MacOS file system check

To see if you new APFS file system is consistent,  you can:

$ sudo fsck_apfs -ln /dev/disk1s1

Let me explain this in details:

• sudo - assume admin rights
• fsck_apfs - the low level program to check an APFS file system
• -ln - scan this in "live mode" and do "no changes"
• /dev/disk1s1 - the name of your main disk. You can find this by either doing a "df ~" or "diskutil list". The later gives the following output on my system:

$ diskutil list

/dev/disk0 (internal):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                         500.3 GB   disk0

   1:                        EFI EFI                     314.6 MB   disk0s1

   2:                 Apple_APFS Container disk1         500.0 GB   disk0s2

/dev/disk1 (synthesized):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      APFS Container Scheme -                      +500.0 GB   disk1

                                 Physical Store disk0s2

   1:                APFS Volume Macintosh HD            478.9 GB   disk1s1

   2:                APFS Volume Preboot                 47.5 MB    disk1s2

   3:                APFS Volume Recovery                512.8 MB   disk1s3

   4:                APFS Volume VM                      1.1 GB     disk1s4

 If this tells you that you should repair your disk, you must boot your Mac into single user mode (console mode). To do this, reboot and press CMD+S during reboot. You will get a unix console with a root prompt.

here you can run

# fsck_apfs -y /dev/disk1s1

-y means here: repair without asking