view dbclient.1 @ 588:a55b97f5a485

Fix bug in primality testing, see Exact effects of the bug are uncertain.
author Matt Johnston <>
date Wed, 21 Jul 2010 13:33:07 +0000
parents 52d7301e46bd
children a415c5b71420
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.TH dbclient 1
dbclient \- lightweight SSH2 client
.B dbclient
[\-Tt] [\-p
.I port\fR] [\-i
.I id\fR] [\-L
.I l\fR:\fIh\fR:\fIr\fR] [\-R
.I l\fR:\fIh\fR:\fIr\fR] [\-l
.IR user ]
.I host
.RI [ command ]

.B dbclient
.I args ]
.I [user1]@host1[/port1],[user2]@host2[/port2],...

.B dbclient
is a SSH 2 client designed to be small enough to be used in small memory
environments, while still being functional and secure enough for general use.
.B \-p \fIport
Remote port.
Connect to port
.I port
on the remote host.
Default is 22.
.B \-i \fIidfile
Identity file.
Read the identity from file
.I idfile
(multiple allowed).
.B \-L \fIlistenport\fR:\fIhost\fR:\fIport\fR
Local port forwarding.
Forward the port
.I listenport
on the local host through the SSH connection to port
.I port
on the host
.IR host .
.B \-R \fIlistenport\fR:\fIhost\fR:\fIport\fR
Remote port forwarding.
Forward the port
.I listenport
on the remote host through the SSH connection to port
.I port
on the host
.IR host .
.B \-l \fIuser
Login as
.I user
on the remote host.
.B \-t
Allocate a pty.
.B \-T
Don't allocate a pty.
.B \-N
Don't request a remote shell or run any commands. Any command arguments are ignored.
.B \-f
Fork into the background after authentication. A command argument (or -N) is required.
This is useful when using password authentication.
.B \-g
Allow non-local hosts to connect to forwarded ports. Applies to -L and -R
forwarded ports, though remote connections to -R forwarded ports may be limited
by the ssh server.
.B \-y
Always accept hostkeys if they are unknown. If a hostkey mismatch occurs the
connection will abort as normal.
.B \-A
Forward agent connections to the remote host. dbclient will use any
OpenSSH-style agent program if available ($SSH_AUTH_SOCK will be set) for
public key authentication.  Forwarding is only enabled if -A is specified.
.B \-W \fIwindowsize
Specify the per-channel receive window buffer size. Increasing this 
may improve network performance at the expense of memory use. Use -h to see the
default buffer size.
.B \-K \fItimeout_seconds
Ensure that traffic is transmitted at a certain interval in seconds. This is
useful for working around firewalls or routers that drop connections after
a certain period of inactivity. The trade-off is that a session may be
closed if there is a temporary lapse of network connectivity. A setting
if 0 disables keepalives.
.B \-I \fIidle_timeout
Disconnect the session if no traffic is transmitted or received for \fIidle_timeout\fR seconds.
.B \-J \fIproxy_command
Use the standard input/output of the program \fIproxy_command\fR rather than using
a normal TCP connection. A hostname should be still be provided, as this is used for
comparing saved hostkeys.
.B \-B \fIendhost:endport
"Netcat-alike" mode, where Dropbear will connect to the given host, then create a
forwarded connection to \fIendhost\fR. This will then be presented as dbclient's
standard input/output.

Dropbear will also allow multiple "hops" to be specified, separated by commas. In
this case a connection will be made to the first host, then a TCP forwarded 
connection will be made through that to the second host, and so on. Hosts other than
the final destination will not see anything other than the encrypted SSH stream. 
A port for a host can be specified with a slash (eg matt@martello/44 ).
This syntax can also be used with scp or rsync (specifying dbclient as the 
ssh/rsh command). A file can be "bounced" through multiple SSH hops, eg

scp -S dbclient matt@martello,root@wrt,canyons:/tmp/dump .

Note that hostnames are resolved by the prior hop (so "canyons" would be resolved by the host "wrt")
in the example above, the same way as other -L TCP forwarded hosts are. Host keys are 
checked locally based on the given hostname.

A password to use for remote authentication can be specified in the environment
variable DROPBEAR_PASSWORD. Care should be taken that the password is not
exposed to other users on a multi-user system, or stored in accessible files.
dbclient can use an external program to request a password from a user.
SSH_ASKPASS should be set to the path of a program that will return a password
on standard output. This program will only be used if either DISPLAY is set and
standard input is not a TTY, or the environment variable SSH_ASKPASS_ALWAYS is
Matt Johnston ([email protected]).
Mihnea Stoenescu wrote initial Dropbear client support
Gerrit Pape ([email protected]) wrote this manual page.
dropbear(8), dropbearkey(8)