Content

Let's segway into process permissions for a bit, remember how I told you that when you run the passwd command with the SUID permission bit enabled you will run the program as root? That is true, however does that mean since you are temporarily root you can modify other user's passwords? Nope fortunately not!

This is because of the many UIDs that Linux implements. There are three UIDS associated with every process:

When you launch a process, it runs with the same permissions as the user or group that ran it, this is known as an <b>effective user ID</b>. This UID is used to grant access rights to a process. So naturally if Bob ran the touch command, the process would run as him and any files he created would be under his ownership.

There is another UID, called the <b>real user ID</b> this is the ID of the user that launched the process. These are used to track down who the user who launched the process is.

One last UID is the <b>saved user ID</b>, this allows a process to switch between the effective UID and real UID, vice versa. This is useful because we don't want our process to run with elevated privileges all the time, it's just good practice to use special privileges at specific times.

Now let's piece these all together by looking at the passwd command once more.

When running the passwd command, your effective UID is your user ID, let's say its 500 for now. Oh but wait, remember the passwd command has the SUID permission enabled. So when you run it, your effective UID is now 0 (0 is the UID of root). Now this program can access files as root.

Let's say you get a little taste of power and you want to modify Sally's password, Sally has a UID of 600. Well you'll be out of luck, fortunately the process also has your real UID in this case 500. It knows that your UID is 500 and therefore you can't modify the password of UID of 600. (This of course is always bypassed if you are a superuser on a machine and can control and change everything).

Since you ran passwd, it will start the process off using your real UID, and it will save the UID of the owner of the file (effective UID), so you can switch between the two. No need to modify all files with root access if it's not required.

Most of the time the real UID and the effective UID are the same, but in such cases as the passwd command they will change.

## Exercise

We haven't discussed processes yet, we can still take a look at this change happening in real time:

<ol>
<li>Open one terminal window, and run the command: <b>watch -n 1 "ps aux | grep passwd"</b>. This will watch for the passwd process.</li>
<li>Open a second terminal window and run: <b>passwd</b></li>
<li>Look at the first terminal window, you'll see a process come up for passwd. The first column in the process table is the effective user ID, lo and behold it's the root user!</li>
</ol>

## Quiz Question

What UID decides what access to grant?

## Quiz Answer

effective
33 changes: 33 additions & 0 deletions lessons/locales/da_danish/access/setgid-set-group-id.md
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# Setgid

## Lektionsindhold

I lighed med den indstillede bruger ID-tilladelsesbit er der et sæt gruppe-ID (SGID) tilladelsesbit. Denne bit tillader et program at køre som om det var medlem af gruppen.

Lad os se på et eksempel:

<pre>$ ls -l /usr/bin/wall
-rwxr-sr-x 1 root tty 19024 Dec 14 11:45 /usr/bin/wall
</pre>

Vi kan nu se, at tilladelsesbiten er i gruppens tilladelsessæt.

<b>Ændring af SGID</b>

<pre>$ sudo chmod g+s myfile
$ sudo chmod 2555 myfile
</pre>

Den numeriske repræsentation for SGID er 2.

## Øvelse

Ingen øvelser til denne lektion.

## Quiz Spørgsmål

Hvilket tal repræsenterer SGID?

## Quiz Svar

2
55 changes: 55 additions & 0 deletions lessons/locales/da_danish/access/setuid-set-user-id.md
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# Setuid

## Lesson Content

There are many cases in which normal users need elevated access to do stuff. The system administrator can't always be there to enter in a root password every time a user needed access to a protected file, so there are special file permission bits to allow this behavior. The Set User ID (SUID) allows a user to run a program as the owner of the program file rather than as themselves.

Let's look at an example:

Let's say I want to change my password, simple right? I just use the passwd command:

<pre>$ passwd</pre>

What is the password command doing? It's modifying a couple of files, but most importantly it's modifying the /etc/shadow file. Let's look at that file for a second:

<pre>$ ls -l /etc/shadow

-rw-r----- 1 root shadow 1134 Dec 1 11:45 /etc/shadow
</pre>

Oh wait a minute here, this file is owned by root? How is it possible that we are able to modify a file owned by root?

Let's look at another permission set, this time of the command we ran:

<pre>$ ls -l /usr/bin/passwd

-rwsr-xr-x 1 root root 47032 Dec 1 11:45 /usr/bin/passwd
</pre>

You'll notice a new permission bit here <b>s</b>. This permission bit is the SUID, when a file has this permission set, it allows the users who launched the program to get the file owner's permission as well as execution permission, in this case root. So essentially while a user is running the password command, they are running as root.

That's why we are able to access a protected file like /etc/shadow when we run the passwd command. Now if you removed that bit, you would see that you will not be able to modify /etc/shadow and therefore change your password.

<b>Modifying SUID</b>

Just like regular permissions there are two ways to modify SUID permissions.

<i>Symbolic way:</i>
<pre>$ sudo chmod u+s myfile</pre>

<i>Numerical way:</i>
<pre> sudo chmod 4755 myfile</pre>

As you can see the SUID is denoted by a 4 and pre-pended to the permission set. You may see the SUID denoted as a capital <b>S</b> this means that it still does the same thing, but it does not have execute permissions.

## Exercise

Look at the permission for /etc/passwd in detail, do you notice anything else? Files with SUID enabled are also easily distinguishable.

## Quiz Question

What number represents the SUID?

## Quiz Answer

4
33 changes: 33 additions & 0 deletions lessons/locales/da_danish/access/sticky-bit.md
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# The Sticky Bit

## Lesson Content

One last special permission bit I want to talk about is the sticky bit.

This permission bit, "sticks a file/directory" this means that only the owner or the root user can delete or modify the file. This is very useful for shared directories. Take a look at the example below:

<pre>$ ls -ld /tmp
drwxrwxrwxt 6 root root 4096 Dec 15 11:45 /tmp
</pre>

You'll see a special permission bit at the end here <b>t</b>, this means everyone can add files, write files, modify files in the /tmp directory, but only root can delete the /tmp directory.

<b>Modify sticky bit</b>

<pre>$ sudo chmod +t mydir

$ sudo chmod 1755 mydir</pre>

The numerical representation for the sticky bit is <b>1</b>

## Exercise

What other files and directories do you think have a sticky bit enabled?

## Quiz Question

What symbol represents the sticky bit?

## Quiz Answer

t
29 changes: 29 additions & 0 deletions lessons/locales/da_danish/access/umask.md
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# Umask

## Lesson Content

Every file that gets created comes with a default set of permissions. If you ever wanted to change that default set of permissions, you can do so with the umask command. This command takes the 3 bit permission set we see in numerical permissions.

Instead of adding these permissions though, umask takes away these permissions.

<pre>$ umask 021</pre>

In the above example, we are stating that we want the default permissions of new files to allow users access to everything, but for groups we want to take away their write permission and for others we want to take away their executable permission. The default umask on most distributions is 022, meaning all user access, but no write access for group and other users.

When you run the umask command it will give that default set of permissions on any new file you make. However, if you want it to persist you'll have to modify your startup file (.profile), but we'll discuss that in a later lesson.

## Exercise

<ol>
<li>Create a new file, then note it's permissions.</li>
<li>Modify the umask and then create another new file.</li>
<li>Check the permissions once more on the new file, what do you expect to see?</li>
<ol>

## Quiz Question

What command is used to change default file permissions?

## Quiz Answer

umask
51 changes: 51 additions & 0 deletions lessons/locales/da_danish/home_page.md
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# Startside

## Græshoppe

* Kom i gang - Hvad er Linux? Kom i gang med at vælge en distribution og installation.

* Kommandolinje - Lær grundlæggende elementer i kommandolinjen, navigere filer, mapper og meget mere.

* Tekst-Fu - Lær grundlæggende tekstmanipulation og navigation.

* Avanceret tekst-Fu - Naviger tekst som en Linux-spideraben med vim og emacs.

* Brugeradministration - Lær om brugerroller og administration.

* Tilladelser - Lær om tilladelsesniveauer og ændring af tilladelser.

* Processer - Lær om de kørende processer på systemet.

* Pakker - Lær alt om dpkg, apt-get, rpm og yum pakkehåndteringsværktøjer.

## Svend

* Enheder - Lær om Linux-enheder og hvordan de interagerer med kernen og brugerrummet.

* Filsystemet - Lær om Linux-filsystemet, de forskellige typer af filsystemer, partitionering og meget mere.

* Start systemet - Lær om stadierne af Linux-opstartsprocessen.

* Kerne - Den vigtigste del af Linux-systemet, lære om, hvordan det virker, og hvordan man konfigurerer det.

* Init - Lær om de forskellige init systemer, SysV, Upstart og systemd.

* Procesudnyttelse - Lær ressourceovervågning med top, load averages, iostat og meget mere!

* Logging - Lær om systemlogfiler og /var/log biblioteket.

## Netværks Nomade

* Netværksdeling - Lær om netværksdeling med rsync, scp, nfs og mere.

* Grundlæggende om netværket - Lær grundlæggende om netværk og TCP/IP-modellen.

* Subnetting - Lær om subnet og hvordan man laver subnet aritmetik!

* Routing - Lær, hvordan pakker er routeret på tværs af netværk!

* Network Config - Lær om netværkskonfiguration ved hjælp af Linux-værktøjer!

* Fejlfinding - Lær om almindelige netværksværktøjer til at hjælpe dig med at diagnosticere og fejlfinding af problemer!

* DNS - Alt og mere, som du ønskede at vide om DNS.
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