smbd - server to provide SMB/CIFS services to clients
smbd [ -D ] [ -a ] [ -i ] [ -o ] [ -P ] [ -h ] [ -V ] [ -d <debug level> ] [ -l
<log directory> ] [ -p <port number> ] [ -O <socket option> ] [ -s <configuration file>
This program is part of the Samba suite.
smbd is the server daemon that provides filesharing and printing services to Windows
clients. The server provides filespace and printer services to clients using the SMB (or
CIFS) protocol. This is compatible with the LanManager protocol, and can service LanMan-
ager clients. These include MSCLIENT 3.0 for DOS, Windows for Workgroups, Windows
95/98/ME, Windows NT, Windows 2000, OS/2, DAVE for Macintosh, and smbfs for Linux.
An extensive description of the services that the server can provide is given in the man
page for the configuration file controlling the attributes of those services (see
This man page will not describe the services, but will concentrate on the administrative
aspects of running the server.
Please note that there are significant security implications to running this server, and
the smb.conf(5) manpage should be regarded as mandatory reading before proceeding with
A session is created whenever a client requests one. Each client gets a copy of the
server for each session. This copy then services all connections made by the client during
that session. When all connections from its client are closed, the copy of the server for
that client terminates.
The configuration file, and any files that it includes, are automatically reloaded every
minute, if they change. You can force a reload by sending a SIGHUP to the server. Reload-
ing the configuration file will not affect connections to any service that is already
established. Either the user will have to disconnect from the service, or smbd killed and
-D If specified, this parameter causes the server to operate as a daemon. That is, it
detaches itself and runs in the background, fielding requests on the appropriate
port. Operating the server as a daemon is the recommended way of running smbd for
servers that provide more than casual use file and print services. This switch is
assumed if smbd is executed on the command line of a shell.
-a If this parameter is specified, each new connection will append log messages to the
log file. This is the default.
-i If this parameter is specified it causes the server to run "interactively", not as
a daemon, even if the server is executed on the command line of a shell. Setting
this parameter negates the implicit deamon mode when run from the command line.
-o If this parameter is specified, the log files will be overwritten when opened. By
default, smbd will append entries to the log files.
-P Passive option. Causes smbd not to send any network traffic out. Used for debugging
by the developers only.
-h Prints the help information (usage) for smbd.
-v Prints the version number for smbd.
-d <debug level>
debuglevel is an integer from 0 to 10. The default value if this parameter is not
specified is zero.
The higher this value, the more detail will be logged to the log files about the
activities of the server. At level 0, only critical errors and serious warnings
will be logged. Level 1 is a reasonable level for day to day running - it generates
a small amount of information about operations carried out.
Levels above 1 will generate considerable amounts of log data, and should only be
used when investigating a problem. Levels above 3 are designed for use only by
developers and generate HUGE amounts of log data, most of which is extremely cryp-
Note that specifying this parameter here will override the log level file.
-l <log directory>
If specified, log directory specifies a log directory into which the "log.smbd" log
file will be created for informational and debug messages from the running server.
The log file generated is never removed by the server although its size may be con-
trolled by the max log size option in the smb.conf(5) file. Beware: If the direc-
tory specified does not exist, smbd will log to the default debug log location
defined at compile time.
The default log directory is specified at compile time.
-O <socket options>
See the socket options parameter in the smb.conf(5)
file for details.
-p <port number>
port number is a positive integer value. The default value if this parameter is not
specified is 139.
This number is the port number that will be used when making connections to the
server from client software. The standard (well-known) port number for the SMB over
TCP is 139, hence the default. If you wish to run the server as an ordinary user
rather than as root, most systems will require you to use a port number greater
than 1024 - ask your system administrator for help if you are in this situation.
In order for the server to be useful by most clients, should you configure it on a
port other than 139, you will require port redirection services on port 139,
details of which are outlined in rfc1002.txt section 4.3.5.
This parameter is not normally specified except in the above situation.
-s <configuration file>
The file specified contains the configuration details required by the server. The
information in this file includes server-specific information such as what printcap
file to use, as well as descriptions of all the services that the server is to pro-
vide. See smb.conf(5) for more information. The default configuration file name
is determined at compile time.
If the server is to be run by the inetd meta-daemon, this file must contain suit-
able startup information for the meta-daemon. See the UNIX_INSTALL.html document
or whatever initialization script your system uses).
If running the server as a daemon at startup, this file will need to contain an
appropriate startup sequence for the server. See the UNIX_INSTALL.html document for
If running the server via the meta-daemon inetd, this file must contain a mapping
of service name (e.g., netbios-ssn) to service port (e.g., 139) and protocol type
(e.g., tcp). See the UNIX_INSTALL.html document for details.
This is the default location of the smb.conf server configuration file. Other com-
mon places that systems install this file are /usr/samba/lib/smb.conf and
This file describes all the services the server is to make available to clients.
See smb.conf(5) for more information.
On some systems smbd cannot change uid back to root after a setuid() call. Such systems
are called trapdoor uid systems. If you have such a system, you will be unable to connect
from a client (such as a PC) as two different users at once. Attempts to connect the sec-
ond user will result in access denied or similar.
If no printer name is specified to printable services, most systems will use the
value of this variable (or lp if this variable is not defined) as the name of the
printer to use. This is not specific to the server, however.
Samba uses PAM for authentication (when presented with a plaintext password), for account
checking (is this account disabled?) and for session management. The degree too which
samba supports PAM is restricted by the limitations of the SMB protocol and the obey pam
restricions smb.conf paramater. When this is set, the following restrictions apply:
o Account Validation: All acccesses to a samba server are checked against PAM to see if
the account is vaild, not disabled and is permitted to login at this time. This also
applies to encrypted logins.
o Session Management: When not using share level secuirty, users must pass PAM's session
checks before access is granted. Note however, that this is bypassed in share level
secuirty. Note also that some older pam configuration files may need a line added for
This man page is correct for version 2.2 of the Samba suite.
One of the common causes of difficulty when installing Samba and SWAT is the existsnece of
some type of firewall or port filtering software on the Samba server. Make sure that the
appropriate ports outlined in this man page are available on the server and are not cur-
rently being blocked by some type of security software such as iptables or "port sentry".
For more troubleshooting information, refer to the additional documentation included in
the Samba distribution.
Most diagnostics issued by the server are logged in a specified log file. The log file
name is specified at compile time, but may be overridden on the command line.
The number and nature of diagnostics available depends on the debug level used by the
server. If you have problems, set the debug level to 3 and peruse the log files.
Most messages are reasonably self-explanatory. Unfortunately, at the time this man page
was created, there are too many diagnostics available in the source code to warrant
describing each and every diagnostic. At this stage your best bet is still to grep the
source code and inspect the conditions that gave rise to the diagnostics you are seeing.
Sending the smbd a SIGHUP will cause it to reload its smb.conf configuration file within a
short period of time.
To shut down a user's smbd process it is recommended that SIGKILL (-9) NOT be used, except
as a last resort, as this may leave the shared memory area in an inconsistent state. The
safe way to terminate an smbd is to send it a SIGTERM (-15) signal and wait for it to die
on its own.
The debug log level of smbd may be raised or lowered using smbcontrol(1)
program (SIGUSR[1|2] signals are no longer used in Samba 2.2). This is to allow transient
problems to be diagnosed, whilst still running at a normally low log level.
Note that as the signal handlers send a debug write, they are not re-entrant in smbd. This
you should wait until smbd is in a state of waiting for an incoming SMB before issuing
them. It is possible to make the signal handlers safe by un-blocking the signals before
the select call and re-blocking them after, however this would affect performance.
hosts_access(5), inetd(8), nmbd(8) smb.conf(5)
and the Internet RFC's rfc1001.txt, rfc1002.txt. In addition the CIFS (formerly SMB)
specification is available as a link from the Web page http://samba.org/cifs/
The original Samba software and related utilities were created by Andrew Tridgell. Samba
is now developed by the Samba Team as an Open Source project similar to the way the Linux
kernel is developed.
The original Samba man pages were written by Karl Auer. The man page sources were con-
verted to YODL format (another excellent piece of Open Source software, available at
ftp://ftp.icce.rug.nl/pub/unix/ <URL:ftp://ftp.icce.rug.nl/pub/unix/>) and updated for the
Samba 2.0 release by Jeremy Allison. The conversion to DocBook for Samba 2.2 was done by
19 November 2002 SMBD(8)