[Samba] File timestamp issue

[Anders Östling]

I am not convinced that it's a Samba issue, but someone might be able to
answer anyway

We replicate directories and files from a Windows 2019 server to two
destinations, both are supposed to be used in case of a disaster, but are
also used for some specific tasks. One of the replication targets is a
physical Windows 2012 server and the other one an Ubuntu/Samba virtual
machine. The Samba VM is configured as a member server. It has been used by
a group of people for accessing (mostly) static files for years without any
problems.
Replication is done using Robocopy in mirroring mode which is supposed to
only replicate changed or new files to the two target systems. Herein lies
the problem. The selective mirroring works fine between Windows and
Windows. When replicating towards the Samba machine, timestamps seem to be
ignored since each run is a full replication. I *think* that this behaviour
started after upgrading the Samba from 4.12 to 4.15 recently.
When I look at the timestamps on Windows and Linux/Ext4, they look
identical, down to the second.

The command used is ROBOCOPY SOURCE TARGET /MIR /NDL /NFL /NP /COPYALL

So, is there a Robocopy guru out there that can advise us?

PS1. The smb.conf looks like this

[global]
netbios name = HP-SRV03
bind interfaces only = yes
interfaces = lo ens3
realm = XAGAREN.SE
server role = MEMBER SERVER
security = ADS
workgroup = HPLTS
idmap_ldb:use rfc2307 = yes
idmap config * : backend = tdb
idmap config * : range = 10000-20000
idmap config HPLTS : backend = rid
idmap config HPLTS : range = 30000-40000
dedicated keytab file = /etc/krb5.keytab
kerberos method = secrets and keytab
winbind refresh tickets = yes
winbind offline logon = yes
winbind enum users = yes
winbind enum groups = yes
winbind nested groups = yes
winbind expand groups = yes
winbind use default domain = yes
os level = 20
domain master = no
local master = no
preferred master = no
map to guest = bad user
host msdfs = no
client min protocol = SMB2
server min protocol = SMB2
client max protocol = SMB3
unix extensions = no
reset on zero vc = yes
hide unreadable = yes
acl group control = yes
acl map full control = yes
map acl inherit = yes
ea support = yes
vfs objects = acl_xattr
store dos attributes = yes
dos filemode = yes
dos filetimes = yes
restrict anonymous = 2
strict allocate = yes
guest account = bock
guest ok = yes
load printers = no
printing = bsd
printcap name = /dev/null
disable spoolss = yes
log level = 1

[<share names>]
comment = "comment"
path = /share2/<share name>
read only = no
guest ok = no

PS2. An additional side effect of the recent Samba upgrade is that we had
to disable the user.map functionality (root/Administrator mapping) since
Samba does not like this anymore. The replication script on the Windows
side runs as Administrator, and I have seen other postings that this is now
disapproved by Samba. So removing the user.map functionality solved that.

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"A *wise* man once told me - Any idiot can do backups, but it takes a
genius to successfully restore"

Anders Östling
+46 768 716 165 (Mobil)