SMBD(8)SMBD(8)NAMEsmbd - server to provide SMB/CIFS services to clients
SYNOPSISsmbd [ -D ] [ -a ] [ -o ] [ -P ] [ -h ] [ -V ] [ -d
<debug level> ] [ -l <log file> ] [ -p <port number> ]
[ -O <socket option> ] [ -s <configuration file> ]
DESCRIPTION
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 LanManager clients. These
include MSCLIENT 3.0 for DOS, Windows for Workgroups, Win-
dows 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
smb.conf(5) services, but will concentrate on the adminis-
trative aspects of running the server.
Please note that there are significant security implica-
tions to running this server, and the smb.conf(5) manpage
should be regarded as mandatory reading before proceeding
with installation.
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 dur-
ing 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.
Reloading the configuration file will not affect connec-
tions to any service that is already established. Either
the user will have to disconnect from the service, or smbd
killed and restarted.
OPTIONS-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.
09 July 2001 1
SMBD(8)SMBD(8)-a If this parameter is specified, each new connection
will append log messages to the log file. This is
the default.
-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 seri-
ous warnings will be logged. Level 1 is a reason-
able level for day to day running - it generates a
small amount of information about operations car-
ried out.
Levels above 1 will generate considerable amounts
of log data, and should only be used when investi-
gating a problem. Levels above 3 are designed for
use only by developers and generate HUGE amounts of
log data, most of which is extremely cryptic.
Note that specifying this parameter here will over-
ride the log levelfile.
-l <log file>
If specified, log file specifies a log filename
into which informational and debug messages from
the running server will be logged. The log file
generated is never removed by the server although
its size may be controlled by the max log size
option in the smb.conf(5)file. The default log
file name 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.
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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 situa-
tion.
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 ser-
vices 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 descrip-
tions of all the services that the server is to
provide. See smb.conf(5)for more information. The
default configuration file name is determined at
compile time.
FILES
/etc/inetd.conf
If the server is to be run by the inetd meta-dae-
mon, this file must contain suitable startup infor-
mation for the meta-daemon. See the section INSTAL-
LATION below.
/etc/rc
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 section INSTALLA-
TION below.
/etc/services
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 section INSTAL-
LATION below.
/usr/local/samba/lib/smb.conf
This is the default location of the smb.conf server
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configuration file. Other common places that sys-
tems install this file are /usr/samba/lib/smb.conf
and /etc/smb.conf.
This file describes all the services the server is
to make available to clients. See smb.conf(5)for
more information.
LIMITATIONS
On some systems smbd cannot change uid back to root after
a setuid() call. Such systems are called trapdoor uid sys-
tems. 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 second user will
result in access denied or similar.
ENVIRONMENTVARIABLES
PRINTER
If no printer name is specified to printable ser-
vices, 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 spe-
cific to the server, however.
INSTALLATION
The location of the server and its support files is a mat-
ter for individual system administrators. The following
are thus suggestions only.
It is recommended that the server software be installed
under the /usr/local/samba/ hierarchy, in a directory
readable by all, writeable only by root. The server pro-
gram itself should be executable by all, as users may wish
to run the server themselves (in which case it will of
course run with their privileges). The server should NOT
be setuid. On some systems it may be worthwhile to make
smbd setgid to an empty group. This is because some sys-
tems may have a security hole where daemon processes that
become a user can be attached to with a debugger. Making
the smbd file setgid to an empty group may prevent this
hole from being exploited. This security hole and the sug-
gested fix has only been confirmed on old versions (pre-
kernel 2.0) of Linux at the time this was written. It is
possible that this hole only exists in Linux, as testing
on other systems has thus far shown them to be immune.
The server log files should be put in a directory readable
and writeable only by root, as the log files may contain
sensitive information.
The configuration file should be placed in a directory
readable and writeable only by root, as the configuration
file controls security for the services offered by the
server. The configuration file can be made readable by all
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if desired, but this is not necessary for correct opera-
tion of the server and is not recommended. A sample con-
figuration file smb.conf.sample is supplied with the
source to the server - this may be renamed to smb.conf and
modified to suit your needs.
The remaining notes will assume the following:
o smbd (the server program) installed in
/usr/local/samba/bin
o smb.conf (the configuration file) installed in
/usr/local/samba/lib
o log files stored in /var/adm/smblogs
The server may be run either as a daemon by users or at
startup, or it may be run from a meta-daemon such as inetd
upon request. If run as a daemon, the server will always
be ready, so starting sessions will be faster. If run from
a meta-daemon some memory will be saved and utilities such
as the tcpd TCP-wrapper may be used for extra security.
For serious use as file server it is recommended that smbd
be run as a daemon.
When you've decided, continue with either
o RUNNING THE SERVER AS A DAEMON or
o RUNNING THE SERVER ON REQUEST.
RUNNING THE SERVER AS A DAEMON
To run the server as a daemon from the command line, sim-
ply put the -D option on the command line. There is no
need to place an ampersand at the end of the command line
- the -D option causes the server to detach itself from
the tty anyway.
Any user can run the server as a daemon (execute permis-
sions permitting, of course). This is useful for testing
purposes, and may even be useful as a temporary substitute
for something like ftp. When run this way, however, the
server will only have the privileges of the user who ran
it.
To ensure that the server is run as a daemon whenever the
machine is started, and to ensure that it runs as root so
that it can serve multiple clients, you will need to mod-
ify the system startup files. Wherever appropriate (for
example, in /etc/rc), insert the following line, substi-
tuting port number, log file location, configuration file
location and debug level as desired:
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SMBD(8)SMBD(8)
/usr/local/samba/bin/smbd -D-l /var/adm/smblogs/log -s
/usr/local/samba/lib/smb.conf
(The above should appear in your initialization script as
a single line. Depending on your terminal characteristics,
it may not appear that way in this man page. If the above
appears as more than one line, please treat any newlines
or indentation as a single space or TAB character.)
If the options used at compile time are appropriate for
your system, all parameters except -D may be omitted. See
the section OPTIONS above.
RUNNING THE SERVER ON REQUEST
If your system uses a meta-daemon such as inetd , you can
arrange to have the smbd server started whenever a process
attempts to connect to it. This requires several changes
to the startup files on the host machine. If you are
experimenting as an ordinary user rather than as root, you
will need the assistance of your system administrator to
modify the system files.
You will probably want to set up the NetBIOS name server
nmbdat the same time as smbd. To do this refer to the man
page for nmbd(8)
First, ensure that a port is configured in the file
/etc/services. The well-known port 139 should be used if
possible, though any port may be used.
Ensure that a line similar to the following is in
/etc/services:
netbios-ssn 139/tcp
Note for NIS/YP users - you may need to rebuild the NIS
service maps rather than alter your local /etc/services
file.
Next, put a suitable line in the file /etc/inetd.conf (in
the unlikely event that you are using a meta-daemon other
than inetd, you are on your own). Note that the first item
in this line matches the service name in /etc/services .
Substitute appropriate values for your system in this line
(see inetd(8)):
netbios-ssn stream tcp nowait root
/usr/local/samba/bin/smbd -d1 -l/var/adm/smblogs/log
-s/usr/local/samba/lib/smb.conf
(The above should appear in /etc/inetd.conf as a single
line. Depending on your terminal characteristics, it may
not appear that way in this man page. If the above appears
as more than one line, please treat any newlines or
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SMBD(8)SMBD(8)
indentation as a single space or TAB character.)
Note that there is no need to specify a port number here,
even if you are using a non-standard port number.
Lastly, edit the configuration file to provide suitable
services. To start with, the following two services should
be all you need:
[homes]
writeable = yes
[printers]
writeable = no
printable = yes
path = /tmp
public = yes
This will allow you to connect to your home directory and
print to any printer supported by the host (user privi-
leges permitting).
PAM INTERACTION
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 configu-
ration files may need a line added for session support.
TESTING THE INSTALLATION
If running the server as a daemon, execute it before pro-
ceeding. If using a meta-daemon, either restart the system
or kill and restart the meta-daemon. Some versions of
inetd will reread their configuration tables if they
receive a HUP signal.
If your machine's name is fred and your name is mary, you
should now be able to connect to the service \\fred\mary.
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To properly test and experiment with the server, we recom-
mend using the smbclient program (see smbclient(1)) and
also going through the steps outlined in the file DIAGNO-
SIS.txt in the docs/ directory of your Samba installation.
VERSION
This man page is correct for version 2.2 of the Samba
suite.
DIAGNOSTICS
Most diagnostics issued by the server are logged in a
specified log file. The log file name is specified at com-
pile 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. Unfortu-
nately, at the time this man page was created, there are
too many diagnostics available in the source code to war-
rant 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.
SIGNALS
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 by sending it a
SIGUSR1 (kill -USR1 <smbd-pid>) and lowered by sending it
a SIGUSR2 (kill -USR2 <smbd-pid> ). This is to allow tran-
sient 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 perfor-
mance.
SEE ALSOhosts_access(5), inetd(8), nmbd(8), smb.conf(5) , smb-
client(1) , and the Internet RFC's rfc1001.txt,
rfc1002.txt. In addition the CIFS (formerly SMB)
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specification is available as a link from the Web page
http://samba.org/cifs/ <URL:http://samba.org/cifs/>.
AUTHOR
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 converted to YODL format
(another excellent piece of Open Source software, avail-
able 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 Gerald Carter
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