Homelab, Linux, JS & ABAP (~˘▾˘)~
 

Category: GNU/Linux

GNU/Linux

Terminal

[Shell] User and Group management & File permissions

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  • User and Group management
    • id
    • useradd
      • -c – Full name
      • -e – Expiration date
      • -s – Default shell
      • -d – Home directory
    • passwd
    • usermod
      • -l – rename
      • -L – Lock
      • -U – unlock
    • userdel
      • -r – remove user data
    • groupadd
    • groupmod
    • gpasswd [-a -d -A] [user1, user2] [group]
    • newgrp [group]
  • su vs. su – vs. sudo
    • visudo
  • File permissions
    • UGO – User, Group, Other
    • RWX – Read, Write, Execute
    • chmod -R g+x (grant recursive execute permission to group)
      • r = 4
      • w = 2
      • x = 1
      • – = 0
      • rwxrwxrwx = 777
      • rw-rw-rw- = 666
      • rwxrwxr–- = 774
      • rw-rw—- = 660
      • rw-r—–- = 640
    • chown
    • chgrp
    • umask

https://www.sluug.org/resources/presentations/2020/2020-02-12_permissions.pdf

Software, Terminal

[Software] Using pdfunite to merge PDF documents

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First install pdfunite:

sudo apt update 
sudo apt install poppler-utils

Syntax:

pdfunite source1.pdf source2.pdf merged_output.pdf

If a pdf file is located in a different folder, you have to add the path like this: $home/Downloads/source1.pdf
If you want to merge all pdf’s of the current folder you cant type:

pdfunite *.pdf merged_output.pdf

An alternative with GUI is PDF Arranger.

Terminal

[Terminal] Shorcut overview

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Further shortcuts:

Ctrl-LCleans the screen
Ctrl-YPastes back the stuff erased by Ctrl-K or Ctrl-U
Ctrl-CAborts a application
Ctrl-ZSuspend a application. Resume it again by fg (resume in foreground) and bg (resume in background).
Use jobs if you have multiple suspended applications and use fg %# (where # is the job number) to get it back on screen or end it with kill %#.
Ctrl-Dis same as typing exit
Pos1like Ctrl-A
Endlike Ctrl-E
Ctrl-RSearch terminal history
Ctrl-GExit searching terminal history

Some of the shortcuts are also recognized by other applications, like Ctrl-U on Ubuntu’s graphical login screen.

Terminal

[Shell] Delete a folder and its content

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If you downloaded a series there are often folders for each episode. Each episode folder often includes another folder called “Sample” with a short demo video file.

Series -> Season 01 -> Episode 01 -> Sample -> sample.mkv

To get rid of these you can use the “find” and “rm” command. To remove each sample folder with its content you have to use the remove command with an “-r”.

find -name "Sample" -exec rm -r "{}" \;
Debian, Docker, LXC

[Docker] Install Docker in LXC running Debian Buster

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If you already have an LXC with Debian running, add the following three lines to the lxc config (path /etc/pve/lxc/xxx.conf) and reboot the container:

lxc.apparmor.profile: unconfined
lxc.cgroup.devices.allow: a
lxc.cap.drop:

Now simply install docker.

sudo apt update && apt upgrade -y
sudo apt install apt-transport-https ca-certificates curl gnupg2 software-properties-common
curl -fsSL download.docker.com/linux/debian/gpg | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian $(lsb_release -cs) stable"
sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io docker-compose

Running and managing docker containers requires sudo privileges. If you don’t want to type sudo for every commmand, add your current user to the docker group.

sudo usermod -aG docker ${USER}

Docker should now be installed, the daemon started, and the process enabled to start on boot. Check that it’s running.

sudo systemctl status docker

Test if the installtions is working correctly with hello-world. 

sudo docker run hello-world

Each container you will create gets a unique ID and name you can look up with “docker ps”. To remove the docker instance just use “docker rm” followed by the ID or the container name.

sudo docker ps -a
sudo docker stop relaxed_williamson
sudo docker rm relaxed_williamson
Terminal

[Shell] SSH Passwordless Login Using SSH Keygen

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Generate key, copy key to server and finally ssh passwordless into your server.

ssh-kegen -t rsa
ssh-copy-id root@ip
ssh root@ip

View your generated key with:

cat /home/user/.ssh/id_rsa           #local
cat /home/user/.ssh/authorized_keys  #server

To disable password authentication permanently you have to edit the ssh config. Be sure to first backup before editing. Now just set PasswordAuthentication to “no” in your config and restart the ssh daemon.

cp /etc/ssh/sshd_config /etc/ssh/sshd_config_bak
nano /etc/ssh/sshd_config
service ssh restart
Software, VirtualBox

[NFS] Mount NFS Share inside VirtualBox VM

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When receiving an error mounting an NFS share inside your VM:

sudo mount -t nfs xxx.xxx.xxx.xxx:/data/media /mnt/nfs/media
mount.nfs: access denied by server while mounting xxx.xxx.xxx.xxx:/mnt/nfs/media

Just change the network adapter of your VM in VirtualBox from “NAT” to “Bridge Mode”.

As alternative you can force the usage of the TCP protocol when mounting, like it is described here.

Manjaro, Mint, VirtualBox

[Linux Mint] Installing Manjaro KDE Plasma in VirtualBox 6.0 on Linux Mint 19.2 Cinnamon

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Install VirtualBox 6.0 on Linux Mint.

wget -q https://www.virtualbox.org/download/oracle_vbox_2016.asc -O- | sudo apt-key add -
echo "deb [arch=amd64] https://download.virtualbox.org/virtualbox/debian bionic contrib" | sudo tee /etc/apt/sources.list.d/virtualbox.list
sudo apt-get update
sudo apt-get install -y virtualbox-6.0

Download the Manjaro ISO here.
Run VirtualBox and create a new VM with type “Linux” and version “Arch Linux (64-bit)”. If done, go to Settings -> Display and switch Graphics Controller to “VBoxVGA” to be able to change the screen resolution of your VM. For transparency effects, you can also check “Enable 3D Acceleration”.
(Changing this setting didn’t work on my existing VM, only when creating a new VM. So it’s important to do this step before installing the OS.)

Now go to Storage and add your Manjaro ISO as optical drive.

Start the VM and go through the Manjaro installation process. If done, shutdown your VM, go back to settings and remove the Manjaro ISO as optical drive. Else it will boot again into the installer. Now start the VM again.

To run with the VirtualBox Guest Additions, you only have to install virtual-box-utils inside your VM:

sudo pacman -S virtualbox-guest-utils