Site migrations go wrong in a predictable way: someone points the domain at the new server before the new server is ready, and the site is broken in public while they fix it. The whole job is a sequencing problem, and the sequence is not complicated.
Build it on the new host before you point anything at it
Copy the files, import the database, and get the site running on the new server under a temporary hostname while the old one is still serving your visitors. Nothing you do at this stage is visible to anyone. Work through the site properly: log in to the admin, load a page that hits the database, submit a form, complete a test checkout if you sell anything.
- Match the PHP version to what the site currently runs on, then upgrade afterwards — one change at a time
- Check file permissions and ownership, the usual cause of a white screen after a copy
- Update database credentials in the site config; they will not match the old ones
- Take a fresh copy of the database as close to cutover as you can, so you do not lose orders or comments written in between
Lower your DNS TTL a day ahead
TTL is how long resolvers around the world are allowed to cache your DNS record. If it is set to 86400 seconds, some visitors will keep going to the old server for up to 24 hours after you change it. Drop it to 300 seconds at least one full TTL before the migration, and the switch propagates in minutes rather than a day.
Cut over, then verify from outside
- Put the old site into a read-only state if it accepts orders or comments, so nothing is written to a database you are about to replace
- Sync the database one final time
- Change the A record — or the nameservers, if you are moving DNS as well
- Issue the SSL certificate on the new host once the record resolves there
- Test the live domain from a device that has never visited the new server: a phone on mobile data works
- Raise the TTL back to something sensible once you are happy
The week after
Watch the server error log rather than the homepage. Most migration problems surface on a page nobody thought to test — a contact form that cannot send mail because SPF was never updated, a cron job that was set up on the old host and quietly stopped, an image path that was absolute. Check that mail is being delivered and that scheduled tasks are running.
If this sounds like a job you would rather hand over: migration is free on every Serverlys hosting plan, and we do it in this order — staging first, your approval, then DNS.
Questions about anything above? We answer them without a sales script.