DEV Community: Zen Oh

How to Setup DNS Manager in Proxmox Using AdGuard Home

Zen Oh — Sun, 15 Feb 2026 16:39:09 +0000

First, make sure you have Ubuntu container template in Proxmox.
Create container using Ubuntu container template

Setup the Container

Do updates in container:

apt update
apt upgrade

Follow this documentation to install Docker inside your Ubuntu:
https://docs.docker.com/engine/install/ubuntu/

Remove the built in DNS service

This is the command to remove the Ubuntu built in DNS service:

Create the directory

sudo mkdir -p /etc/systemd/resolved.conf.d

Create configuration file

sudo nano /etc/systemd/resolved.conf.d/adguardhome.conf

Paste this into the file

[Resolve]
DNS=127.0.0.1
DNSStubListener=no

Create symbolic link

sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf

Restart the service

sudo systemctl reload-or-restart systemd-resolved

Run AdGuard Home

Create a directory where you want to store the docker compose file and AdGuard Home configurations, then move to that directory.

Create docker-compose.yml file:

services:
  adguardhome:
    container_name: adguardhome
    image: adguard/adguardhome
    restart: unless-stopped
    network_mode: host
    volumes:
      - ./work:/opt/adguardhome/work
      - ./conf:/opt/adguardhome/conf

Run the script:

docker compose up -d

The AdGuard Home management will run on port 3000.

Make sure you set this container as DNS server for your future VM / Container inside Proxmox that want to use this custom DNS server.

How To Change Default Screenshot Format in MacOS

Zen Oh — Wed, 17 Sep 2025 14:32:44 +0000

This is the terminal command I used to change default screenshot format to HEIC on my Mac. This is very useful to reduce the size of your screenshot.

$ defaults write com.apple.screencapture type heic
$ killall SystemUIServer

ncdu - NCurses Disk Usage

Zen Oh — Fri, 18 Jul 2025 04:45:10 +0000

If you need to find out which directories are using most storage on your mac / linux, this script is very useful.

You can install it on Mac with this command:

brew install ncdu

Here is the website of this tool:

NCurses Disk Usage

tmux Cheatsheet

Zen Oh — Wed, 09 Jul 2025 12:13:23 +0000

When you SSH into a server, sometimes you need to run a script that takes a long time to execute. You have to keep the connection open while the script is running—otherwise, it might fail (for example, if your internet connection gets disconnected).

tmux is a terminal multiplexer. It lets you switch easily between several programs in one terminal, detach them (so they keep running in the background), and reattach them later.

Here are the common commands I usually use with tmux:

New Session

tmux new -s s1

Detatch Session

Ctrl + b then d

List Session

tmux ls

Attach Session

tmux attach -t s1

Kill Session

tmux kill-session -t s1

Go to Folder: A Mac Shortcut You Need to Know

Zen Oh — Tue, 22 Oct 2024 03:19:48 +0000

Ever find yourself wishing you could instantly jump to a specific folder on your Mac without having to endlessly browse through your file system? Well, here's a handy shortcut that will save you time and effort: CMD + Shift + G.

This simple key combination opens a "Go to Folder" window, allowing you to directly input the path to your desired directory. No more clicking through countless folders!

Here's how it works:

Press CMD + Shift + G simultaneously.
A "Go to Folder" window will appear.
Type in the full path of the folder you want to access.
Press Enter.

This shortcut is a lifesaver when working with deeply nested folders or when you know the exact path to your destination. Give it a try and see how much time you can save!

How to Check Your DNSSec Configuration is Valid

Zen Oh — Fri, 18 Oct 2024 14:20:54 +0000

You can use either of these tools (I only ever use the first one):

Make sure to change example.com one with your domain.

YubiKey Setup Tutorial for macOS

Zen Oh — Mon, 14 Oct 2024 06:44:55 +0000

How to setup multiple Yubikey as smartcard login for macOS

Generate 2 certificates for 9A and 9D slot in YubiKey PIV. Here is the command to generate the certificate:

openssl ecparam -name secp256r1 -genkey -out ec_key.pem  
openssl req -new -x509 -key ec_key.pem -sha256 -nodes -out ec_crt.crt -days 10950  
openssl pkcs12 -export -out enc.p12 -inkey ec_key.pem -in ec_crt.crt

Import the p12 files to both of your YubiKeys by using YubiKey Manager App. DO NOT click setup for macos button in your YubiKey Manager because it will replace your keys.
Unplug & Replug your YubiKeys, and when this notification appear click pair & enter your login password & YubiKeys PIV PIN.

How to add smartcard only authentication in Mac

Create new .mobileconfig profile with this content (i.e. smartcard-only-login.mobileconfig):

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"\>
<plist version="1.0">
<dict>
<key>PayloadContent</key>
<array>
<dict>
<key>PayloadDescription</key>
<string>Configures smart card-only</string>
<key>PayloadDisplayName</key>
<string>Smart card-only</string>
<key>PayloadIdentifier</key>
<string>com.apple.configprofile.78.</string>
<key>PayloadOrganization</key>
<string>Apple</string>
<key>PayloadType</key>
<string>com.apple.security.smartcard</string>
<key>PayloadUUID</key>
<string>5A15247B-899C-474D-B1D7-DBD82BDE5678</string>
<key>PayloadVersion</key>
<integer>1</integer>
<key>UserPairing</key>
<false/>
<key>allowSmartCard</key>
<true/>
<key>checkCertificateTrust</key>
<false/>
<key>enforceSmartCard</key>
<true/>
</dict>
</array>
<key>PayloadDescription</key>
<string>Smartcard profile.</string>
<key>PayloadDisplayName</key>
<string>Smart card-only</string>
<key>PayloadIdentifier</key>
<string>com.apple.configprofile.77</string>
<key>PayloadOrganization</key>
<string></string>
<key>PayloadRemovalDisallowed</key>
<false/>
<key>PayloadType</key>
<string>Configuration</string>
<key>PayloadScope</key>
<string>system</string>
<key>PayloadUUID</key>
<string>7D34CC86-C707-44D2-9A9F-C5F6E347BD77</string>
<key>PayloadVersion</key>
<integer>1</integer>
</dict>
</plist>

Install by double click the created file.
Activate the profile by go to Settings - Generate - Device Management.

How to unpair YubiKey.

Make sure you have not set your Mac does not install smartcard only authentication profile.
Use this command unpair based of user:
```
sc_auth unpair -u $USER  
```

Reference:

How to use git submodule

Zen Oh — Wed, 14 Aug 2024 03:23:22 +0000

Git submodule is useful when you need another git repository inside your git project. This repository should not be library managed by dependency manager. Here is useful command I used to manage git submodule.

How to install/add new submodule to current repository

git submodule add <git repository url> <destination folder>

How setup existing submodule in cloned repository

git submodule init
git submodule update

How to update submodule

git submodule update

If you need to update the code inside of the submodule, you can just go to your submodule directory and update the code. After that point your cli to your submodule directory and do a commit & push like normal git repository. Make sure your update won't break another project that already use your submodule.

Example NFS configuration between Mac (Host) and Ubuntu VM (Client)

Zen Oh — Thu, 04 Jul 2024 06:58:58 +0000

Configure the nfs export configuration in this file for Mac with this value:

#file: /etc/exports

/<path-to-share> -mapall=501:20 192.168.1.2 192.168.1.3 192.168.1.4

501 should be your default user id in your Mac and 20 should be default group id (staff) in your Mac. The ip should be list of allowed ip to access the NFS.

Configure the nfs mount configuration in this file for Ubuntu with this value:

#file: /etc/fstab

<host-ip>:/<path-to-share>    /<path-to-mount>    nfs    rw,tcp,nolock,noacl,async    0 0

Make sure you have created a directory for /.

How to Expand Ubuntu Drive

Zen Oh — Thu, 04 Jul 2024 03:16:24 +0000

When you are using vmware to create Ubuntu Server VM, it will only use half of the assigned hard drive storage if you are not changing it in the installation process. Here is how to resize it.

root@util:~# vgdisplay
<snip>
root@util:~# lvextend -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv
<snip>
root@util:~# resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv
<snip>

This method still works in Ubuntu 24.04 as of today (2024-07-04)

Reference:

Partition, format, and mount a drive on Ubuntu

Zen Oh — Mon, 24 Jun 2024 03:13:49 +0000

Reference:

https://www.howtogeek.com/106873/how-to-use-fdisk-to-manage-partitions-on-linux/

List logical disks and partitions

sudo fdisk -l

Partition the disk

sudo fdisk /dev/sdb

Press n to create a partition
Press p or l to create primary or logical partitions
Press w to write your changes or q to quit

Format the partition

sudo mkfs -t ext4 /dev/sdb1
sudo mkfs -t ext4 -N 2000000 /dev/sdb1 - This will manually set the number of inodes to 2,000,000

Mount disk

mount - Shows what is mounted
mkdir /mnt/mydrive
mount -t ext4 /dev/sdb1 /mnt/mydrive

Get disk's UUID

ls -al /dev/disk/by-uuid/

or

blkid

Mount at boot

Add the following line to your /etc/fstab file adjusting the UUID to your device's id and the directory to where you want to mount:

UUID=811d3de0-ca6b-4b61-9445-af2e306d9999 /mnt/mydrive ext4 defaults 0 0

mount -a - remounts filesystems from /etc/fstab

How To Setup 1Password SSH For Windows

Zen Oh — Fri, 14 Apr 2023 07:57:04 +0000

Here is 3 articles useful for setting up 1Password SSH for Windows, WSL, and WinSCP Support via WinSSH-Pageant:

The location of winssh-pageant installation when using winget is:

%userprofile%\AppData\Local\Programs\WinSSH-Pageant\winssh-pageant.exe