How to add a disk to a new system without losing the data on it?

[Kliment Andreev]

> Hello,
> How do I add a disk containing data to a new system without erasing
> that data.

Check dmesg output to see the device name. Then try to mount that hard disk.
If everything went fine, you might want to mount that HDD on every boot so
check
/etc/fstab.