Playing with Alpine VM

Sat Nov 12 2022

Virtualization

Alpine

Let’s say you need to play/learn virtualization on linux but you are system has pretty low specs then what would you do ? we would use a low foot print linux distro, I choosed Alpine

Before we start, we need to download the alpine iso, Alpine offers wide variety of iso. you can download the iso from

https://alpinelinux.org/downloads/ I choose virtual(x86_64) and it is only 50MB (Mind Blown).

Okay let’s boot up Virtual Box and Create a new VM Type : Linux Version: Other Linux(64 Bit) no other special option, just go with default option.

Before booting the server, let’s set the networking.

Networking

We need to forward the SSH port to Host so that we can connect to SSH using NAT.
Right click the VM and choose the settigs.
Navigate to the Network tab.
Click the Advanced and Tap the Port Forwarding button
Add new Rule
- Name: SSH
- Protocol: TCP
- Host Protocol: 2200
- Guest Protocol: 22
Add another Rule
- Name: Test
- Protocol: TCP
- Host Protocol: 4444
- Guest Protocol: 4444
Just leave the host and guest IP address as blank.

Booting

Start the VM
When asked for username enter root

Setting up network

By default all the network interface are down
You can check the network interface using

ifconfig -a

To up the network interface

ifconfig lo up
ifconfig eth0 up

Get IP address automatically

vi /etc/network/interfaces
iface eth0 inet dhcp

up the eth0

ifup eth0

Now check if you have ip address in eth0.

Checking network connection

To check Host and Guest network connection works properly.
We will use a tool called nc (netcat).
In Alpine enter

nc -l -p 4444

In Host system enter

nc localhost 4444

if you type in guest/host, the text will appear in other system.
If that happens then network connection is configured properly.

Setting up SSH Server

Install openssh server in alpine

apk add openssh

Enable the sshd service so that its starts at boot

rc-update add sshd

List services using

rc-status

To check the sshd is enabled or not.
Before we start let us disable the password authentication for SSH.

vi /etc/ssh/sshd_config

Search for the following string and remove # before and set yes to no.

PasswordAuthentication no

Start sshd service

/etc/init.d/sshd start

SSH Connection between Guest and Host

In Host system we need to run

ssh-keygen

Will use default file name and no passpharse
This will create a id_rsa and id_rsa.pub file
We need to copy the file id_rsa.pub to the Alpine VM
We can use the nc.

nc -l -p 4444 > ~/.ssh/authorized_keys # On VM
nc localhost 4444 < ~/.ssh/id_rsa.pub # On Host

After few seconds we can cut the connection using Ctrl+c.
Ensure the permission of the ssh related files and folder

chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

Restart the SSH server

/etc/init.d/sshd restart

Connect from Host

ssh -i ~/.ssh/id_rsa.pub root@localhost -p 2200

Voila you logged into Alpine VM from Host system.

The VM is created for demo purpose if you are using it for real projects, read below heading

Do’s and Don’t

Use passpharse when generating ssh-keygen.
Use ssh-copy-id instead of nc

ssh-copy-id -i path/to/certificate -p port username@remote_host

In next article we can look into how to communicate between two Alpine VM.