[Samba] Troubleshooting high CPU load

Denis Cardon dcardon at tranquil.it
Thu Jan 25 19:20:20 UTC 2018

Hi Mark,

> I'm investigating high CPU load on a domain member server (file server)
> after an upgrade from 4.5.5 to 4.6.2. The problem continued after a
> subsequent upgrade to 4.6.7.
> I turned up the log level to 3 for a short time and looked at the logs. One
> thing I notice is some entries like this:
> [2018/01/24 18:28:37.933498,  3]
> ../source3/auth/user_krb5.c:164(get_user_from_kerberos_info)
>   get_user_from_kerberos_info: Username STA\I7X4-42G-12$ is invalid on this
> system
> [2018/01/24 18:28:37.933525,  3]
> ../source3/auth/auth_generic.c:145(auth3_generate_session_info_pac)
>   auth3_generate_session_info_pac: Failed to map kerberos principal to
> [2018/01/24 18:28:37.933582,  3]
> ../source3/smbd/smb2_server.c:3097(smbd_smb2_request_error_ex)
>   smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1]
> status[NT_STATUS_ACCESS_DENIED] || at ../source3/smbd/smb2_sesssetup.c:134
> [2018/01/24 18:28:37.934058,  2]
> ../source3/smbd/close.c:788(close_normal_file)
>   STA\jimenez closed file 2017dwgs/17020/Revit/633 Folsom
> Street_TSE_Struct_backup/_contents.2154.dat (numopen=504) NT_STATUS_OK
> [2018/01/24 18:28:37.934320,  3]
> ../source3/smbd/server_exit.c:246(exit_server_common)
> [2018/01/24 18:28:37.934340,  3] ../source3/smbd/dir.c:656(dptr_create)
> The name  STA\I7X4-42G-12$ is a machine name. Is this one of those normal
> and expected error messages or does it indicate a problem?

Computer accounts are mostly like user accounts, and it can be used to 
connect to network shares. For example workstation computer account is 
used to connect to SYSVOL share to download GPO at machine startup.

It is uncommon to have a workstation connect to a fileserver, although 
there are some use cases. If my memory is right, the server is 
configured with rfc2307, so it get uidnumber and gidnumber from LDAP 
tree, and there is probably no uidnumber on workstation accounts.

One option is to add uidnumber/gidnumber to workstations to avoid this 
error message, or to switch to rid mapping (but you'll need to remap ACL 
on network shares). But anyway, like I said before, there is probably no 
use for you workstation to connect to the server, so you may have to 
check why it is doing that.

For the high load, I don't know if it is linked to that. If the query 
non resolving query is coming in all the time, it may be usefull to add 
some negative cache time on winbind.



> When I run "wbinfo -i" it returns valid info for domain users. Is it
> supposed to do the same for machine accounts?
> If this is a red herring, do you have any suggestions on how to proceed?
> Thanks.

Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint SĂ©bastien sur Loire
tel : +33 (0)

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