I have a perfect system ISPConfig (jessie) powered, and I have to say it is working great! ...but it suddenly warned me that I had to do some system updates. So far so good, but I'm a little worried about the options... Do it from the ISPConfig interface: it says that it will use aptitude... all my installs updates until now were done with apt-..., and it is not good practice to mix the two. Also, it mentions the "-y" option, what about ISPConfig special configs, does it looks about them after the update? Do it from console: This way, I'll see which software wants to override previous conf files, ok, so I can make note of that but what do I have to launch after some update has reverted its config file? Production concern: as my server is mainly a mail server, I'm quite anxious that if mess happens during OS upgrade, I'll have to roll back to the previous backup (a few minutes ago), but even a few minutes ago might have leaked some mail any user mailbox, and if I rollback, this mail will be lost. I know of the "maintenance mode" in interface/main config/misc, but it doesn't prevent mail from coming while I'm doing the upgrade, and if any mail gets through, and I have to rollback for any reason, this mail will be lost forever... Explain that to the customer. What is the recommended way of updating the system (needed, at least monthly, but weekly sometimes, as there might be security fixes) securely, I mean, the upgrade might fail, but we can safely go back from a backup?