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dropbear

dropbear

Section: Maintenance Commands (8)
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NAME

dropbear - lightweight SSH2 server  

SYNOPSIS

dropbear [-FEmwsgjki] [-b banner] [-d dsskey] [-r rsakey] [-p port]  

DESCRIPTION

dropbear is a SSH 2 server designed to be small enough to be used in small memory environments, while still being functional and secure enough for general use.  

OPTIONS

-b banner
bannerfile. Display the contents of the file banner before user login (default: none).
-d dsskey
dsskeyfile. Use the contents of the file dsskey for the DSS host key (default: /etc/dropbear/dropbear_dss_host_key). Note that some SSH implementations use the term "DSA" rather than "DSS", they mean the same thing. This file is generated with dropbearkey(8).
-r rsakey
rsakeyfile. Use the contents of the file rsakey for the rsa host key (default: /etc/dropbear/dropbear_rsa_host_key). This file is generated with dropbearkey(8).
-F
Don't fork into background.
-E
Log to standard error rather than syslog.
-m
Don't display the message of the day on login.
-w
Disallow root logins.
-s
Disable password logins.
-g
Disable password logins for root.
-j
Disable local port forwarding.
-k
Disable remote port forwarding.
-p [address:]port
Listen on specified address and TCP port. If just a port is given listen on all addresses. up to 10 can be specified (default 22 if none specified).
-i
Service program mode. Use this option to run dropbear under TCP/IP servers like inetd, tcpsvd, or tcpserver. In program mode the -F option is implied, and -p options are ignored.
-P pidfile
Specify a pidfile to create when running as a daemon. If not specified, the default is /var/run/dropbear.pid
-a
Allow remote hosts to connect to forwarded ports.
-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.
-I idle_timeout
Disconnect the session if no traffic is transmitted or received for idle_timeout seconds.
 

FILES

Authorized Keys

~/.ssh/authorized_keys can be set up to allow remote login with a RSA or DSS key. Each line is of the form

[restrictions] ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIgAsp... [comment]

and can be extracted from a Dropbear private host key with "dropbearkey -y". This is the same format as used by OpenSSH, though the restrictions are a subset (keys with unknown restrictions are ignored). Restrictions are comma separated, with double quotes around spaces in arguments. Available restrictions are:

no-port-forwarding
Don't allow port forwarding for this connection

no-agent-forwarding
Don't allow agent forwarding for this connection

no-X11-forwarding
Don't allow X11 forwarding for this connection

no-pty
Disable PTY allocation. Note that a user can still obtain most of the same functionality with other means even if no-pty is set.

command=forced_command
Disregard the command provided by the user and always run forced_command.

The authorized_keys file and its containing ~/.ssh directory must only be writable by the user, otherwise Dropbear will not allow a login using public key authentication.

Host Key Files

Host key files are read at startup from a standard location, by default /etc/dropbear/dropbear_dss_host_key and /etc/dropbear/dropbear_rsa_host_key or specified on the commandline with -d or -r. These are of the form generated by dropbearkey.

Message Of The Day

By default the file /etc/motd will be printed for any login shell (unless disabled at compile-time). This can also be disabled per-user by creating a file ~/.hushlogin .

 

AUTHOR

Matt Johnston (matt@ucc.asn.au).
Gerrit Pape (pape@smarden.org) wrote this manual page.  

SEE ALSO

dropbearkey(8), dbclient(1)

http://matt.ucc.asn.au/dropbear/dropbear.html


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
FILES
AUTHOR
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 22:01:33 GMT, April 16, 2011