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Restoring SSH on the misconfigured Linux system
Currently working as a Senior Consultant at Netcompany spending my full-time job solving the SharePoint riddles. In the free time I'm expanding my understanding of cybersecurity through hacking activities. Git fanboy.
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Yeah, so the story is short. I was trying to restore IPv4 SSH configuration so I've changed a sshd_config from
Port 12345
AddressFamily inet6
#ListenAddress 0.0.0.0
#ListenAddress ::
to
Port 12345
AddressFamily inet4
#ListenAddress 0.0.0.0
#ListenAddress ::
And restarted the system (because for some reason, simple sudo systemctl restart ssh didn't work).
And after my Pi rebooted
I couldn't access my system.
For those who don't know yet, what did I wrong… Let me share something
I typed AddressFamily inet4 instead AddressFamily inet. Yet another example where Linux basically allows you to do anything you want.
("Source": https://9gag.com/gag/abVPE5O)
Because I didn't brick the system and all I need is to change that line in the sshd_config - solution was simple. Mount that SD card in another Linux system and edit file.
Problem was that my main and only bare-metal system is Windows. So, I had to mount SD card on the guest Linux OS on a Windows host. Here is how
To be able to see the SD card on the Linux inside VirtualBox you have to prepare VMDK (Virtual Machine Disk) file linked to the device.
You have to repeat these steps each time device is inserted in USB. Windows will assign it the new
PHYSICALDRIVEnumber.
wmic diskdrive list brief
DeviceID - in my example, it is \\.\PHYSICALDRIVE3..\VBoxManage.exe internalcommands createrawvmdk -filename D:\ETH\pi.vmdk -rawdisk \\.\PHYSICALDRIVE3
If you have changed the VMDK file (ex. generated once again for new
PHYSICALDRIVE) that is already imported in VirtualBox, you have to remove it and add again (in File -> Virtual Media Manager...). Otherwise machine with attached VMDK won't run.
sudo fdisk -l
sudo mkdir /mount/external-sd
sudo mount /dev/sdb2 /media/external-sd
Don't mount whole device as
mount /dev/sdb .... Use only the partition that is not marked as boot (or more accuratly, mount Linux partition)
/media/external-sdsudo umount /media/external-sd
$ sudo mount /dev/sdb2 /media/external-sd
After all that wasn't so problematic this time, becasue I had to modify back single line in SSH config. ..but now I have a second SD card with system that got closed abruptly during the updates. Now all my login tries got rejected 😅