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dropbear(8)            DragonFly System Manager's Manual           dropbear(8)

NAME
       dropbear - lightweight SSH server

SYNOPSIS
       dropbear [flag arguments] [-b banner] [-r hostkeyfile] [-p
       [address:]port]

DESCRIPTION
       dropbear is a small SSH server

OPTIONS
       -b banner
              bannerfile.  Display the contents of the file banner before user
              login (default: none).

       -r hostkey
              Use the contents of the file hostkey for the SSH hostkey.  This
              file is generated with dropbearkey(1) or automatically with the
              '-R' option. See "Host Key Files" below.

       -R     Generate hostkeys automatically. See "Host Key Files" below.

       -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. 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.

       -V     Print the version

FILES
       Authorized Keys

              ~/.ssh/authorized_keys can be set up to allow remote login with
              a RSA, ECDSA, 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,
              /etc/dropbear/dropbear_rsa_host_key, and
              /etc/dropbear/dropbear_ecdsa_host_key or specified on the
              commandline with -r. These are of the form generated by
              dropbearkey. The -R option can be used to automatically generate
              keys in the default location - keys will be generated after
              startup when the first connection is established. This had the
              benefit that the system /dev/urandom random number source has a
              better chance of being securely seeded.

       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 .

ENVIRONMENT VARIABLES
       Dropbear sets the standard variables USER, LOGNAME, HOME, SHELL, PATH,
       and TERM.

       The variables below are set for sessions as appropriate.

       SSH_TTY
              This is set to the allocated TTY if a PTY was used.

       SSH_CONNECTION
              Contains "<remote_ip> <remote_port> <local_ip> <local_port>".

       DISPLAY
              Set X11 forwarding is used.

       SSH_ORIGINAL_COMMAND
              If a 'command=' authorized_keys option was used, the original
              command is specified in this variable. If a shell was requested
              this is set to an empty value.

       SSH_AUTH_SOCK
              Set to a forwarded ssh-agent connection.

NOTES
       Dropbear only supports SSH protocol version 2.

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

SEE ALSO
       dropbearkey(1), dbclient(1), dropbearconvert(1)

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

                                                                   dropbear(8)