360 lines
6.7 KiB
Markdown
360 lines
6.7 KiB
Markdown
---
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title: "Basics"
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tags: [ "Documentation", "Basics" ]
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---
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You need about a dozen commands to move around Linux.
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After that, you look up the rest as you go.
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Don't worry about understanding any of it, just type it in and the habit forms pretty quickly.
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You start in a dark room. You want to know where you are by **p**rinting out your **w**orking '**d**irectory' (i.e. 'location'):
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```bash
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pwd
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```
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Have a look at what is here:
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```bash
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ls
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```
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If you get no response, the list of items is "", meaning "nothing here".
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Have a look at **a**ll the files:
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```bash
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ls -a
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```
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```bash
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. ..
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```
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So `.` means 'here' and `..` means 'you see stairs leading downwards' (e.g. 'the directory behind you').
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Change directory (`cd`) down one level:
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```bash
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cd ..
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```
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Look where you are again with `pwd`, then go back up. Use `ls`, and if you see `bob`, then:
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```bash
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cd bob
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```
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Move around the directories. The place at the bottom is the 'root', and is known as `/`. Go to the root:
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```bash
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cd /
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```
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Do `ls` again and `cd` into `etc`. Look at how much space those folders are taking up:
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```bash
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du iptables
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```
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That's the number of kilobytes the file is taking up.
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Do the same again, but in a human-readable format:
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```bash
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du -h iptables
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```
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The `du` program has `-h` for 'human', '-s' for 'short', and a bunch of other commands.
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Have a look at the manual and try another command:
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```bash
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man du
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```
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Once you're done, press 'q' to quit the manual page and try the extra `du` flag you've found.
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Now you can try to gain super-powers and take over the system:
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```bash
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sudo -i
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```
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At this point, you are 'root'.
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All your commands will be executed, even if they're unsafe, or even if you ask to delete the entire machine.
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Best to exit out of the root account:
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```bash
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exit
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```
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Go find a file that isn't a directory. You can tell which is which with:
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```bash
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ls -l
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```
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A directory starts with a 'd', like this:
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```bash
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drwxr-xr-x 79 root root 4096 Jan 3 05:15 /etc/
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```
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A standard file starts with '-', like this:
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```bash
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`-rw-r--r-- 1 root root 8 Dec 11 17:26 hostname`
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```
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Look inside the file /etc/hostname to find out your computer's name:
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```bash
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cat /etc/hostname
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```
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Print out the words "hello world":
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```bash
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echo "hello world"
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```
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Move back to your home directory:
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```bash
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cd
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```
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Take the words 'hello world', and put them in 'my_file':
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```bash
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echo 'hello world' > my_file
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```
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Measure the disk usage of that file, then put the results at the bottom of the file:
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```bash
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du $FILE >> $FILE
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```
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And check the results:
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```bash
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cat $FILE
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```
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# Autocompletion
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Press tab after typing a few keys and bash will guess what you're trying to type.
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# Permissions
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Look at your file's owner:
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```bash
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ls -l $FILE
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```
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If it says `-rw-r--r-- 1 root root 8 Dec 11 17:26 hostname` then the file is owned by 'root'.
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Take your file and change the owner to root:
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```bash
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sudo chown root $FILE
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```
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Change the same file so it's owned by the group 'audio':
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```bash
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sudo chown :audio $FILE
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```
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Check you did that correctly:
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```bash
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ls -l my_file
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```
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> -rw-r--r-- 1 root audio 0 Jan 3 19:20 my_file
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Read the start of that line. Root can 'read' and 'write' to or delete the file. Try to remove (delete) it:
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```bash
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rm $FILE
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```
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You'll see you're not allowed, because you don't own it.
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Look at which groups you're in:
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```bash
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groups
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```
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Change the file so that members of the audio group can write to the file:
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```bash
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sudo chmod g+w $FILE
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```
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Check you got it right with `ls -l`:
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```bash
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-rw-rw-r-- 1 root audio 0 Jan 3 19:20 my_file
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```
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Try to delete the file again:
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```bash
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rm my_file
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```
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If you can't, you're not in the audio group. Add yourself. You'll need to *modify* your *user account*, by **a**ppending 'audio' to your list of groups.
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Use `-a` to **a**ppend, and `-G`, to say you're modifying groups:
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```bash
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sudo usermod -a -G audio [ your username here ]
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```
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Now you should be able to remove (delete) the file. Remember, that using 'rm file' will not send it to a recycling bin. The file is gone.
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# Directories
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Make a directory called 'new test':
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```bash
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mkdir 'new test'
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```
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Make two directories, called 'A', and 'Z':
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```bash
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mkdir A Z
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```
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Make a single directory called 'A Z'
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```bash
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mkdir 'A Z'
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```
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# Text Searches
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Measure the disk usage of everything ('\*' means 'everything'), and put it in a file called 'disk usage.txt':
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```bash
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du -sch * > A/'disk usage'.txt
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```
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Look at your file:
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```bash
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cat A/'disk usage.txt'
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```
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If you think you have too much information, use `grep` to just get the one line of text you want:
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```bash
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grep total A/disk\ usage.txt
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```
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The `grep` program also has a manual ('man page'). You should find out what that `-c` flag does, but the manual is too long to read.
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Start the manual:
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```bash
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man du
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```
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Then search for `-c` by pressing `/`. Your final keys should be `man du`, then `/-c`
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Find out if the `ls` program also has a 'human readable' format by using `grep` to search for the word 'human':
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```bash
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man ls | grep human
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```
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Now use that flag that you've found in combinatin with the `-l` flag to look at a file.
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Remove the directory 'Z':
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```bash
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rmdir Z
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```
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Remove the directory 'Z':
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```bash
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rmdir Z
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```
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And then remove all the rest:
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```bash
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rmdir *
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```
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The 'A' directory will not budge because it's not empty. Remove it recursively, so the computer will remove the things inside the directory as well as the directory itself:
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```bash
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rm -r A
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```
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# Installation
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You get a package manager which installs programs, fonts, et c.
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If you're on something like Debian, you'll have `apt`, or if you're on something like Red Hat, you'll have `yum`.
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If unsure, ask where a program is:
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```bash
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whereis yum
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```
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```bash
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whereis apt
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```
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If you get a hit, you can use whatever program that is to install things.
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Set a reminder of your package manager:
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```bash
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echo my package manager is yum | lolcat
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```
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If that failed it's because you don't have `lolcat` installed.
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Install lolcat:
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```bash
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sudo apt install lolcat
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```
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Try the same command again.
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Search for things you want, like `libreoffice`, or `gimp`:
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```bash
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apt search libreoffice
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```
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... then install one of them with:
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```bash
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apt install $PROGRAM
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```
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Remove `lolcat`, because it's useless:
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```bash
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sudo apt remove lolcat
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```
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... and that's pretty much it. You can move, create, destroy, install things, and look things up.
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# Review
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- Search for random things with your package manager and install the interesting ones.
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* Read the manual with `man thing`
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* If it's useless, remember to uninstall it.
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- Have a look around the file system in `/`.
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- Look in the `.config` folder in your home directory.
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* If you copy a program's config to another machine, the program will behave just like you set it up in your own machine.
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