Upgrade Debian 10 to Debian 11

Debian

I use those steps on LXC virtual in Proxmox:

  1. Make sure all packages are upgraded: apt update && apt upgrade
  2. Backup container in Proxmox
  3. Edit release version: sed -i'.bak' 's/buster/bullseye/g' /etc/apt/sources.list
  4. Fix security distribution name: sed -i 's|bullseye/updates|bullseye-security|g' /etc/apt/sources.list
  5. Update other configuration files in /etc/apt/sources.list.d/ appropriately
  6. Update packages index: apt update
  7. Do minimal system upgrade: apt upgrade --without-new-pkgs
  8. Do full upgrade: apt full-upgrade
  9. Restart the system: reboot

tar

Cheat Sheet, Linux

Backup

See Ubuntu Help for details.

# Full root file system backup
tar -cvpzf backup.tar.gz --exclude=/backup.tar.gz --one-file-system /

# Backup remote file system (SSH)
ssh root@srv.local -p 22 "tar -cvpz --one-file-system /" > srv-backup.tar.gz

# Restore
tar -xvpzf /path/to/backup.tar.gz -C /media/whatever --numeric-owner

Other useful commands

# Remove compression from tar.gz
gzip -dk archive.tar.gz

# Compress directory
tar -zcvf myfolder.tar.gz myfolder

# Read gzipped log
zcat error.log.2.gz

Logoff desktop shortcut for all users on Windows Server

PowerShell 
$WshShell = New-Object -comObject WScript.Shell
$Shortcut = $WshShell.CreateShortcut("$env:PUBLIC\Desktop\Logoff.lnk")
$Shortcut.TargetPath = "C:\Windows\System32\shutdown.exe"
$Shortcut.Arguments = "/l"
$Shortcut.IconLocation = "C:\Windows\System32\shell32.dll,44"
$Shortcut.Save()

ImageMagic

Cheat Sheet 
# Image from PDF
convert -density 300 -rotate 90 -compress lossless input.pdf[0] output.jpg

# Icon from multiple images
convert image1.png image2.png image3.png favicon.ico

# Create favicon.ico with multiple sizes
convert favicon.png -define icon:auto-resize=96,64,48,32,16 favicon.ico

postfix

Cheat Sheet 
# Show current mail queue
mailq

# Send messages in queue
postqueue -f

# Delete message from queue
postsuper -d MSGID

# Print message from queue
postcat -q MSGID

# Show mail statistics
cat /var/log/mail.log | pflogsumm

# Rebuild aliases
newaliases

journalctl

Cheat Sheet 
# Follow postfix mail log with 40 records loaded on start
journalctl -f -u postfix@-.service -n 40

# Get one day old records
journalctl -u postfix@-.service --since "1 days ago"

# Get first 100 records since
journalctl --since "2026-03-27 07:00:00" --no-pager | head -100

du

Cheat Sheet 
# Find files / directories bigger than 1GB
du -a --threshold=1G ./

# Top 20 directories by size
du -a / --exclude=/proc --exclude=/sys --exclude=/dev --exclude=/lost+found | sort -n -r | head -n 20

# Get directory size recursively
du -hs ./

patch

Cheat Sheet 
# Create patch for file
diff -Naur original_file modified_file > changes.patch

# Test
patch --dry-run file_to_be_patched changes.patch