I'm able to erase a partition using the Disk Utility, but I want to change the name without losing data. How is it possible?
To rename the volume, enter the following in Terminal:
/usr/sbin/diskutil rename oldname newname
/usr/sbin/diskutil rename "Macintosh HD" "Mac Disk"
You can also right-click a partition in Finder (in Computername at the top level of the hierarchy), select Get Info, and enter the new name there.
Or just go to Finder and change the name in the left hand column, just like a file.
I had an issue where finder was repeatedly restarting which made the mac unusable. Went into single-user mode and spotted that the volume had a lengthy name of strange characters. Could not rename it - since GUI was unavailable and the rename command in single-user needs you to type the name (without being able to cut/paste). This in in High Sierra on a 2015 mac mini. Turns out if you boot into recovery mode with CMD-R, go into disk utility, highlight the disk with the bad volume name then click the name beside the picture of the disk (or do File Rename) it lets you change it. This fixed all my problems and the machine seems fine now.