DEV Community: Mohammad Javad Naderi

Accessing Host Services from Docker Containers

Mohammad Javad Naderi — Sun, 18 Feb 2024 22:25:25 +0000

Accessing a host service from within a Docker container is a common requirement. For instance, you might have a HTTP proxy running on the host system at 127.0.0.1:8080 that you want to access from a Docker container.

One straightforward solution is to use --network host for the Docker container or network_mode: host in Docker Compose. However, this approach can lead to complications. If you use network_mode: host for one service, you may find yourself needing to use it for other services or publish their ports just to enable them to communicate with each other. This can quickly result in losing the benefits of Docker Compose's default network.

A more elegant solution is to connect to the special DNS name host.docker.internal, which resolves to the internal IP address used by the host (for example, using host.docker.internal:8080 to connect to the proxy). On Linux, you need to pass --add-host=host.docker.internal:host-gateway to the docker command. The Docker Compose equivalent is:



extra_hosts:
  - host.docker.internal:host-gateway

However, this method won't work, since our host service is listening on 127.0.0.1. One workaround is to bind the host service to 0.0.0.0, but this exposes it to the outside world, which is often undesirable. The other workaround is to bind the host service to 172.17.0.1, but other apps that rely on 127.0.0.1:8080 will break. Or we can bind to both 127.0.0.1 and 172.17.0.1, but the host service may have no configuration option to specify the address or bind to multiple addresses.

Solution using Socat

I found a simple and effective solution to this problem using the socat command. Socat is a command-line utility that establishes two bidirectional byte streams and transfers data between them. In this context, it can be used to listen on a TCP port on host.docker.internal and forward to the host service. This allows you to connect to the host service using host.docker.internal.

Here's how to set this up in Docker Compose for our HTTP proxy example:



services:
  proxy-relay:
    image: alpine/socat:latest
    network_mode: host
    command: TCP-LISTEN:8080,fork,bind=host.docker.internal TCP-CONNECT:127.0.0.1:8080
    extra_hosts:
      - host.docker.internal:host-gateway

  my-service:
    image: some-image
    command: my-command --connect-to host.docker.internal:8080
    extra_hosts:
      - host.docker.internal:host-gateway

In this configuration, the proxy-relay service listens on host.docker.internal:8080 and forwards to 127.0.0.1:8080. This allows my-service to access the proxy without using network_mode: host and without changing the bind address of the proxy. We also did not hard-code 172.17.0.1 anywhere.

Did you find this post useful? Please leave your feedback in the comments. 😊️

Installing Arch Linux with Full Disk Encryption

Mohammad Javad Naderi — Wed, 27 Sep 2023 09:43:02 +0000

If you're aiming for a seamless encrypted Arch Linux installation in UEFI mode, follow along as this guide will walk you through the process step by step. We'll be using LUKS (Linux Unified Key Setup) and LVM (Logical Volume Manager) partitions on LUKS to achieve full disk encryption.

For your convenience, you can also find this guide as a GitHub Gist.

If you're only interested in installing Linux and not setting up dual boot with Windows, feel free to skip the Windows-related sections.

Prepare the System

Before we dive into the installation process, let's ensure that your system is ready:

Data Backup: Make sure you've backed up all your important data. We're about to make significant changes, and it's always wise to have a safety net.
UEFI Mode: In your system's BIOS settings, set the boot mode to UEFI.

Prepare the USB Drive

Ventoy Installation: Start by installing Ventoy on your USB drive. Ventoy is a versatile tool that allows you to easily create a multi-boot USB drive.
Download Arch ISO: Head to Arch Linux's official website and download the Arch ISO image. Copy it to your USB drive.
Optional Windows 11: If you plan to set up a dual boot with Windows 11, download the Windows 11 ISO image and also copy it to your USB drive.

Disk Partition Structure

Here is an example to give you a clear picture of what the final disk partition structure will look like. If you're not interested in installing Windows, you can simply ignore the green parts.

For better flexibility, I do not reuse the Windows EFI for Linux. Instead, I create a distinct EFI partition dedicated solely to Linux, resulting in the presence of two EFI partitions. I also use separate partitions for EFI and Boot.

In the context of this guide, I've designated the disk device and Linux partitions with names according to the table below. Please be aware that these names should be substituted with the actual device paths relevant to your system configuration:

Device	In this Doc	Examples
Disk Device	`/dev/<your-disk>`	`/dev/sda`, `/dev/nvme0n1`
EFI Partition	`/dev/<your-disk-efi>`	`/dev/sda5`, `/dev/nvme0n1p5`
Boot Partition	`/dev/<your-disk-boot>`	`/dev/sda6`, `/dev/nvme0n1p6`
LUKS Partition	`/dev/<your-disk-luks>`	`/dev/sda7`, `/dev/nvme0n1p7`

Install Windows (Optional)

Boot from the Windows 11 ISO and install Windows. If you want to use BitLocker for disk encryption, ensure that you install the Windows Pro version.
In Windows, open the start menu and search for "BitLocker". Open the BitLocker settings and enable BitLocker for the C drive.
Important: Store the BitLocker recovery key in a safe place. You will need it later.

Install Arch Linux

Connect the USB drive and boot from the Arch Linux ISO.
Make sure the system is booted in UEFI mode. The following command should display the directory contents without error.
```
# ls /sys/firmware/efi/efivars
```
Connect to the internet. A wired connection is preferred since it's easier to connect. More info

Run fdisk to create Linux partitions.

# fdisk /dev/<your-disk>

If you have installed Windows, you already have a GPT partition table. Otherwise, create an empty GPT partition table using the g command. (WARNING: This will erase the entire disk.)

# WARNING: This will erase the entire disk.

Command (m for help): g
Created a new GPT disklabel (GUID: ...).

Create the EFI partition (/dev/<your-disk-efi>):

Command (m for help): n
Partition number: <Press Enter>
First sector: <Press Enter>
Last sector, +/-sectors or +/-size{K,M,G,T,P}: +100M

Command (m for help): t
Partition type or alias (type L to list all): uefi

Create the Boot partition (/dev/<your-disk-boot>):

Command (m for help): n
Partition number: <Press Enter>
First sector: <Press Enter>
Last sector, +/-sectors or +/-size{K,M,G,T,P}: +512M

Command (m for help): t
Partition type or alias (type L to list all): linux

Create the LUKS partition (/dev/<your-disk-luks>):

Command (m for help): n
Partition number: <Press Enter>
First sector: <Press Enter>
Last sector, +/-sectors or +/-size{K,M,G,T,P}: <Press Enter>

Command (m for help): t
Partition type or alias (type L to list all): linux

Print the partition table using the p command and check that everything is OK:

Command (m for help): p

Write changes to the disk using the w command. (Make sure you know what you're doing before running this command).

Command (m for help): w

Format the EFI and Boot Partitions.

mkfs.fat -F 32 /dev/<your-disk-efi>
mkfs.ext4 /dev/<your-disk-boot>

Set up the encrypted partition. You can choose any other name instead of cryptlvm.

# cryptsetup --use-random luksFormat /dev/<your-disk-luks>
# cryptsetup luksOpen /dev/<your-disk-luks> cryptlvm

Create an LVM volume group. You can choose any other name instead of vg0.
```
# pvcreate /dev/mapper/cryptlvm
# vgcreate vg0 /dev/mapper/cryptlvm
```
Create LVM partitions (logical volumes).

We create logical volumes for swap, root (/), and home (/home). Leave 256MiB of free space in the volume group because the e2scrub command requires the LVM volume group to have at least 256MiB of unallocated space to dedicate to the snapshot.
```
# lvcreate --size 8G vg0 --name swap
# lvcreate --size 100G vg0 --name root
# lvcreate -l +100%FREE vg0 --name home
# vreduce --size -256M vg0/home
```

Format logical volumes.

# mkswap /dev/vg0/swap
# mkfs.ext4 /dev/vg0/root
# mkfs.ext4 /dev/vg0/home

Mount new filesystems.

# mount /dev/vg0/root /mnt
# mount --mkdir /dev/<your-disk-efi> /mnt/efi
# mount --mkdir /dev/<your-disk-boot> /mnt/boot
# mount --mkdir /dev/vg0/home /mnt/home
# swapon /dev/vg0/swap

Install the base system. We also install some useful packages like git, vim, and sudo.
```
# pacstrap -K /mnt base linux linux-firmware openssh git vim sudo
```
Generate /etc/fstab. This file can be used to define how disk partitions, various other block devices, or remote filesystems should be mounted into the filesystem.
```
# genfstab -U /mnt >> /mnt/etc/fstab
```
Enter the new system.
```
# arch-chroot /mnt /bin/bash
```

Set TimeZone.

---> See available timezones:
# ls /usr/share/zoneinfo/

---> Set timezone:
# ln -s /usr/share/zoneinfo/Asia/Tehran /etc/localtime

Run hwclock(8) to generate /etc/adjtime.
```
# hwclock --systohc
```

Set Locale.

# vim /etc/locale.gen (uncomment en_US.UTF-8 UTF-8)
# locale-gen
# echo LANG=en_US.UTF-8 > /etc/locale.conf

Set hostname.
```
# echo yourhostname > /etc/hostname
```

Create a user.

# useradd -m -G wheel --shell /bin/bash yourusername
# passwd yourusername
# visudo
---> Uncomment "%wheel ALL=(ALL) ALL"

Configure mkinitcpio with modules needed to create the initramfs image.

# pacman -S lvm2
# vim /etc/mkinitcpio.conf
---> Add 'encrypt' and 'lvm2' to HOOKS before 'filesystems'

Recreate the initramfs image:

# mkinitcpio -P

Setup GRUB.

# pacman -S grub efibootmgr
# grub-install --target=x86_64-efi --efi-directory=/efi --bootloader-id=GRUB

In /etc/default/grub edit the line GRUB_CMDLINE_LINUX as follows. Don't forget to replace /dev/<your-disk-luks> with the appropriate path.

GRUB_CMDLINE_LINUX="cryptdevice=/dev/<your-disk-luks>:cryptlvm root=/dev/vg0/root"

If you have installed Windows and want to add Windows to the GRUB menu, edit /etc/grub.d/40_custom:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
if [ "${grub_platform}" == "efi" ]; then
  menuentry "Windows 11" {
    insmod part_gpt
    insmod fat
    insmod search_fs_uuid
    insmod chain

    # After --set=root, add the Windows EFI partition's UUID.
    # (can be found with "blkid" command)
    search --fs-uuid --set=root $FS_UUID
    chainloader /EFI/Boot/bootx64.efi
  }
fi

In the above script, replace $FS_UUID with Windows EFI partition UUID. You can find this UUID using lsblk command. It should be something like 8E12-69DD.

Now generate the main GRUB configuration file:

# grub-mkconfig -o /boot/grub/grub.cfg

Install networkmanager package and enable NetworkManager service to ensure you have Internet connectivity after rebooting.
```
# pacman -S networkmanager
# systemctl enable NetworkManager
```
Exit new system and unmount all filesystems.
```
# exit
# umount -R /mnt
# swapoff -a
```
Arch is now installed 🎉. Reboot.
```
# reboot
```
Open BIOS settings and set GRUB as first boot priority. Save and exit BIOS settings.
After booting the system, you should see the GRUB menu.

If you have installed Windows, select "Windows 11" in GRUB menu. If you have previously enabled Bitlocker, BitLocker will ask for your recovery key when you try to boot Windows through GRUB for the first time. Enter your BitLocker recovery key.
Reboot again and log in to Arch linux with your username and password.
Check internet connectivity.
```
$ ping google.com
```
If you want to use Gnome desktop, install gnome and gdm packages:
```
$ sudo pacman -S gnome gdm
```
And enable gdm service:
```
$ sudo systemctl enable gdm
```
Reboot!

Notes

Backup LUKS Header

It is important to make a backup of LUKS header so that you can access your data in case of emergency (if your LUKS header somehow gets damaged).

Create a backup file:

# cryptsetup luksHeaderBackup /dev/<your-disk-luks> --header-backup-file luks-header-backup-$(date -I)

Store the backup file in a safe place, such as a USB drive. If something bad happens, you can restore the backup header:

# cryptsetup luksHeaderRestore /dev/<your-disk-luks> --header-backup-file /path/to/backup_header_file

Disable Windows Hibernate and Fast Startup

If you want to use the same NTFS drive in both Windows and Linux (for example an NTFS partition on your internal disk or external hard drive), consider disabling "Hibernate" and "Fast Startup" features in Windows.

You can check the current settings on Control Panel > Hardware and Sound > Power Options > System Setting > Choose what the power buttons do. The box Turn on fast startup should either be disabled or missing.

More info