Unable to change file permissions on Ubuntu Bash for Windows 10

I was trying to use an ssh instance and I recieved this error:

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@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
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Permissions 0777 for 'privkey.pem' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
Load key "privkey.pem": bad permissions
Permission denied (publickey).

Which is odd. I tried to change the permission using the 'chmod' command, but that didn't seem to work. The bash gave the impression that the command registered, but I checked the permissions of the key and it was still at 777. I opened my git bash and I was able to ssh into my instance with no problem, and the permissions were not 777 as well.

Answer

If you're referencing files in the Windows file system, they do not, by default, retain Linux permissions. However, there's a way to enable that. Edit or create (using sudo) /etc/wsl.conf and add the following:

[automount]
options = "metadata"

Shut down all WSL instances and restart an instance, and any chmod changes are now retained.