NAME¶
dbclient - lightweight SSH client
SYNOPSIS¶
dbclient [-Tt] [-p
port] [-i id] [-L
l:h:r] [-R l:h:r] [-l user]
host [
command]
dbclient [
args ]
[user1]@host1[^port1],[user2]@host2[^port2],...
DESCRIPTION¶
dbclient is a small SSH client
If compiled with zlib support and if the server supports it, dbclient will
always use compression.
OPTIONS¶
- -p port
- Connect to port on the remote host. Alternatively a port can be
specified as hostname^port. Default is 22.
- -i idfile
- Identity file. Read the identity key from file idfile (multiple
allowed). This file is created with dropbearkey(1) or converted from
OpenSSH with dropbearconvert(1).
- -L
[listenaddress]:listenport:host:port
- Local port forwarding. Forward the port listenport on the local
host through the SSH connection to port port on the host
host.
- -R
[listenaddress]:listenport:host:port
- Remote port forwarding. Forward the port listenport on the remote
host through the SSH connection to port port on the host
host.
- -l user
- Username. Login as user on the remote host.
- -t
- Allocate a PTY.
- -T
- Don't allocate a PTY.
- -N
- Don't request a remote shell or run any commands. Any command arguments
are ignored.
- -f
- Fork into the background after authentication. A command argument (or -N)
is required. This is useful when using password authentication.
- -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.
- -y
- Always accept hostkeys if they are unknown. If a hostkey mismatch occurs
the connection will abort as normal. If specified a second time no host
key checking is performed at all, this is usually undesirable.
- -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.
- -W windowsize
- 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.
- -K timeout_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. If no response is received for 3 consecutive
keepalives the connection will be closed.
- -I idle_timeout
- Disconnect the session if no traffic is transmitted or received for
idle_timeout seconds.
- -J proxy_command
- Use the standard input/output of the program proxy_command rather
than using a normal TCP connection. A hostname should be still be
provided, as this is used for comparing saved hostkeys.
- -B endhost:endport
- "Netcat-alike" mode, where Dropbear will connect to the given
host, then create a forwarded connection to endhost. This will then
be presented as dbclient's standard input/output.
- -c cipherlist
- Specify a comma separated list of ciphers to enable. Use -c help to
list possibilities.
- -m MAClist
- Specify a comma separated list of authentication MACs to enable. Use -m
help to list possibilities.
- -s
- The specified command will be requested as a subsystem, used for sftp.
Dropbear doesn't implement sftp itself but the OpenSSH sftp client can be
used eg sftp -S dbclient user@host
- -V
- Print the version
MULTI-HOP¶
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 hash (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.
ESCAPE CHARACTERS¶
Typing a newline followed by the key sequence
~. (tilde, dot) will
terminate a connection. The sequence
~^Z (tilde, ctrl-z) will
background the connection. This behaviour only applies when a PTY is used.
ENVIRONMENT¶
- DROPBEAR_PASSWORD
- 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.
- SSH_ASKPASS
- 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 set.
AUTHOR¶
Matt Johnston (matt@ucc.asn.au).
Mihnea Stoenescu wrote initial Dropbear client support
Gerrit Pape (pape@smarden.org) wrote this manual page.
SEE ALSO¶
dropbear(8),
dropbearkey(1)
https://matt.ucc.asn.au/dropbear/dropbear.html