virsh ssh into a guest vm

Question

Is there anyway that I can ssh into a guest vm through virsh instead of find the ip address of the guest vm?

e.g.

what I want is ssh into a guest like this way :

$virsh ssh_or_somwthing <domain>

but not like this:

$ #1) find the guest vm's IP address:
$arp
...
$ #2) ssh someone@<IP>

Answer 1

Jacek has the right answer, but just to lay out some of the specifics:

1. Log into the VM using the KVM GUI

2. On the VM command line, type in:

   systemctl enable serial-getty@ttyS0.service
   systemctl start serial-getty@ttyS0.service
   

You will be asked multiple times to enter your password/accept.

3. Reboot the VM

4. Then, from the terminal on your main machine, type in:

   sudo virsh console your_vm_name_here
   

Obviously replacing "your_vm_name_here" with whatever the VM name is.

Then you can "ssh" directly into the VM using virsh.

Answer 2

virsh itself does not supply ssh capabilities in managing the VMs*.

If we want to access the machine through ssh, we may only do that through the ssh command.

Following are the 2 steps for that.

1. Setting Up the SSH Access

For the first step there are 2 tracks

Pre-Configure the Machine (eg: Cloud-Init)

We could use cloud-init (may be also preseed.cfg/kickstart ... etc.) to install the public key.

# Cloud-init snippet
users:
  - name: your_username
    ssh-authorized-keys:
      - your_public_ssh_key

Manual Configuration

1. Ensure that ssh daemon is running in the VM, if you have an interactive access, you could run virsh console $vm_name then set up the ssh daemon. If there's no interactive access you'll need to use any of the following:

   • virt-customize while the machine is shut off virt-customize -d "$vm_name" --run-command "command to install ssh"
     or
   • expect to send keystrokes to setup the VM, which could be found in the appendix of this answer.
     or
   • any other tool that sends keystrokes to the VM

2. Install your public key into the VM:

   # virt-copy-in requires the virtual machine to be stopped
   #   for example this should return `shut off`
   virsh dominfo my_vm | grep State | awk -F':' '{print $2}' | sed 's/^[[:space:]]*//; s/[[:space:]]*$//'
   # virt-copy-in takes a file argument and a directory argument
   # thus we need to use a correct filename before copying
   if [ ! -f ~/.ssh/id_rsa ]; then
       ssh-keygen -t rsa -N "" -f ~/.ssh/id_rsa
   fi
   cp ~/.ssh/id_rsa.pub /tmp/authorized_keys
   # Finally, virt-copy-in may require sudo
   virt-copy-in -d "$vm_name" /tmp/authorized_keys /home/ubuntu/.ssh/
   

2. Accessing the VM

1. Capture the IP address:

   export vm_ip_address=$(virsh domifaddr my_vm | awk '/ipv4/ {print $4}' | awk -F'/' '{print $1}')
   

2. ssh into the machine

   export vm_user=ubuntu # set the correct username here
   ssh $vm_user@$vm_ip_address
   

* virsh could use ssh to communicate with remote servers, but that has nothing to do with accessing the virtual machines themselves.

Appendix

Following is an expect snippet that could be used to automate setting up the interactive console access in a non-interactive manner.

#!/usr/bin/expect -f

Function to wait for a specific string before sending the command
proc wait_for_prompt { } {
expect "# "   ; # Modify the expected prompt if needed
}
Function to send a command and wait for the output
proc send_command { command } {
send "$command\r"
expect "# "   ; # Modify the expected prompt if needed
}
Replace 'vm_name' with the actual name of your virtual machine
set vm_name "my_vm"
Replace 'your_command' with the command you want to run inside the VM
set command_to_run1 "sudo apt-get install openssh-server."
set command_to_run2 "sudo systemctl start ssh"
set command_to_run3 "sudo systemctl enable ssh"
#spawn virsh start $vm_name
Spawn the virsh command
spawn virsh
Wait for the virsh prompt
expect "virsh # "
Start the virtual machine
send "start $vm_name\r"
send "console $vm_name\r"
Wait for the console to start
Send double enters
send_command ""
send_command ""
expect -timeout 100 "ubuntu login"
Set password
send_command "ubuntu"
send_command "ubuntu"
we may need to login again if prompted
send_command "ubuntu"
send_command "ubuntu"
run the commands
send_command "$command_to_run1"
send_command "$command_to_run2"
send_command "$command_to_run3"
Wait for the output of the command to appear
expect "your_expected_output" ; # Modify this line to match the expected output
Exit the console
send "\x1d"
expect eof

Answer 3

I'm not sure about it, but I think you're looking to configure console access to the guest? It may not be the only solution (not following virsh very actively and all this stuff) - but you can setup serial console on your guest, configure your supervisor and then use virsh console domain.

Anyway - have a look at this: https://help.ubuntu.com/community/KVM/Access - I guess it may help or at least put you in some direction.

Answer 4

You may want to take a read of SSHsetup for libvirtd

https://wiki.libvirt.org/page/SSHSetup

Seems to do what you want.

Answer 5

If you don't need to do so over and over again, one way is to use the viewer like so:

host$ virt-viewer my_vm

Then you get access to the normal Linux console or X-Windows. You can then log in and in X-Windows start a terminal and type something like:

guest$ ip address

Once done with the viewer, you can just close that window. It won't hurt the VM, it just hides the console.

This is, of course, not practical since you cannot script such.

Unfortunately, for me the virsh domifaddr my_vm does not work:

host$ virsh domifaddr my_vm
 Name       MAC address          Protocol     Address
-------------------------------------------------------------------------------

The table remains empty...

---

So, to help with a more permanent solution, I use a static IP address by doing so:

host$ virsh net-update default add ip-dhcp-host \
    "<host mac='52:54:00:11:22:33' name='buildserver' ip='192.168.122.123'/>" \
    --config

Then, if the VM is running, I complete stop it (i.e. sudo init 0 using the console in the virt-viewer). Finally, I restart the VM and assuming I did not type the wrong MAC or static IP address, I can now do:

host$ ssh 192.168.122.123

(Obviously, it takes a few seconds to boot, so give the VM time to do that before trying to ssh into it.)