UNIX

use tldr to get basic info on cmds

User Mgmt

gen a pw

tr -dc A-Za-z0-9_ < /dev/urandom | head -c 16 | xargs

add user:

adduser USERNAME

useradd -m USERNAME     # add and create $HOME

add user to unix group:

sudo usermod -a -G dialout m
sudo usermod -a -G sudo m

remove an user from a group:

sudo deluser $USER group

disable user

usermod -L pi

enforce password change after login

passwd -e $USER

sudo

allow user to do stuff:

michal_rudolf ALL=(ALL) NOPASSWD: /usr/sbin/tcpdump

Package Mgmt

DEB

apt-get for cygwin: http://dev.lab427.net/apt-cyg.html

dpkg -S `which mysqldump`           # show to which pkg belongs given file
dpkg -x ipp-linux_1.68.165-1_amd64.deb ipp

Upgrade to new release

check /etc/update-manager/release-upgrades for Prompt=normal

sudo apt update
sudo apt dist-upgrade
sudo do-release-upgrade -d            # -d: development release
sudo apt --fix-broken-install         # after dpkg if it fails
sudo apt --install-suggests PACKAGE

use sudo apt autoremove instead of sudo apt uninstall to get rid also of unused dependencies.

sudo apt autoclean
sudo apt clean

sudo apt install debfoster
sudo debfoster

RPM

yum provides /usr/bin/ab

sudo yum install /usr/bin/ab

yum search all <search terms>

Networking

fuser

fuser 5000/tcp              # what process is listening on a port?
sudo fuser 5000/tcp -k

show network settings:

nmcli device show

show configured dns:

nmcli dev show | grep IP4.DNS

[tcpdump]

Service Mgmt

systemctl

sudo systemctl list-units --type=service --state=enabled,disabled --state=running

sudo systemctl disable --now SERVICE

systemctl                               # list units
sudo systemctl stop redis-server        # stop an unit
systemctl status redis-server   
sudo systemctl disable redis-server

sudo update-rc.d mpd disable

ps -fu                                  # (f)ull, (u)userlist
loginctl list-users
loginctl enable-linger m

systemctl --user 
systemctl --user start mpd
systemctl --user daemon-reload          # on config change

systemctl restart rsyslog

Misc

LVM resize

lsblk
cfdisk /dev/sda         # extend, write and quit
pvresize /dev/sda3
lvresize -t -v -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv
resize2fs /dev/ubuntu-vg/ubuntu-lv

home router:

sudo ufw enable
#sudo ufw loggin on

sudo $EDITOR /etc/netplan/*yaml
sudo netplan generate
sudo netplan apply
sudo apt-get install isc-dhcp-server
sudo vi /etc/dhcp/dhcpd.conf 
sudo systemctl restart isc-dhcp-server
sudo systemctl enable isc-dhcp-server
sudo systemctl status isc-dhcp-server    
sudo vi /etc/ufw/sysctl.conf        # enable net/ipv4/ip_forward=1
# create /etc/rc.local with firewall rules -> systemctl?
    # flush it initially?

epub to pdf convert:

https://askubuntu.com/questions/299747/converting-epub-files-to-pdf-format

youtube-dl 403:

youtube-dl --rm-cache-dir

ffmepg

# Cut off first 10 seconds:
ffmepg -ss 00:00:10 -i input.file output.file

# Reduce size of mp4
ffmpeg -i input.file -vcodec libx265 -crf 30 output.file

xz -9 -T2 -v some.tar

Ubuntu

vpn

bootable usb:

https://github.com/jsamr/bootiso

fractional scaling:

# wayland
gsettings set org.gnome.mutter experimental-features "['scale-monitor-framebuffer']"

# xorg
gsettings set org.gnome.mutter experimental-features "['x11-randr-fractional-scaling']"

android remote:

 https://www.fossmint.com/scrcpy-mirror-control-android-from-ubuntu/

reconfigure gdm

sudo dpkg-reconfigure gdm3

boot logo ubuntu:

sudo update-alternatives --config default.plymouth
sudo update-initramfs -u