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, 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 smb.conf(5)
. 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 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 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. Reloading
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 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.
-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 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 cryptic.
Note that specifying this parameter here will
override 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.
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 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-daemon, this file
must contain suitable startup information for the
meta-daemon. See the section INSTALLATION 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 INSTALLATION
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 INSTALLATION below.
/usr/local/samba/lib/smb.conf
This is the default location of the
smb.conf
server configuration file. Other common places that systems
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 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
second user will result in access denied or
similar.
ENVIRONMENTVARIABLES
PRINTER
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.
INSTALLATION
The location of the server and its support files
is a matter 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
program 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 systems 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 suggested
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 if desired, but
this is not necessary for correct operation of the server and is
not recommended. A sample configuration 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:
bu
smbd (the server program)
installed in /usr/local/samba/bin
bu
smb.conf (the configuration
file) installed in /usr/local/samba/lib
bu
log files stored in /var/adm/smblogs
.PP
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
bu
RUNNING THE SERVER AS A DAEMON or
bu
RUNNING THE SERVER ON REQUEST.
RUNNING THE SERVER AS A DAEMON
To run the server as a daemon from the command
line, simply 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
permissions 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 modify
the system startup files. Wherever appropriate (for example, in
/etc/rc), insert the following line,
substituting port number, log file location, configuration file
location and debug level as desired:
(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)):
(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 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 privileges
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:
bu
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.
bu
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 session support.
TESTING THE INSTALLATION
If running the server as a daemon, execute it before
proceeding. 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.
To properly test and experiment with the server, we
recommend using the smbclient program (see
smbclient(1))
and also going through the steps outlined in the file
DIAGNOSIS.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 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.
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 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.
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, 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 Gerald Carter
