I recently faced the problem of not being able to update Ubuntu 12.04 to 14.04 in my DigitalOcean droplet.
Despite these great instructions: https://www.digitalocean.com/community/tutorials/how-to-upgrade-ubuntu-12-04-lts-to-ubuntu-14-04-lts
It did not work because there were missing files.
I had to manually edit the sources list
sudo nano /etc/apt/sources.list
And uncomment the original DEB package sources, and comment the Digital Ocean mirror packages.
Hope it helps!
I am using a very simple digitalocean basic server with 512mb RAM, and using Ubuntu 12.04 64bits
I tried the recommendations here:
But still keeps crashing, so I have looked for further information, and this one seems to be a good guide to tweak the server, both apache and mysql:
I think that the key point for me is that I chose Ubuntu 64 bits without being aware that 64 bits Ubuntu takes around 50% more memory than 32 bits
So now I guess the solution is to downgrade to a 32bit server, which will be a bit of a pain… but if this solves the performance issue, then I will surely do it.