Month: August 2025

Sometimes you just need good old serial console access — maybe to troubleshoot a headless server, recover from a broken network config, or simply because SSH isn’t an option. If your Linux host is running on VMware ESXi 5.5.0, you can actually hook into its serial console by using a named pipe and a bit of socat magic.

Here’s how to get it done.

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1. Enable serial access inside the Linux VM

First, make sure the VM itself is ready to serve a serial console session. On most modern Linux distros using systemd, this means enabling the serial-getty service:

# systemctl enable serial-getty@ttyS0.service

This will make the login prompt available on ttyS0 after each reboot.

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2. List your VMs in ESXi

SSH into your ESXi host and get the list of registered VMs:

# vim-cmd vmsvc/getallvms

Find the VM you want and note its ID (the number in the first column).

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3. Power off the VM

You can either shut it down from inside the guest OS:

# poweroff

Or, if that’s not possible, do it from ESXi:

# vim-cmd vmsvc/power.off ID

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4. Make sure it’s really powered off

Double-check the VM’s state:

# vim-cmd vmsvc/power.getstate ID

It should return Powered off.

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5. Edit the VM’s configuration

Open the VM’s .vmx file (located in its directory on the datastore) and add these lines:

serial0.fileType = "pipe"
serial0.fileName = "/vmfs/volumes/datastore1/vm-host-dir/serial0.pipe"
serial0.tryNoRxLoss = "TRUE"
serial0.yieldOnMsrRead = "TRUE"
serial0.present = "TRUE"
serial0.pipe.endPoint = "server"

Make sure to adjust the path to match your VM’s folder.

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6. Power the VM back on

# vim-cmd vmsvc/power.on ID

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7. Get socat on ESXi

ESXi doesn’t come with socat built-in, but we need it to connect to our serial pipe.

You can build it yourself using my repo here:
https://github.com/heroseloi/socat-builder

Once compiled, SCP it over to your ESXi host.

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8. Connect to the serial console

With socat in place, run:

# socat -,raw,echo=0 UNIX-CONNECT:/vmfs/volumes/datastore1/vm-host-dir/serial0.pipe

If all went well, you should see something like:

Rocky Linux 8.10 (Green Obsidian)
Kernel 6.15.9-1.el8.elrepo.x86_64 on an x86_64

server login:

Boom — you’re in the VM’s console without needing a virtual display.

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Summary

That’s it — you’ve just set up a working serial console for a Linux VM on ESXi 5.5.0.
The key steps were:

1. Enabling the serial-getty service in Linux.
2. Configuring the VMX file to use a named pipe for serial output.
3. Using socat to hook into that pipe from ESXi.

It’s a handy trick for rescue situations, minimal VM setups, or when you just want a bit of retro charm in your sysadmin life.

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