Add day_3 files

src/SUMMARY.md

@@ -11,5 +11,7 @@
   - [Shell glue](day_2/glue.md)
   - [Tasks](day_2/tasks.md)
 - [Day 3](day_3/README.md)
+  - [Notes](day_3/notes.md)
+  - [Tasks](day_3/tasks.md)
 - [Day 4](day_4/README.md)
 - [Day 5](day_5/README.md)

src/day_2/tasks.md

@@ -30,7 +30,13 @@ We will use the program `inotifywait`. This program can monitor a directory and
 1. Based on the output, choose an event that you want to listen to with `inotifywait` that tells you when a file is _completely_ added to the directory `jobs`. Use the manual to read more about specific events.
 1. Find an option that lets you tell `inotifywait` to only notify when the choosen event occurs.
 1. Find an option that lets you format the output of the notification of `inotifywait`. Since we only listen on one event and monitor only one directory, an output that shows only the name of the new file should be enough.
-1. Enter the command that you have until now in a script. Now extend it by using a `while` loop that continously listens on the notifications of `inotifywait`.
+1. Enter the command that you have until now in a script. Now extend it by using a `while` loop that continously listens on the notifications of `inotifywait`. Use the following snippet while replacing the sections with `(...)`:
+   ```bash
+   inotifywait (...) | while read FILENAME
+   do
+       (...)
+   done
+   ```
 1. After a notification, the body of the `while` loop should first print the name of the script that was added. From now on, we only want to add scripts to the `jobs` directory.
 1. After printing the script name, run the script!
 1. Save the standard output and standard error of the script into two separate files in the `logs` directory. If the name of the script is `job.sh` for example, then the output should be in the files `logs/job.sh.out` and `logs/job.sh.err`.
@@ -56,6 +62,33 @@ If the name of the job script is `job.sh` for example, the job script should be
 
 Use variables to write the script to make it more understandable.
 
+#### Help
+
+To save the output of a command into a variable, use you have to use the following syntax:
+
+```bash
+DATE=$(date ...)
+```
+
+Replace `...` with your code.
+
+To read the `n`-th argument that is provided to a script you write, you have to use `$n`.
+
+Example script called `arg.sh`:
+
+```bash
+#!/usr/bin/bash
+
+echo "The first argument is: $1"
+```
+
+When you run this script with an argument:
+
+```console
+$ ./arg.sh "Hello"
+The first argument is: Hello
+```
+
 ## Task: Submit a job
 
 Write a small scripts of your choice that require a long time to run and submit them using the script from the last task. Make sure that the scheduler is running in the background.

src/day_3/notes.md

@@ -0,0 +1,336 @@
+# Notes
+
+## Shell tricks
+
+### Expansion
+
+```bash
+# mkdir -p dir/sub1 dir/sub2
+mkdir -p dir/sub{1,2}
+
+# touch dir/sub1/file1.txt dir/sub1/file2.txt
+touch dir/sub1/file{1,2}.txt
+
+# cp dir/sub1/file1.txt dir/sub1/file1.txt
+cp dir/sub1/file1.txt{,.bak}
+```
+
+### Globbing
+
+```bash
+# Print content of all files ending with `.sh`
+cat *.sh
+
+# Move all files visible files and directories from dir1 to dir2
+mv dir1/* dir2
+
+# Move all hidden files and directories from dir1 to dir2
+mv dir1/.* dir2
+
+# Move all visible and hidden files and directories from dir1 to dir2
+# mv dir1/* dir1/.* dir2 
+mv dir1/{,.}* dir2
+```
+
+## Cargo
+
+```bash
+# Install. openssl-devel needed for cargo-update
+sudo dnf install cargo openssl-devel
+
+# To be able to run cargo install-update -a
+cargo install cargo-update
+
+# Install crate (package)
+cargo install CRATENAME
+
+# Update installed crates
+cargo install-update -a
+```
+
+## bashrc
+
+You write at the end of `~/.bashrc`.
+
+### PATH
+
+Add Cargo binaries to `PATH`:
+
+```bash
+export PATH="$PATH:$HOME/.cargo/bin"
+```
+
+### Alias
+
+```bash
+alias rm="trash"
+```
+
+## Fish
+
+`~/.config/config.fish`
+
+```bash
+if status is-interactive
+    # Disable greeting message
+    set -g fish_greeting
+
+    # Abbreviations
+    abbr -ag cp "cp -i"
+    abbr -ag mv "mv -i"
+    abbr -ag rmr "rm -r"
+    abbr -ag rm "trash"
+    abbr -ag rsync "rsync -Lahz"
+
+    # Aliases
+    alias cat "bat"
+    alias lg "lazygit"
+
+    # Functions
+    function demo
+        echo "Hallo from demo function!"
+        echo "Arguments taken: $argv"
+        echo "First argument: $argv[1]"
+    end
+end
+```
+
+Add to path:
+
+```bash
+fish_add_path ~/.cargo/bin
+fish_add_path ~/.local/bin
+```
+
+## SSH
+
+### Setup host
+
+In `~/.ssh/config`
+
+```
+Host HOST
+    HostName SERVERIP
+    User SERVERUSER
+```
+
+### Generate key pair
+
+```bash
+ssh-keygen -t ed25519 -C "COMMENT"
+```
+
+Leave blank to take default for the prompt `Enter file in which to save the key (/home/USERNAME/.ssh/id_ed25519)`.
+
+Then enter a passphrase for your key. **You should not leave it blank!**
+
+### Add public key to server
+
+```bash
+ssh-copy-id -i ~/.ssh/id_ed25519.pub HOST
+```
+
+### Connect
+
+```bash
+ssh HOST
+```
+
+### Config on server
+
+**Very important for security!** Only after adding the public key to the server!
+
+> WARNING ⚠️ :
+>
+> Verify that you are only asked for the passphrase of the SSH key before continueing in this section!
+>
+> If you are asked for the password of the user on the server when connecting, then the authentication with a key did not work. Therefore, don't set `PasswordAuthentication no`! Fix the issue with the key authentication first. **Otherwise, you will be locked out of the server!** ⚠️
+
+In `/etc/ssh/sshd_config` on the server:
+
+Uncomment line with `PasswordAuthentication` and set it to `PasswordAuthentication no`
+
+Save and exit, then run:
+
+```bash
+sudo systemctl restart sshd
+```
+
+If you are locked out after running this command, then you did not take the warning above seriously!
+
+### Copy files
+
+From server:
+
+```bash
+scp HOST:SRC_PATH DEST_PATH
+```
+
+To server:
+
+```bash
+scp SRC_PATH HOST:DEST_PATH
+```
+
+Options:
+
+- `-r`, `--recursive`: For directories.
+
+## Rsync
+
+From server:
+
+```bash
+rsync -Lahz HOST:SRC_PATH DEST_PATH
+```
+
+To server:
+
+```bash
+rsync -Lahz SRC_PATH HOST:DEST_PATH
+```
+
+Options:
+
+- `-a`, `--archieve`: Set of useful options to preserve permissions, use recursive mode, etc.
+- `-h`, `--human-readable`: Output number in a human-readable format.
+- `-z`, `--compress`: Use compression.
+- `--partial`: Continue after interruption.
+- `-L`, `--copy-links`: Copy links.
+- `-v`, `--verbose`: Show more infos.
+- `--delete`: Delete files from `DEST_PATH` if they don't exist on `SRC_PATH` anymore. **Use with caution!!!**
+
+## Systemd
+
+Check status of a service:
+
+```bash
+sudo systemctl status SERVICENAME
+```
+
+Enable service:
+
+```bash
+sudo systemctl enable SERVICENAME
+```
+
+Start service:
+
+```bash
+sudo systemctl start SERVICENAME
+```
+
+Enable and start service at the same time:
+
+```bash
+sudo systemctl enable --now SERVICENAME
+```
+
+Disable service:
+
+```bash
+sudo systemctl disable SERVICENAME
+```
+
+Stop service:
+
+```bash
+sudo systemctl stop SERVICENAME
+```
+
+Disable and stop service at the same time:
+
+```bash
+sudo systemctl disable --now SERVICENAME
+```
+
+## Firewalld
+
+Install and enable firewalld:
+
+```bash
+sudo dnf install firewalld
+sudo systemctl enable --now firewalld
+```
+
+View open ports and services:
+
+```bash
+sudo firewall-cmd --list-all
+```
+
+Open ports 80 (http) and 443 (https):
+
+```bash
+sudo firewall-cmd --add-service http
+sudo firewall-cmd --add-service https
+sudo firewall-cmd --runtime-to-permanent
+```
+
+or:
+
+```bash
+sudo firewall-cmd --add-port 80/tcp
+sudo firewall-cmd --add-port 443/tcp
+sudo firewall-cmd --runtime-to-permanent
+```
+
+## Podman
+
+```bash
+# Search for image
+podman search python
+
+# Pull image
+podman pull docker.io/library/python:latest
+
+# See pulled images
+podman images
+
+# Run container and remove it afterwards
+podman run -it --rm docker.io/library/python:latest bash
+
+# Create network
+podman network create NETWORKNAME
+
+# Create container
+podman create \
+    --name CONTAINERNAME \
+    --network NETWORKNAME \
+    -e ENVVAR="Some value for the demo environment variable" \
+    --tz local \
+    docker.io/library/python:latest
+
+# Start container
+podman start CONTAINERNAME
+
+# Enter a running container
+podman exec -it CONTAINERNAME bash
+
+# Stop container
+podman stop CONTAINERNAME
+
+# Generate systemd files
+podman generate systemd --new --files --name CONTAINERNAME
+
+# Create directory for user's systemd services
+mkdir -p ~/.config/systemd/user
+
+# Place service file
+mv container-CONTAINERNAME.service ~/.config/systemd/user
+
+# Activate user's service (container)
+systemctl --user enable --now container-CONTAINERNAME
+```
+
+Keep user's systemd services live after logging out:
+
+```bash
+sudo loginctl enable-linger USERNAME
+```
+
+Options:
+
+- `-v`, `--volume`: `SRC_PATH:DEST_PATH:L`. Label should be one of `z`, `z,ro`, `Z` or `Z,ro`.
+- `--label "io.containers.autoupdate=registry"` for `podman auto-update`
+- `-p`, `--publish`: `SERVER_PORT:CONTAINER_PORT`

src/day_3/tasks.md

@@ -0,0 +1,131 @@
+# Tasks
+
+Do the tasks in the given order! They depend on each other.
+
+## Task 1: Cargo
+
+Use `cargo` to install the following crates:
+
+- cargo-update
+- tealdeer
+
+It might take a long time to compile everything.
+
+Add `$HOME/.cargo/bin` to your `PATH`.
+
+`cargo-update` should be installed to be able to run `cargo install-update -a` to update all installed crates. Try running the command. But you should not find any updates since you did just install the crates.
+
+The crate `tealdeer` provides you with the program `tldr`.
+
+Run `tldr --update`. Now run the following two commands:
+
+```bash
+tldr dnf
+tldr apt
+```
+
+It should be obvious to you what `tldr` does after you run the commands. Try it with other programs than `dnf` and `apt`!
+
+## Task 2: SSH
+
+Generate a SSH key pair and send me the public key per email: mo8it@proton.me
+
+Enter a passphrase while generating the key pair!
+
+Don't send me the private key!!! **You should never send your private SSH keys to anyone!**
+
+The public key ends with `.pub`.
+
+I will then append your public key to `~/.ssh/authorized_keys` on the server that we will use in the next tasks. After I add your public key, you will be able to login to the server and do the next tasks.
+
+Create the file `~/.ssh/config` and add the server as a host with the name `linux-lab`.
+
+Enter this IP: 45.94.58.19
+Enter this user: admin
+
+After that I add you public key, connect to the server using the host name that you did enter in `~/.ssh/config` which should be `linux-lab`.
+
+## Task 3: User creation
+
+1. Create a user for you on the server after connecting with SSH. To do so, run:
+   ```bash
+   sudo useradd USERNAME
+   ```
+
+   Replace `USERNAME` with your name.
+
+1. Now set a password for the new user:
+
+   ```bash
+   sudo passwd USERNAME
+   ```
+1. For the new user to be able to use `sudo`, it has to be added to the `wheel` group:
+
+   ```bash
+   sudo usermod -aG wheel USERNAME
+   ```
+
+   `-aG` stands for _append to group(s)_.
+
+   (On debian based distros, the user should be added to the `sudo` group instead of `wheel`.)
+
+1. Now, change your user to the new user:
+
+   ```bash
+   sudo su USERNAME
+   ```
+
+   You will see that the user name did change in the prompt.
+
+1. Run the following command for verification:
+
+   ```bash
+   whoami
+   ```
+
+   It should not output "admin"!
+
+   Yes, the command is called `whoami`. Linux is kind of philosophical 🤔
+
+1. Now, verify that you can run `sudo` as the new user:
+
+   ```bash
+   sudo whoami
+   ```
+
+   You should see "root" as output because `sudo` runs a command as the `root` user.
+
+1. `cd` to the home directory of the new user.
+1. Make sure that you are in the home directory of the new user! Run `pwd` to verify that you are NOT in `/home/admin`. **`PLEASE DON'T TOUCH /home/admin/.ssh`** ⚠️ . Now, create the directory `~/.ssh` in the home directory of the new user. Change the permissions of `~/.ssh` such that only the user has read, write and execution permissions. _group_ and _others_ should have no permissions for `~/.ssh`!
+1. Create the file `authorized_keys` inside `~/.ssh`. Only the user should have read and write permissions for the file. _group_ and _others_ should have no permissions for the file!
+1. Copy the content of your public key file (with `.pub` as extention) to this file. It should be one line! Then save the file.
+1. Logout from the server. Go to `~/.ssh/config` that you did write at the beginning of this task. Change the user for the host `linux-lab` from `admin` to `USERNAME` where `USERNAME` is the name of the new user that you did create on the server.
+1. Try to connect using the host name again. If you did everything right, you should be connected and be the user that you did create. Run `whoami` to verify that the output is not "admin".
+
+## Task 4: File transfer
+
+Use `scp` and then `rsync` to transfer the files that you did create during the course to the server `linux-lab`.
+
+Do you notice any differences between the two commands?
+
+## Task 5: Nextcloud
+
+In this task you will deploy your own cloud on the server: Nextcloud!
+
+To do so, we will install Nextcloud as a container using `podman`.
+
+In this task, you should connect as the user `admin` to the server. **Don't do this task as the user that you did create in the last task!** ⚠️
+
+To connect as `admin` again, change the user for the host `linux-lab` in `~/.ssh/config` back to `admin` or use `ssh admin@linux-lab` instead of only `ssh linux-lab`.
+
+You can find more information about the Nextcloud container here: https://hub.docker.com/\_/nextcloud
+
+Create a directory called `nextcloudN` in the home directory of the user `admin`. `N` at the end stands for the number that you are using in the url to connect to the browser terminal `ttydN.mo8it.xyz`.
+
+Create a container with the following options:
+
+- Container name: nextcloudN. `N` at the end stands for the number that you are using in the url to connect to the browser terminal `ttydN.mo8it.xyz`.
+- Timezone: local
+- Network: traefik
+- Volume: Mount the directory `nextcloudN` that you did create into `/var/www/html` in the container. Use the label `Z`!
+- ... (I will continue the task description during the lunch break)