Monthly Archives: December 2025

dmesg

December 26, 2025Cheat Sheet, LinuxRoman

# User friendly time
dmesg --ctime

bash

December 26, 2025Cheat Sheet, LinuxRoman

#!/usr/bin/env bash

set -euo pipefail

# Get time
NOW=$(date '+%d/%m/%Y %H:%M:%S');
echo "$NOW: Text"

#!/usr/bin/env bash

set -euo pipefail

# Get time
NOW=$(date '+%d/%m/%Y %H:%M:%S');
echo "$NOW: Text"

dd

December 23, 2025Cheat SheetRoman

Backup / Clone

# clone disk
dd if=/dev/sdX of=/dev/sdY bs=64K conv=noerror,sync status=progress

# backup to file using gzip compression
dd if=/dev/sdX bs=64K conv=noerror,sync status=progress | gzip -c  > /PATH/TO/DRIVE/backup_image.img.gz

# restore from file
gunzip -c /PATH/TO/DRIVE/backup_image.img.gz | dd of=/dev/sdX status=progress

# restore from file without gzip
dd if=/PATH/TO/DRIVE/backup_image.img of=/dev/sdX status=progress

# clone only to the end of last partition
SECTOR_SIZE=$(blockdev --getss /dev/sdX)
# LAST_END=start + size - 1
sfdisk -d /dev/sdX
# parameters for dd
bs="$SECTOR_SIZE" count="$LAST_END"

Mount Image

# Scan
losetup --partscan --find --show backup_image.img

# Free-up
losetup -d /dev/loop0

Nginx

December 21, 2025Linux, NGINXRoman

Configuration

# HTTP to HTTPS
if ($scheme = http) {
    return 301 https://$host$request_uri;
}

# Proxy
location / {
    include /etc/nginx/proxy_params;
    proxy_pass http://127.0.0.1:5000/;
}

# Custom robots.txt
location = /robots.txt {
    add_header Content-Type text/plain;
    return 200 "User-agent: *\nDisallow: /\n";
}

# Activate HTTP2 (1.9.5+)
listen 443 ssl http2;

Rate limiting

# Use $http_cf_connecting_ip instead of $binary_remote_addr when behind Cloudflare
limit_req_zone $http_cf_connecting_ip zone=php_limit:10m rate=10r/s;
limit_req_log_level warn;

location ~ \.php$ {
    limit_req zone=php_limit burst=50;
}

# Test using bash
for i in $(seq 1 30); do curl -I -s "https://[HOST]/" | head -n 1; done

AutoMySQLBackup

December 20, 2025Cheat Sheet, LinuxRoman

Configuration

```
# Set rotation of daily backups. VALUE*24hours
# If you want to keep only today's backups, you could choose 1, i.e. everything older than 24hours will be removed.
CONFIG_rotation_daily=6

# Set rotation for weekly backups. VALUE*24hours
CONFIG_rotation_weekly=30

# Set rotation for monthly backups. VALUE*24hours
CONFIG_rotation_monthly=90
```

apt

December 20, 2025Cheat Sheet, LinuxRoman

CLI

# Clear package cache
apt clean

# Installed package version
apt list --installed | grep [package]

# Get versions of package
apt-cache policy [package]

Apache

December 20, 2025Apache, Cheat SheetRoman

CLI

# Enable modules
a2enmod ssl
a2enmod rewrite

# Disable autoindex
a2dismod autoindex

# Enable default SSL config
a2ensite default-ssl

Configuration

# HTTP to HTTPS
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI}

Upgrade Debian 12 to Debian 13

December 19, 2025DebianRoman

I use those steps on LXC virtual in Proxmox:

Make sure all packages are upgraded: apt update && apt upgrade
Backup container in Proxmox
Edit release version: sed -i'.bak' 's/bookworm/trixie/g' /etc/apt/sources.list
Update other configuration files in /etc/apt/sources.list.d/ appropriately
Update packages index: apt update
Do minimal system upgrade: apt upgrade --without-new-pkgs
Do full upgrade: apt full-upgrade
Restart the system: reboot