3 dropbear \- lightweight SSH server
6 [\fIflag arguments\fR] [\-b
9 .I hostkeyfile\fR] [\-p [\fIaddress\fR:]\fIport\fR]
17 Display the contents of the file
19 before user login (default: none).
22 Use the contents of the file
25 This file is generated with
27 or automatically with the '-R' option. See "Host Key Files" below.
30 Generate hostkeys automatically. See "Host Key Files" below.
33 Don't fork into background.
36 Log to standard error rather than syslog.
39 Don't display the message of the day on login.
45 Disable password logins.
48 Disable password logins for root.
51 Disable local port forwarding.
54 Disable remote port forwarding.
56 .B \-p\fR [\fIaddress\fR:]\fIport
61 If just a port is given listen
63 up to 10 can be specified (default 22 if none specified).
67 Use this option to run
69 under TCP/IP servers like inetd, tcpsvd, or tcpserver.
70 In program mode the \-F option is implied, and \-p options are ignored.
73 Specify a pidfile to create when running as a daemon. If not specified, the
74 default is /var/run/dropbear.pid
77 Allow remote hosts to connect to forwarded ports.
80 Specify the per-channel receive window buffer size. Increasing this
81 may improve network performance at the expense of memory use. Use -h to see the
84 .B \-K \fItimeout_seconds
85 Ensure that traffic is transmitted at a certain interval in seconds. This is
86 useful for working around firewalls or routers that drop connections after
87 a certain period of inactivity. The trade-off is that a session may be
88 closed if there is a temporary lapse of network connectivity. A setting
89 if 0 disables keepalives. If no response is received for 3 consecutive keepalives the connection will be closed.
91 .B \-I \fIidle_timeout
92 Disconnect the session if no traffic is transmitted or received for \fIidle_timeout\fR seconds.
102 ~/.ssh/authorized_keys can be set up to allow remote login with a RSA,
104 key. Each line is of the form
106 [restrictions] ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIgAsp... [comment]
108 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).
109 Restrictions are comma separated, with double quotes around spaces in arguments.
110 Available restrictions are:
113 .B no-port-forwarding
114 Don't allow port forwarding for this connection
117 .B no-agent-forwarding
118 Don't allow agent forwarding for this connection
122 Don't allow X11 forwarding for this connection
126 Disable PTY allocation. Note that a user can still obtain most of the
127 same functionality with other means even if no-pty is set.
130 .B command=\fR"\fIforced_command\fR"
131 Disregard the command provided by the user and always run \fIforced_command\fR.
133 The authorized_keys file and its containing ~/.ssh directory must only be
134 writable by the user, otherwise Dropbear will not allow a login using public
140 Host key files are read at startup from a standard location, by default
141 /etc/dropbear/dropbear_dss_host_key, /etc/dropbear/dropbear_rsa_host_key, and
142 /etc/dropbear/dropbear_ecdsa_host_key
143 or specified on the commandline with -r. These are of the form generated
144 by dropbearkey. The -R option can be used to automatically generate keys
145 in the default location - keys will be generated after startup when the first
146 connection is established. This had the benefit that the system /dev/urandom
147 random number source has a better chance of being securely seeded.
152 By default the file /etc/motd will be printed for any login shell (unless
153 disabled at compile-time). This can also be disabled per-user
154 by creating a file ~/.hushlogin .
156 .SH ENVIRONMENT VARIABLES
157 Dropbear sets the standard variables USER, LOGNAME, HOME, SHELL, PATH, and TERM.
159 The variables below are set for sessions as appropriate.
163 This is set to the allocated TTY if a PTY was used.
167 Contains "<remote_ip> <remote_port> <local_ip> <local_port>".
171 Set X11 forwarding is used.
174 .B SSH_ORIGINAL_COMMAND
175 If a 'command=' authorized_keys option was used, the original command is specified
176 in this variable. If a shell was requested this is set to an empty value.
180 Set to a forwarded ssh-agent connection.
183 Dropbear only supports SSH protocol version 2.
186 Matt Johnston (matt@ucc.asn.au).
188 Gerrit Pape (pape@smarden.org) wrote this manual page.
190 dropbearkey(1), dbclient(1), dropbearconvert(1)
192 https://matt.ucc.asn.au/dropbear/dropbear.html