Just did a fresh install of Ubuntu Server 21.10 then Samba 4.13.14-Ubuntu via:

sudo apt install samba avahi-daemon

Whenever a macOS client connected to Samba reboots, I get the following email:

The Samba 'panic action' script, /usr/share/samba/panic-action,

was called for PID 24963 (/usr/sbin/smbd).



This means there was a problem with the program, such as a segfault.

Below is a backtrace for this process generated with gdb, which shows

the state of the program at the time the error occurred.  The Samba log

files may contain additional information about the problem.



If the problem persists, you are encouraged to first install the

samba-dbgsym package, which contains the debugging symbols for the Samba

binaries.  Then submit the provided information as a bug report to

Ubuntu by visiting this link:

https://launchpad.net/ubuntu/+source/samba/+filebug



[Thread debugging using libthread_db enabled]

Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

0x00007fb71b7be70f in __GI___wait4 (pid=25382, stat_loc=stat_loc@entry=0x7ffd2c2bb578, options=options@entry=0, usage=usage@entry=0x0) at ..

/sysdeps/unix/sysv/linux/wait4.c:30

#0  0x00007fb71b7be70f in __GI___wait4 (pid=25382, stat_loc=stat_loc@entry=0x7ffd2c2bb578, options=options@entry=0, usage=usage@entry=0x0) a

t ../sysdeps/unix/sysv/linux/wait4.c:30

#1  0x00007fb71b7be68b in __GI___waitpid (pid=<optimized out>, stat_loc=stat_loc@entry=0x7ffd2c2bb578, options=options@entry=0) at waitpid.c

:38

#2  0x00007fb71b72594b in do_system (line=<optimized out>) at ../sysdeps/posix/system.c:171

#3  0x00007fb71bc4842f in smb_panic_s3 () from /lib/x86_64-linux-gnu/libsmbconf.so.0

#4  0x00007fb71bcb8fdb in smb_panic () from /lib/x86_64-linux-gnu/libsamba-util.so.0

#5  0x00007fb71bcb92b5 in ?? () from /lib/x86_64-linux-gnu/libsamba-util.so.0

#6  <signal handler called>

#7  0x0000000000000000 in ?? ()

#8  0x00007fb71b26448f in dbwrap_record_delete () from /usr/lib/x86_64-linux-gnu/samba/libdbwrap.so.0

#9  0x00007fb71be805e5 in smbXsrv_session_logoff () from /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0

#10 0x00007fb71be62e17 in ?? () from /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0

#11 0x00007fb71b8ff8ea in tevent_common_invoke_immediate_handler () from /lib/x86_64-linux-gnu/libtevent.so.0

#12 0x00007fb71b8ff90e in tevent_common_loop_immediate () from /lib/x86_64-linux-gnu/libtevent.so.0

#13 0x00007fb71b905760 in ?? () from /lib/x86_64-linux-gnu/libtevent.so.0

#14 0x00007fb71b903afb in ?? () from /lib/x86_64-linux-gnu/libtevent.so.0

#15 0x00007fb71b8feb28 in _tevent_loop_once () from /lib/x86_64-linux-gnu/libtevent.so.0

#16 0x00007fb71b8fee0b in tevent_common_loop_wait () from /lib/x86_64-linux-gnu/libtevent.so.0

#17 0x00007fb71b903a8b in ?? () from /lib/x86_64-linux-gnu/libtevent.so.0

#18 0x00007fb71be4cc38 in smbd_process () from /usr/lib/x86_64-linux-gnu/samba/libsmbd-base.so.0

#19 0x000055cc54ea793d in smbd_accept_connection (ev=0x55cc551e1c20, fde=<optimized out>, flags=<optimized out>, private_data=<optimized out

>) at ../../source3/smbd/server.c:1014



#20 0x00007fb71b8ff4a1 in tevent_common_invoke_fd_handler () from /lib/x86_64-linux-gnu/libtevent.so.0

#21 0x00007fb71b90597f in ?? () from /lib/x86_64-linux-gnu/libtevent.so.0

#22 0x00007fb71b903afb in ?? () from /lib/x86_64-linux-gnu/libtevent.so.0

#23 0x00007fb71b8feb28 in _tevent_loop_once () from /lib/x86_64-linux-gnu/libtevent.so.0

#24 0x00007fb71b8fee0b in tevent_common_loop_wait () from /lib/x86_64-linux-gnu/libtevent.so.0

#25 0x00007fb71b903a8b in ?? () from /lib/x86_64-linux-gnu/libtevent.so.0

#26 0x000055cc54ea5c3b in smbd_parent_loop (parent=0x55cc551f5040, ev_ctx=0x55cc551e1c20) at ../../source3/smbd/server.c:1361

#27 main (argc=<optimized out>, argv=<optimized out>) at ../../source3/smbd/server.c:2214

A debugging session is active.

The /var/log/samba/log.smbd shows:

[2021/11/17 11:21:31.378403,  0] ../../lib/util/fault.c:159(smb_panic_log)

  ===============================================================

[2021/11/17 11:21:31.378525,  0] ../../lib/util/fault.c:160(smb_panic_log)

  INTERNAL ERROR: Signal 11: Segmentation fault in pid 24963 (4.13.14-Ubuntu)

[2021/11/17 11:21:31.378565,  0] ../../lib/util/fault.c:164(smb_panic_log)

  If you are running a recent Samba version, and if you think this problem is not yet fixed in the latest versions, please consider reporting this bug, see https://wiki.samba.org/index.php/Bug_Reporting

[2021/11/17 11:21:31.378595,  0] ../../lib/util/fault.c:169(smb_panic_log)

  ===============================================================

[2021/11/17 11:21:31.378621,  0] ../../lib/util/fault.c:170(smb_panic_log)

  PANIC (pid 24963): Signal 11: Segmentation fault in 4.13.14-Ubuntu

[2021/11/17 11:21:31.379046,  0] ../../lib/util/fault.c:274(log_stack_trace)

  BACKTRACE: 4 stack frames:

   #0 /lib/x86_64-linux-gnu/libsamba-util.so.0(log_stack_trace+0x34) [0x7fb71bcb63f4]

   #1 /lib/x86_64-linux-gnu/libsamba-util.so.0(smb_panic+0x2a) [0x7fb71bcb8fca]

   #2 /lib/x86_64-linux-gnu/libsamba-util.so.0(+0x232b5) [0x7fb71bcb92b5]

   #3 /lib/x86_64-linux-gnu/libc.so.6(+0x46520) [0x7fb71b717520]

[2021/11/17 11:21:31.379162,  0] ../../source3/lib/util.c:838(smb_panic_s3)

  smb_panic(): calling panic action [/usr/share/samba/panic-action 24963]

gdb: warning: Couldn't determine a path for the index cache directory.

30  ../sysdeps/unix/sysv/linux/wait4.c: No such file or directory.

[2021/11/17 11:21:32.341990,  0] ../../source3/lib/util.c:845(smb_panic_s3)

  smb_panic(): action returned status 0

[2021/11/17 11:21:32.342045,  0] ../../source3/lib/dumpcore.c:317(dump_core)

  coredump is handled by helper binary specified at /proc/sys/kernel/core_pattern

My clients are macOS Monterey with the following in their /etc/nsmb.conf:

signing_required = no

protocol_vers_map=6

port445=no_netbios

My Ubuntu Server 21.10's /etc/samba/smb.conf:

[global]

allow dns updates = disabled

bind interfaces only = Yes

client min protocol = SMB3_02

dcerpc endpoint servers = rpcecho

delete veto files = Yes

disable netbios = Yes

disable spoolss = Yes

dns forwarder = 192.168.1.1

dns proxy = No

enhanced browsing = No

# Next line requires catia (needed if no Windows clients?)

fruit:encoding = native

fruit:metadata = stream

# Next line never worked which is why I configure Avahi to set the icon

;fruit:model = Macmini7

# Do not use NFS access control entries

fruit:nfs_aces = No

# Enable extended attributes (requires streams_xattr)

fruit:resource = xattr

# Next line is already the default

;fruit:zero_file_id = Yes

host msdfs = No

inherit acls = Yes

inherit permissions = Yes

interfaces = lan

lm announce = No

load printers = No

log file = /var/log/samba/log.smbd

log level = 2

logging = file

max log size = 10000

# Next 2 lines defer mDNS config to Avahi

mdns name = mdns

multicast dns register = No

name resolve order = host bcast

pam password change = Yes

panic action = /usr/share/samba/panic-action %d

passwd chat = "*New Password:*" %n

 "*Reenter New Password:*" %n

 "*Password changed.*"

passwd program = /usr/bin/passwd %u

printcap cache time = 0

printcap name = /dev/null

printing = bsd

restrict anonymous = 2

rpc_daemon:spoolssd = disabled

rpc_server:epmapper = disabled

rpc_server:winreg = disabled

rpc_server:lsarpc = disabled

rpc_server:samr = disabled

rpc_server:netlogon = disabled

rpc_server:netdfs = disabled

rpc_server:dssetup = disabled

rpc_server:wkssvc = disabled

rpc_server:spoolss = disabled

rpc_server:svcctl = disabled

rpc_server:ntsvcs = disabled

rpc_server:eventlog = disabled

rpc_server:initshutdown = disabled

rpc_server:mdssvc = disabled

server max protocol = SMB3_11

server min protocol = SMB3_02

# Next line experimental until 4.15

server multi channel support = Yes

server role = standalone server

server services = rpc, smb

server string = %h server (Samba 4.13.14, Ubuntu 21.10)

show add printer wizard = No

smb ports = 445

unix password sync = Yes

use sendfile = Yes

veto files = /._*/.DS_Store/

vfs objects = catia fruit streams_xattr



[homes]

browseable = No

comment = Home Directory

fruit:time machine = No

guest ok = No

spotlight = No

valid users = %S

writable = Yes



[Backup]

comment = Time Machine

fruit:time machine = Yes

guest ok = No

path = /external/%U

spotlight = No

valid users = %U

writable = Yes

And for completeness, here's my /etc/avahi/services/samba.service:

<?xml version="1.0" standalone='no'?>

<!DOCTYPE service-group SYSTEM "avahi-service.dtd">

<service-group>

 <name replace-wildcards="yes">Saint James</name>

 <service>

   <type>_smb._tcp</type>

   <port>445</port>

 </service>

 <service>

   <type>_device-info._tcp</type>

   <port>0</port>

   <txt-record>model=Macmini7</txt-record>

 </service>

 <service>

   <type>_adisk._tcp</type>

   <txt-record>sys=waMa=0,adVF=0x100</txt-record>

   <txt-record>dk0=adVN=Backup,adVF=0x82</txt-record>

 </service>

</service-group>

Only need file sharing and Time Machine for the macOS Monterey clients (no Windows clients, no printing, no Active Directory, no DFS).

Anyone seeing this?