smbpasswd - change a user's SMB password
When run by root:
smbpasswd [ options ] [ username ] [ password ]
smbpasswd [ options ] [ password ]
This tool is part of the Samba suite.
The smbpasswd program has several different functions, depending on
whether it is run by the root user or not. When run as a normal user it
allows the user to change the password used for their SMB sessions on
any machines that store SMB passwords.
By default (when run with no arguments) it will attempt to change the
current user's SMB password on the local machine. This is similar to
the way the passwd(1) program works. smbpasswd differs from how the
passwd program works however in that it is not setuid root but works in
a client-server mode and communicates with a locally running smbd(8).
As a consequence in order for this to succeed the smbd daemon must be
running on the local machine. On a UNIX machine the encrypted SMB pass-
words are usually stored in the smbpasswd(5) file.
When run by an ordinary user with no options. smbpasswd will prompt
them for their old SMB password and then ask them for their new pass-
word twice, to ensure that the new password was typed correctly. No
passwords will be echoed on the screen whilst being typed. If you have
a blank SMB password (specified by the string "NO PASSWORD" in the smb-
passwd file) then just press the <Enter> key when asked for your old
smbpasswd can also be used by a normal user to change their SMB pass-
word on remote machines, such as Windows NT Primary Domain Controllers.
See the (-r) and -U options below.
When run by root, smbpasswd allows new users to be added and deleted in
the smbpasswd file, as well as allows changes to the attributes of the
user in this file to be made. When run by root, smbpasswd accesses the
local smbpasswd file directly, thus enabling changes to be made even if
smbd is not running.
smbpasswd can also be used to retrieve the SIDs related to previous
incarnations of this server on the same machine, as well as set the SID
of this domain. This is needed in those cases when the admin changes
the NetBIOS or DNS name of the server without realizing that doing so
will change the SID of the server as well. See the -W and -X options
-L Run the smbpasswd command in local mode. This allows a non-root
user to specify the root-only options. This is used mostly in
test environments where a non-root user needs to make changes to
the local smbpasswd file. The smbpasswd file must have
read/write permissions for the user running the command.
-h This option prints the help string for smbpasswd.
-c smb.conf file
This option specifies that the configuration file specified
should be used instead of the default value specified at compile
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 smbpasswd. At level 0, only criti-
cal errors and serious warnings will be logged.
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.
-r remote machine name
This option allows a user to specify what machine they wish to
change their password on. Without this parameter smbpasswd
defaults to the local host. The remote machine name is the Net-
BIOS name of the SMB/CIFS server to contact to attempt the pass-
word change. This name is resolved into an IP address using the
standard name resolution mechanism in all programs of the Samba
suite. See the -R name resolve order parameter for details on
changing this resolving mechanism.
The username whose password is changed is that of the current
UNIX logged on user. See the -U username parameter for details
on changing the password for a different username.
Note that if changing a Windows NT Domain password the remote
machine specified must be the Primary Domain Controller for the
domain (Backup Domain Controllers only have a read-only copy of
the user account database and will not allow the password
Note that Windows 95/98 do not have a real password database so
it is not possible to change passwords specifying a Win95/98
machine as remote machine target.
-s This option causes smbpasswd to be silent (i.e. not issue
prompts) and to read its old and new passwords from standard
input, rather than from /dev/tty (like the passwd(1) program
does). This option is to aid people writing scripts to drive
-S This option causes smbpasswd to query a domain controller of the
domain specified by the workgroup parameter in smb.conf and
store the domain SID in the secrets.tdb file as its own machine
SID. This is only useful when configuring a Samba PDC and Samba
BDC, or when migrating from a Windows PDC to a Samba PDC.
The -r options can be used as well to indicate a specific domain
controller which should be contacted. In this case, the domain
SID obtained is the one for the domain to which the remote
-t This option is used to force smbpasswd to change the current
password assigned to the machine trust account when operating in
domain security mode. This is really meant to be used on systems
that only run winbindd Under server installations, smbd handle
the password updates automatically.
This option may only be used in conjunction with the -r option.
When changing a password on a remote machine it allows the user
to specify the user name on that machine whose password will be
changed. It is present to allow users who have different user
names on different systems to change these passwords. The
optional %pass may be used to specify to old password.
In particular, this parameter specifies the username used to
create the machine account when invoked with -j
This option forces the SID S-1-5-21-x-y-z to be the server and
domain SID for the current Samba server. It does this by updat-
ing the appropriate keys in the secrets file.
This option allows the admin to retrieve the SID associated with
a former servername or domain name that this Samba server might
have used. It does this by retrieving the appropriate entry from
the secrets file.
NOTE: The following options are available only when the smbpasswd com-
mand is run as root or in local mode.
-a This option specifies that the username following should be
added to the local smbpasswd file, with the new password typed.
This option is ignored if the username specified already exists
in the smbpasswd file and it is treated like a regular change
password command. Note that the user to be added must already
exist in the system password file (usually /etc/passwd) else the
request to add the user will fail.
-d This option specifies that the username following should be dis-
abled in the local smbpasswd file. This is done by writing a 'D'
flag into the account control space in the smbpasswd file. Once
this is done all attempts to authenticate via SMB using this
username will fail.
If the smbpasswd file is in the 'old' format (pre-Samba 2.0 for-
mat) there is no space in the user's password entry to write
this information and so the user is disabled by writing 'X'
characters into the password space in the smbpasswd file. See
smbpasswd(5) for details on the 'old' and new password file for-
-e This option specifies that the username following should be
enabled in the local smbpasswd file, if the account was previ-
ously disabled. If the account was not disabled this option has
no effect. Once the account is enabled then the user will be
able to authenticate via SMB once again.
If the smbpasswd file is in the 'old' format, then smbpasswd
will prompt for a new password for this user, otherwise the
account will be enabled by removing the 'D' flag from account
control space in the smbpasswd file. See smbpasswd (5) for
details on the 'old' and new password file formats.
-m This option tells smbpasswd that the account being changed is a
MACHINE account. Currently this is used when Samba is being used
as an NT Primary Domain Controller.
-n This option specifies that the username following should have
their password set to null (i.e. a blank password) in the local
smbpasswd file. This is done by writing the string "NO PASSWORD"
as the first part of the first password stored in the smbpasswd
Note that to allow users to logon to a Samba server once the
password has been set to "NO PASSWORD" in the smbpasswd file the
administrator must set the following parameter in the [global]
section of the smb.conf file :
null passwords = yes
This parameter is only available is Samba has been configured to
use the experimental --with-ldapsam option. The -w switch is
used to specify the password to be used with the ldap admin dn
Note that the password is stored in the private/secrets.tdb and
is keyed off of the admin's DN. This means that if the value of
ldap admin dn ever changes, the password will need to be manu-
ally updated as well.
-x This option specifies that the username following should be
deleted from the local smbpasswd file.
This option is used to add a Samba server into a Windows NT
Domain, as a Domain member capable of authenticating user
accounts to any Domain Controller in the same way as a Windows
NT Server. See the security = domain option in the smb.conf(5)
This command can work both with and without the -U parameter.
When invoked with -U, that username (and optional password) are
used to contact the PDC (which must be specified with -r) to
both create a machine account, and to set a password on it.
Alternately, if -U is omitted, Samba will contact its PDC and
attempt to change the password on a pre-existing account.
In order to be used in this way, the Administrator for the Win-
dows NT Domain must have used the program "Server Manager for
Domains" to add the primary NetBIOS name of the Samba server as
a member of the Domain.
After this has been done, to join the Domain invoke smbpasswd
with this parameter. smbpasswd will then look up the Primary
Domain Controller for the Domain (found in the smb.conf file in
the parameter password server and change the machine account
password used to create the secure Domain communication.
Either way, this password is then stored by smbpasswd in a TDB,
writeable only by root, called secrets.tdb
Once this operation has been performed the smb.conf file may be
updated to set the security = domain option and all future
logins to the Samba server will be authenticated to the Windows
Note that even though the authentication is being done to the
PDC all users accessing the Samba server must still have a valid
UNIX account on that machine. The winbindd(8) daemon can be
used to create UNIX accounts for NT users.
-R name resolve order
This option allows the user of smbpasswd to determine what name
resolution services to use when looking up the NetBIOS name of
the host being connected to.
The options are :"lmhosts", "host", "wins" and "bcast". They
cause names to be resolved as follows :
o lmhosts : Lookup an IP address in the Samba lmhosts file. If
the line in lmhosts has no name type attached to the NetBIOS
name (see the lmhosts(5) for details) then any name type
matches for lookup.
o host : Do a standard host name to IP address resolution, using
the system /etc/hosts , NIS, or DNS lookups. This method of
name resolution is operating system dependent. For instance,
on IRIX or Solaris this may be controlled by the /etc/nss-
witch.conf file). Note that this method is only used if the
NetBIOS name type being queried is the 0x20 (server) name
type, otherwise it is ignored.
o wins : Query a name with the IP address listed in the wins
server parameter. If no WINS server has been specified this
method will be ignored.
o bcast : Do a broadcast on each of the known local interfaces
listed in the interfaces parameter. This is the least reliable
of the name resolution methods as it depends on the target
host being on a locally connected subnet.
The default order is lmhosts, host, wins, bcast and without this param-
eter or any entry in the smb.conf file the name resolution methods will
be attempted in this order.
This specifies the username for all of the root only options to
operate on. Only root can specify this parameter as only root
has the permission needed to modify attributes directly in the
local smbpasswd file.
This specifies the new password. If this parameter is specified
you will not be prompted for the new password.
Since smbpasswd works in client-server mode communicating with a local
smbd for a non-root user then the smbd daemon must be running for this
to work. A common problem is to add a restriction to the hosts that may
access the smbd running on the local machine by specifying a allow
hosts or deny hosts entry in the smb.conf file and neglecting to allow
"localhost" access to the smbd.
In addition, the smbpasswd command is only useful if Samba has been set
up to use encrypted passwords. See the file ENCRYPTION.txt in the docs
directory for details on how to do this.
This man page is correct for version 2.2 of the Samba suite.
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
01 February 2003 SMBPASSWD(8)