I had a hell of a time trying to figure out why after upgrading the CentOS Samba package the samba shares quit working. Every time someone tried to access the share, the smb service would crash. I had this system configured to use active directory credentials and it worked well for a time, but no longer.

After much digging I found my problem to be the lack of a krb5.keytab file. This is due to my using PowerBroker Open instead of kerberos for authentication.

The solution was to add this line to my samba config:

kerberos method = system keytab

That one bit made all the difference. My current samba config is as follows with no more crashing: (Updated 8/29 to add workgroup name)

[global]
     security = ADS
     passdb backend = tdbsam
     realm = DOMAIN
     workgroup = NETBIOS_DOMAIN_NAME
     encrypt passwords = yes
     lanman auth = no
     ntlm auth = no
     kerberos method = system keytab
     obey pam restrictions = yes
     winbind enum users = yes
     winbind enum groups = yes

Update 8/29/2018: After updating and rebooting my smb service refused to start. It kept giving this very unhelpful message:

 ../source3/auth/auth_util.c:1399(make_new_session_info_guest)
create_local_token failed: NT_STATUS_NO_MEMORY
../source3/smbd/server.c:2011(main)
ERROR: failed to setup guest info.
smb.service: main process exited, code=exited, status=255/n/a
Failed to start Samba SMB Daemon.

I couldn’t find any documentation on this and eventually resorted to just messing around with my smb.conf file. What fixed it was adding this to my configuration:

workgroup = NETBIOS_DOMAIN_NAME

Replacing NETBIOS_DOMAIN_NAME with the old NetBIOS style domain name (what you would put in the domain part of domain\username for logging in) for my company. It worked!