This assumes you are using VirtualBox as your provider, which you are if you’re using a pre-built vagrant configuration like I am with VVV.

I was running out of RAM and crashing my VM while trying to import a 9MB WXR file into a WordPress install.

First, I tried adding a swapfile so I could get some virtual memory. I was able to do that with these instructions from Digital Ocean, but I wasn’t sure how to make it persistent after a vagrant destroy and didn’t want to have to set this up every time I booted up the VM.

Finally, I found this thread in the issues for VVV with the answer.

Create a Customfile in the same directory as your Vagrantfile, and add the contents below, changing 2048 to be whatever value you want to increase your VM’s RAM to.

config.vm.provider :virtualbox do |v|
  v.customize ["modifyvm", :id, "--memory", 2048]
end

Save the file, and then do a vagrant reload and you should be able to verify with top or free -m that you now have some additional memory in the VM.

I went with 2GB. There has been some discussion of increasing the default in VVV from 512MB, however I think that would be an issue for people on laptops, especially running MacBook Air’s with only 4GB of RAM.