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  * **miscadmin** 
  * **Jonathan Haack**
  * **Haack's Networking**
  * **netcmnd@jonathanhaack.com** 

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A dumping ground for basic gnulinux sysadmin and other miscellaneous notes, or //miscadmin// for short.

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-Text Editors-

Change the default text editor, terminal, web browser, in Debian

  exo-preferred-applications

Some systems are not kind with exo, so ...

  xdg-mime default caja.desktop inode/directory application/x-gnome-saved-search
  
Set caja or other file managers to manage desktop

  gsettings set org.gnome.desktop.background show-desktop-icons false
  gsettings set org.nemo.desktop show-desktop-icons true

-motd-

Create the following to make a message of the day that will be appended to the dynamic message of the day.

  sudo nano /etc/motd

Is motd printing twice, comment out motd statis in pam setting

  /etc/pam.d/sshd
  #session    optional     pam_motd.so noupdate
  (actually it is the line above this, leave this active)
  
Print motd with every shell log in ...

  nano ~/.bashrc
  
Navigate to the end of the file, and add
  
  cat /etc/motd
 
-Firefox-

To install the latest firefox on Debian and make it default, do the following.  The link below may not always work, so replace when updated.

  sudo mkdir -p /opt/firefox
  sudo chown -R $USER:$USER /opt/firefox
  cd ~/Downloads && wget -O FirefoxSetup.tar.bz2 "https://download.mozilla.org/?product=firefox-latest&os=linux64&lang=en-US"
  tar xjf FirefoxSetup.tar.bz2 -C /opt/firefox/
  sudo mv /usr/lib/firefox-esr/firefox-esr /usr/lib/firefox-esr/firefox-esr_orig
  sudo ln -s /opt/firefox/firefox/firefox /usr/lib/firefox-esr/firefox-esr

To restore firefox-esr that comes with Debian.

  unlink /usr/lib/firefox-esr/firefox-esr
  mv /usr/lib/firefox-esr/firefox-esr_orig /usr/lib/firefox-esr/firefox-esr
  
-youtube-dl-

  sudo curl -L https://yt-dl.org/downloads/latest/youtube-dl -o /usr/local/bin/youtube-dl
  sudo chmod 750 /usr/local/bin/youtube-dl

-optical ripping example-

  cdrecord -pad -dao -data blag-140k-i686.iso

-pam hardening location-

  sudo nano /etc/pam.d/common-password

Prevent Log in - create file

  /etc/nologin

-old reminders-

remove old and offending keyring from gnome, make new directory for new one

  sudo rm -rf ~/.local/share/keyrings
  mkdir ~/.local/share/keyrings

start or stop network manager (or other services)
  
  systemctl <start/stop/restart> networkmanager.service
  /etc/init.d/network-manager <start/stop/restart>
  
verify dhcp client working for interface eno1
  
  dhclient -v eno1
  
add subnet to interface eno1
  
  ip address add 192.1##.1##.2/24 dev eno1
  
interface tool w/ eno1 example
  
  ethtool eno1  

interface with switch using screen
  
  screen /dev/ttyUSB0/ 19200

calculate subnet automatically
  
  subnetcalc
  
proxying web traffic through remote server 
  
  ssh -D <port#> <user>@<domain.com>
  
get block ID of drives
  
  blkid

nmap to scan devices on lan
  
  nmap -sP 10.##.##.0/24

find utils example

  find . -iname "name" 
 

-ngrok-

ngrok notes; private http(s) tunnels

  ./ngrok http 80
  wget https://[ngrok tunnel]/id_rsa.pub
  cat ~/id_rsa.pub >> ~/.ssh/authorized_keys

query hosts on the lan

  avahi-browse -tl _workstation._tcp

Debian print system configuration to stdout; use root

  cat /proc/cpuinfo && lspci | grep -i vga && uname -a && lsb_release -a
  lsb_release -a
  lspci

Debian repo management

  cd /etc/apt
  nano sources.lsit
  [main contrib non-free]
  
  
-sftp basics-

  cd ~/Downloads
  sftp user@host.com:/path/to/sftp/directory/of/choice/
  > put /path/to/file.txt 
  
  
-build app from source-

tar -xf <source_filename>

Navigate to the directory that tar unarchived the files to.  Then, within that directory, execute:

  ./configure --prefix=/usr/local
  
  make
  sudo make install clean


-using vi to scrape unnecessary text strings away from openwrt packages that need updating

  :1,$s/ .*//


-passing traffic through wifi radio to another interface on host-

  sudo su -c "iptables -t nat -A POSTROUTING -o wlp2s0 -j MASQUERADE"
  sudo su -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

  set a static ip using ip a a x.x.x.x. dev blah

  set static on wndr wan

-exim delete all messages and other-
  
  exim -bp <print message ids>
  exim -Mrm <message id>
  exim -bp | awk '/^ *[0-9]+[mhd]/{print "exim -Mrm " $3}' | bash
  
  use this for local interfaces for ipv6
  ::::0:0.0.0.0
  
  view
  exim -Mvh
  
-verifying TLS with swaks on exim4 relay setup

  swaks -a -tls -q HELO -s smtp.haacksnetworking.com:587 -au test -ap '<>'
  
-mysql password-

  nano /etc/mysql/debian.cnf 
  sudo mysql -u debian-sys-maint  
  
-temporary name servers - how to add some - temporary/permanent syntax below:

  echo "nameserver 4.2.2.1" | sudo tee /etc/resolv.conf > /dev/null
  echo "nameserver 4.2.2.1" | sudo tee /etc/resolvconf/resolv.conf.d/base > /dev/null
  
-strip desktop environments from GUI system
  
  tasksel --list-tasks
  tasksel --task-packages desktop
  sudo apt-get purge $(tasksel --task-packages desktop)

-deborphan

  sudo apt install deborphan
  sudo apt-get remove `deborphan`
  for i in `deborphan`; do apt-get --purge remove -y $i; done

-checking ssh logs

  cat /var/log/auth.log | grep 'sshd.*Invalid'
  cat /var/log/auth.log | grep 'sshd.*opened'
  
-checking disk space-

  du -ch -d 1 | sort -hr

-check disk space with ncurses tool-

  sudo apt install ncdu
  ncdu
  
-stop/start sleep of any form on servers-

  sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target
  sudo systemctl unmask sleep.target suspend.target hibernate.target hybrid-sleep.target
  
-xorg with ssh

  touch /root/.Xauthority 
  touch /home/user/.Xauthority
  
-batch convert with ffmpeg to mp4 from mkv

  for i in *.mkv; do
  ffmpeg -i "$i" -codec copy "${i%.*}.mp4"
  done

-fix badly configured zpool that used short names to by-id names. This command can be entered as-is, and does not need to be adjusted at all for what your specific ids are or for multiple drives. It literally exports the short names and by-ids, unmounts the volumes/pool, then remakes it using the blkid.

  zpool export tank 
  zpool import -d /dev/disk/by-id tank
  
monitor ram usage every 3 seconds in human readable way

  free -h -w -s 3
  
postfix to relay, satellite option, enter the relay like this:  to prevent lookups
  
  [smtp.smtpserver.com]:587
  
Re-attach to screen session that's attached.

  screen -d -r <session#.user>
  
mysqldump to local from remote

  ssh root@hub.haacksnetworking.org /usr/bin/mysqldump --all-databases --single-transaction --skip-comments --skip-dump-date > hknet.sqldump
  
Turn off sleep.

  sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target
  
Amd gPU errors fix
  
  mkdir ~/Repositories
  cd /home/user/Repositories && git clone https://kernel.googlesource.com/pub/scm/linux/kernel/git/firmware/linux-firmware.git
  sudo cp /home/user/Repositories/linux-firmware/amdgpu/* /lib/firmware/amdgpu && sudo update-initramfs -k all -u -v
  
Unattended Upgrades

  sudo apt install unattended-upgrades
  sudo apt install apt-config-auto-update
  sudo unattended-upgrades --dry-run --debug
  sudo systemctl status unattended-upgrades

Next ... ssh failed attempts

  grep "Failed password" /var/log/auth.log
  journalctl _SYSTEMD_UNIT=ssh.service | egrep "Failed|Failure"
  faillock --user <user>
  grep "authentication failure" /var/log/auth.log | awk '{ print $14 }' | cut -b7-  | sort | uniq -c

Display Managers (Lightdm, etc.)

  sudo nano /etc/lightdm/lightdm-gtk-greeter.conf
  [SeatDefaults]
  allow-guest=false
  greeter-hide-users=true
  nano ~/.config/gtk-3.0/settings.ini
  [Settings]
  gtk-application-prefer-dark-theme=1
  sudo nano /etc/lightdm/lightdm.conf
  cd /usr/share/lightdm/light.conf.d/
  
Setting ufw to allow connections to only certain subnets.

  ufw allow from 192.168.1.0/24 to any proto tcp port 8006
  
 --- //[[jonathan@haacksnetworking.org|oemb1905]] 2024/01/28 20:31//
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