Issue using samba 4.9 with Time Machine - samba

Question

TL;DR: Time Machine cannot create a new backup on my shared drive, but can add to an existing backup.
I'm running macOS Catalina and my Time Machine backs up to a Debian 10 server with NetAtalk and Avahi. Since Mavericks macOS has preferred SMB, and given SMB is marginally faster I decided to switch to using SMB for the Time Machine shares. On a fresh AFP share I can start a new Time Machine backup in System Preferences and it will create a new .sparseimage without complaint.
If I use the exact same directory (/usr/local/smb), so same permissions etc, and create a samba share, when Time Machine attempts to create a new backup it give the error: "Time Machine couldn’t complete the backup to SERVER.local. The backup disk image could not be created."
If I first connect to the share with AFP and do the initial backup, I can then connect with SMB and add subsequent incremental backups without error. I thought maybe a permissions issue, but for debugging purposes I have /usr/local/smb set to 0777 and still get the error.
ls -la showing permissions of the share point:
drwxrwxrwx 5 root smbusers 4096 Apr 3 12:35 smb
I find the following possibly helpful error in the log:
Failed to create '/Volumes/.timemachine/SERVER._smb._tcp.local/DDE06691-7411-41DD-8419-24FEFC21CE29/TimeMachine Set A - SMB/8E394711-7E3F-520B-800C-192D4F680177.sparsebundle', results: {
}, error: 13 Permission denied
afp.conf:
[Global]
; Global server settings
vol preset = default_for_all
log file = /var/log/netatalk.log
uam list = uams_dhx2.so,uams_clrtxt.so
save password = no
[default_for_all]
file perm = 0664
directory perm = 0774
cnid scheme = dbd
[Time Machine Set A - AFP]
path = /usr/local/smb
time machine = yes
vol size limit = 4000000
I'm using some smb.conf options suggested in this GitHub: https://gist.github.com/ChloeTigre/4c2022c0d1a281deedba6f7539a2e3ae
smb.conf:
[global]
## Browsing/Identification ###
# Change this to the workgroup/NT-domain name your Samba server will part of
workgroup = WORKGROUP
wins support = yes
#### Debugging/Accounting ####
# This tells Samba to use a separate log file for each machine
# that connects
log file = /var/log/samba/log.%m
# Cap the size of the individual log files (in KiB).
max log size = 1000
# We want Samba to only log to /var/log/samba/log.{smbd,nmbd}.
# Append syslog#1 if you want important messages to be sent to syslog too.
logging = file
# Do something sensible when Samba crashes: mail the admin a backtrace
panic action = /usr/share/samba/panic-action %d
###MacOS compatability stuff
guest account = smbguest
min protocol = SMB2
map acl inherit = yes
vfs objects = catia fruit streams_xattr
fruit:metadata = netatalk
fruit:model = MacSamba
fruit:posix_rename = yes
fruit:veto_appledouble = yes
durable handles = yes
kernel oplocks = no
kernel share modes =no
posix locking = no
smb2 leases = yes
#Turned off for testing compatability
#fruit:wipe_intentionally_left_blank_rfork = yes
#fruit:delete_empty_adfiles = yes
####### Authentication #######
# Server role. Defines in which mode Samba will operate. Possible
# values are "standalone server", "member server", "classic primary
# domain controller", "classic backup domain controller", "active
# directory domain controller".
#
# Most people will want "standalone server" or "member server".
# Running as "active directory domain controller" will require first
# running "samba-tool domain provision" to wipe databases and create a
# new domain.
server role = standalone server
obey pam restrictions = yes
# This boolean parameter controls whether Samba attempts to sync the Unix
# password with the SMB password when the encrypted SMB password in the
# passdb is changed.
unix password sync = yes
# For Unix password sync to work on a Debian GNU/Linux system, the following
# parameters must be set (thanks to Ian Kahan <<kahan#informatik.tu-muenchen.de> for
# sending the correct chat script for the passwd program in Debian Sarge).
passwd program = /usr/bin/passwd %u
passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
# This boolean controls whether PAM will be used for password changes
# when requested by an SMB client instead of the program listed in
# 'passwd program'. The default is 'no'.
pam password change = yes
# This option controls how unsuccessful authentication attempts are mapped
# to anonymous connections
map to guest = bad user
######Security#######
security = user
valid users = #smbusers
username map = /etc/samba/users.map
guest ok = no
# Allow users who've been granted usershare privileges to create
# public shares, not just authenticated ones
usershare allow guests = yes
#======================= Share Definitions =======================
[TimeMachine Set A - SMB]
path = /usr/local/smb
comment = SMB Time Machine Destination Set A
browsable = yes
writeable = yes
create mode = 0664 #tried turning this off, no fix
directory mode = 0777 #tried turning this off, no fix
vfs objects = catia fruit streams_xattr
fruit:aapl = yes
fruit:time machine = yes
#guest ok = yes
fruit:time machine max size = 3.9T #tried turning this off, no fix
inherit acls = yes

Answer 1

As I was so helpfully informed here the issue boiled down to one variable. I needed to change fruit:metadata = netatalk to fruit:metadata = stream.

Answer 2

Thought I'd post some additional info for people. My currently working smb.conf is as follows. Note this is on Debian 10 (Buster) so things like password change command will be different on other distributions. Also note that the order of modules in the setting vfs objects = catia fruit streams_xattr is significant and important.
# NOTE: Whenever you modify this file you should run the command
# "testparm" to check that you have not made any basic syntactic
# errors.
[global]
workgroup = WORKGROUP
min protocol = SMB2
log file = /var/log/samba/log.%m
max log size = 5000
logging = file
security = USER
panic action = /usr/share/samba/panic-action %d
server role = standalone server
obey pam restrictions = yes
unix password sync = yes
passwd program = /usr/bin/passwd %u
passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
pam password change = yes
username map = /etc/samba/users.map
map to guest = bad user
guest account = XXXYOURGUESTACCOUNT
# Time Machine settings
vfs objects = catia fruit streams_xattr
fruit:model = MacSamba
fruit:advertise_fullsync = true
fruit:metadata = stream
fruit:veto_appledouble = no
#default is yes, not necessary to specify fruit:posix_rename = no
#default is yes, not necessary to specify fruit:zero_file_id = yes
fruit:wipe_intentionally_left_blank_rfork = yes
fruit:delete_empty_adfiles = yes
ea support = yes
#default is yes, not necessary to specify fruit:aapl = yes
# Make share visible to Windows
#Disabled for a Mac-Only network
# lanman auth = no
# ntlm auth = yes
# wins support = yes
# local master = yes
# preferred master = yes
# Allow symlinks
# follow symlinks = yes
# wide links = yes
# unix extensions = no
#======================= Share Definitions =======================
[SHARED DRIVE]
path = /PATH/TO/YOUR/SHARED/FOLDER
valid users = #YOURGUESTUSERGROUP
writable = yes
durable handles = yes
kernel oplocks = no
kernel share modes = no
posix locking = no
vfs objects = catia fruit streams_xattr
#default is yes, not necessary to specify ea support = yes
#default is yes, not necessary to specify browseable = yes
read only = no
inherit acls = yes
fruit:time machine = yes
fruit:metadata = stream
fruit:locking = netatalk
guest ok = yes
[Time Machine]
path = /PATH/TO/YOUR/SHARED/FOLDER
valid users = #YOURGUESTUSERGROUP
writable = yes
durable handles = yes
kernel oplocks = no
kernel share modes = no
posix locking = no
vfs objects = catia fruit streams_xattr
#default is yes, not necessary to specify ea support = yes
browseable = no
read only = no
inherit acls = yes
fruit:time machine = yes
fruit:metadata = stream
fruit:locking = netatalk
fruit:time machine max size = 1.9T
Also note that The Samba build with Debian 10 currently does not have built-in support for advertising Time Machine shares. Normally specifying fruit:time machine = yes will trigger Samba to advertise a Time Machine destination via Avahi, but this specific support is not built with the Samba included in Debian 10. You'll need to configure a .service definition in /etc/avahi/services/. I created time_machine_advert.service in that folder. You'll need to restart avahi to be sure it gets applied with sudo systemctl restart avahi. I have two Time Machine destinations. Multiples can be advertised within a single file by simply duplicating the txt record and incrementing dkX, i.e. dk1, dk2 etc.
<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
<name replace-wildcards="yes">%h</name>
<service>
<type>_adisk._tcp</type>
<txt-record>sys=waMa=0,adVF=0x100</txt-record>
<txt-record>dk0=adVN=SAMBA SHARE NAME EXACTLY,adVF=0x82</txt-record>
<txt-record>dk1=adVN=SAMBA SHARE NAME #2 EXACTLY,adVF=0x82</txt-record>
</service>
<service>
<type>_smb._tcp</type>
<port>445</port>
</service>
</service-group>
There are some additional useful sites for Samba configuration with regards to Time Machine here:
Samba team's official guide to Time Machine configuration, although this alone didn't get a working config for me: https://wiki.samba.org/index.php/Configure_Samba_to_Work_Better_with_Mac_OS_X
smb.conf reference: https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html
vfs_fruit (the Apple compatibility module for Samba) reference https://www.samba.org/samba/docs/current/man-html/vfs_fruit.8.html
Ken Murphy's smb.conf on GitHub that finally pushed me over the edge and got my setup working: https://github.com/KenMurphy/SambaConfigs/blob/master/smb.conf
A general Samba on Debian guide: https://www.antoneliasson.se/journal/time-machine-compatible-samba-on-debian-buster/