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I'd like to be able to switch between two Data volumes on the same macOS installed partition.

My thinking is that I could have one data volume for home and one for work. This would, essentially, allow me to "dual boot" with only one installation of the OS (since having the same OS installed twice is a waste of space and a hassle to maintain).

Is it possible to choose which data partition to mount on boot?

The current data volume disk1s5 would be my Data home volume, and an additional volume disk1s6 would be the Data work volume. 

~ % diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *251.0 GB   disk0
   1:                        EFI EFI                     314.6 MB   disk0s1
   2:                 Apple_APFS Container disk1         250.7 GB   disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +250.7 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume Macintosh HD            10.8 GB    disk1s1
   2:                APFS Volume Preboot                 80.9 MB    disk1s2
   3:                APFS Volume Recovery                528.5 MB   disk1s3
   4:                APFS Volume VM                      3.2 GB     disk1s4
   5:                APFS Volume Macintosh HD - Data     68.4 GB    disk1s5
...

The Data volume disk1s5 has its mount point /System/Volumes/Data. Could I remove the mount point from disk1s5 and set disk1s6's mount point instead?

~ % diskutil info disk1s5
   Device Identifier:         disk1s5
   Device Node:               /dev/disk1s5
   Whole:                     No
   Part of Whole:             disk1

   Volume Name:               Macintosh HD - Data
   Mounted:                   Yes
   Mount Point:               /System/Volumes/Data

   Partition Type:            41504653-0000-11AA-AA11-00306543ECAC
   File System Personality:   APFS
   Type (Bundle):             apfs
   Name (User Visible):       APFS
   Owners:                    Enabled

   OS Can Be Installed:       Yes
   Booter Disk:               disk1s2
   Recovery Disk:             disk1s3
   Media Type:                Generic
   Protocol:                  PCI-Express
...

And how would I set the new volume's Booter Disk to disk1s2?

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No, the firmlinks are bidirectional so you should have two pairs of filesystem if you need separate systems. The good news is that with space sharing and the smaller size of the system, having two Catalina around is ~22 GB for my Macs.

See the red boxes in the PDF for all the firm links you would have to remap and contend with...

enter image description here

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    In theory it may be possible to create such "bifurcal" Data volumes, however, the tools to remove/add APFS volumes from/to the APFS volume group (AFAIK required to use firmlinks) non-destructively don't exist. On the other hand: if the user installed apps in the Data volume exceed the ~11 GB limit, it's completely useless in terms of saving disk space. I would add: create a second or third user ([admin]/user-work/user-home) - this is the common way to separate work from private stuff.
    – klanomath
    Commented Jan 5, 2020 at 17:54
  • @klanomath Bingo, make a side volume, different encryption keys if you please, so that you can’t log in to the wrong account until it’s mounted or just leave the home folder elsewhere for all the tertiary accounts.
    – bmike ♦
    Commented Jan 5, 2020 at 18:50

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