Configure Samba and Avahi on a Linux server to use as a Time Machine for macOS clients.

smb.conf

[global]
## General
server role = standalone server
workgroup = WORKGROUP
server smb encrypt = desired

## Logging
logging = file
log file = /var/log/samba/log.%m
log level = 2
max log size = 1000

## Auth
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
map to guest = bad user

## Performance
# From https://calomel.org/samba_optimize.html
use sendfile = yes

## Apple TimeMachine support
# See https://blog.jhnr.ch/2023/01/09/setup-apple-time-machine-network-drive-with-samba-on-ubuntu-22.04/
# Load in modules (order is critical!)
# See https://blog.al4.co.nz/2024/04/samba-config-for-apple-time-machine/
vfs objects = acl_xattr fruit streams_xattr aio_pthread
# See https://stackoverflow.com/questions/58496277/samba-4-10-server-config-using-module-vfs-fruit-changes-file-creation-mask-fo
fruit:nfs_aces = no

# The name of the share needs to match what's in time-machine.service for Avahi and cannot have spaces
[Time-Machine-Alice]
path = /backup/alice
fruit:time machine = yes
fruit:time machine max size = 1T
valid users = alice
writable = yes

[Time-Machine-Bob]
path = /backup/bob
fruit:time machine = yes
fruit:time machine max size = 1T
valid users = bob
writable = yes

[homes]
comment = Home Directories
browseable = no
writable = yes
valid users = %S

time-machine.service

<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
  <name replace-wildcards="yes">%h</name>
  <service>
    <type>_smb._tcp</type>
    <port>445</port>
  </service>
  <service>
    <type>_device-info._tcp</type>
    <port>0</port>
    <txt-record>model=RackMac</txt-record>
  </service>
  <service>
    <type>_adisk._tcp</type>
    <txt-record>dk0=adVN=Time-Machine-Alice,adVF=0x82</txt-record>
    <txt-record>sys=waMa=0,adVF=0x100</txt-record>
  </service>
  <service>
    <type>_adisk._tcp</type>
    <txt-record>dk0=adVN=Time-Machine-Bob,adVF=0x82</txt-record>
    <txt-record>sys=waMa=0,adVF=0x100</txt-record>
  </service>
</service-group>