- Solved
I'm submitting this in the hope that it gets fixed even though I suspect that it may be the result of the macOS 12.3.1 update. It actually started happening well before rc8 was released. Last successful backup was on April 30th. Now I can create a new share for time machine backups and the first backup will be successful. Subsequent backups will fail with an error in time machine "Failed to attach using DiskImages2".
Time Machine log-
2022-05-11 22:03:04 Cleared pending cancellation request
2022-05-11 22:03:10 Not prioritizing backups with priority errors. lockState=0
2022-05-11 22:03:10 Starting manual backup
2022-05-11 22:03:10 Rejecting candidate mount point: /Volumes/TM_mini, not owned by root
2022-05-11 22:03:10 Attempting to mount 'smb://[email protected]/TM_mini'
2022-05-11 22:03:10 Mounted 'smb://[email protected]/TM_mini' at '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini' (420.71 GB of 1.05 TB available)
2022-05-11 22:03:10 Initial network volume parameters for 'TM_mini' {disablePrimaryReconnect: 0, disableSecondaryReconnect: 0, reconnectTimeOut: 60, QoS: 0x0, attributes: 0x1C}
2022-05-11 22:03:10 Configured network volume parameters for 'TM_mini' {disablePrimaryReconnect: 0, disableSecondaryReconnect: 0, reconnectTimeOut: 30, QoS: 0x20, attributes: 0x1C}
2022-05-11 22:03:11 Skipping periodic backup verification: not needed for an APFS sparsebundle
2022-05-11 22:03:11 'm1-mini.sparsebundle' does not need resizing - current logical size is 996.15 GB (996,147,200,000 bytes), size limit is 996.15 GB (996,147,200,000 bytes)
2022-05-11 22:03:11 Mountpoint '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini' is still valid
2022-05-11 22:03:11 Checking for runtime corruption on '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini/m1-mini.sparsebundle'
2022-05-11 22:03:47 Failed to attach using DiskImages2 to url '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini/m1-mini.sparsebundle', error: Error Domain=NSPOSIXErrorDomain Code=19 "Operation not supported by device" UserInfo={DIErrorVerboseInfo=Failed to initialize IO manager: Failed opening folder for entries reading}
2022-05-11 22:03:47 Failed to unmount '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini', Disk Management error: {
2022-05-11 22:03:47 Failed to unmount '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini', error: Error Domain=com.apple.diskmanagement Code=0 "No error" UserInfo={NSDebugDescription=No error, NSLocalizedDescription=No Error.}
2022-05-11 22:03:47 Waiting 60 seconds and trying again.
2022-05-11 22:03:47 Cancelling backup because volume '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini' was unmounted.
2022-05-11 22:03:47 Requested backup cancellation or termination
2022-05-11 22:03:48 Backup cancelled (22: BACKUP_CANCELED)
2022-05-11 22:03:48 Failed to unmount '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini', Disk Management error: {
2022-05-11 22:03:48 Failed to unmount '/Volumes/.timemachine/10.0.1.20/DEFC5403-1530-4ACF-8A8C-004E23519E00/TM_mini', error: Error Domain=com.apple.diskmanagement Code=0 "No error" UserInfo={NSDebugDescription=No error, NSLocalizedDescription=No Error.}
Current SMB extra config-
#unassigned_devices_start
#Unassigned devices share includes
include = /tmp/unassigned.devices/smb-settings.conf
#unassigned_devices_end
#macOS config start
server multi channel support = no
#macOS config end
#vfs_recycle_start
#Recycle bin configuration
[global]
syslog only = Yes
syslog = 0
logging = 0
log level = 0 vfs:0
#vfs_recycle_end
#macOS config start
vfs objects = catia fruit streams_xattr
fruit:nfs_aces = no
fruit:zero_file_id = yes
fruit:metadata = stream
fruit:encoding = native
spotlight backend = tracker
[Media]
path = /mnt/user/Media
veto files = /._*/.DS_Store/
delete veto files = yes
spotlight = yes
[mini_SMB]
path = /mnt/user/mini_SMB
veto files = /._*/.DS_Store/
delete veto files = yes
spotlight = yes
[ccc_mini_backup]
path = /mnt/user/ccc_mini_backup
veto files = /._*/.DS_Store/
delete veto files = yes
spotlight = yes
[ccc_raid1_backup]
path = /mnt/user/ccc_raid1_backup
veto files = /._*/.DS_Store/
delete veto files = yes
spotlight = yes
#macOS config end