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1.ig \" -*- nroff -*- 1.ig \" -*- nroff -*-
2Copyright (c) 1999 Philip Hands Computing <http://www.hands.com/> 2Copyright (c) 1999-2013 hands.com Ltd. <http://hands.com/>
3 3
4Permission is granted to make and distribute verbatim copies of 4Redistribution and use in source and binary forms, with or without
5this manual provided the copyright notice and this permission notice 5modification, are permitted provided that the following conditions
6are preserved on all copies. 6are met:
71. Redistributions of source code must retain the above copyright
8 notice, this list of conditions and the following disclaimer.
92. Redistributions in binary form must reproduce the above copyright
10 notice, this list of conditions and the following disclaimer in the
11 documentation and/or other materials provided with the distribution.
7 12
8Permission is granted to copy and distribute modified versions of this 13THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
9manual under the conditions for verbatim copying, provided that the 14IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
10entire resulting derived work is distributed under the terms of a 15OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
11permission notice identical to this one. 16IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
12 17INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
13Permission is granted to copy and distribute translations of this 18NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
14manual into another language, under the above conditions for modified 19DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
15versions, except that this permission notice may be included in 20THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
16translations approved by the Free Software Foundation instead of in 21(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
17the original English. 22THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
18.. 23..
19.TH SSH-COPY-ID 1 "14 November 1999" "OpenSSH" 24.Dd $Mdocdate: June 17 2010 $
20.SH NAME 25.Dt SSH-COPY-ID 1
21ssh-copy-id \- install your public key in a remote machine's authorized_keys 26.Os
22.SH SYNOPSIS 27.Sh NAME
23.B ssh-copy-id [-i [identity_file]] 28.Nm ssh-copy-id
24.I "[user@]machine" 29.Nd use locally available keys to authorise logins on a remote machine
30.Sh SYNOPSIS
31.Nm
32.Op Fl n
33.Op Fl i Op Ar identity_file
34.Op Fl p Ar port
35.Op Fl o Ar ssh_option
36.Op Ar user Ns @ Ns
37.Ar hostname
38.Nm
39.Fl h | Fl ?
25.br 40.br
26.SH DESCRIPTION 41.Sh DESCRIPTION
27.BR ssh-copy-id 42.Nm
28is a script that uses ssh to log into a remote machine and 43is a script that uses
29append the indicated identity file to that machine's 44.Xr ssh 1
30.B ~/.ssh/authorized_keys 45to log into a remote machine (presumably using a login password,
31file. 46so password authentication should be enabled, unless you've done some
32.PP 47clever use of multiple identities). It assembles a list of one or more
33If the 48fingerprints (as described below) and tries to log in with each key, to
34.B -i 49see if any of them are already installed (of course, if you are not using
35option is given then the identity file (defaults to 50.Xr ssh-agent 1
36.BR ~/.ssh/id_rsa.pub ) 51this may result in you being repeatedly prompted for pass-phrases).
37is used, regardless of whether there are any keys in your 52It then assembles a list of those that failed to log in, and using ssh,
38.BR ssh-agent . 53enables logins with those keys on the remote server. By default it adds
39Otherwise, if this: 54the keys by appending them to the remote user's
40.PP 55.Pa ~/.ssh/authorized_keys
41.B " ssh-add -L" 56(creating the file, and directory, if necessary). It is also capable
42.PP 57of detecting if the remote system is a NetScreen, and using its
43provides any output, it uses that in preference to the identity file. 58.Ql set ssh pka-dsa key ...
44.PP 59command instead.
45If the 60.Pp
46.B -i 61The options are as follows:
47option is used, or the 62.Bl -tag -width Ds
48.B ssh-add 63.It Fl i Ar identity_file
49produced no output, then it uses the contents of the identity 64Use only the key(s) contained in
50file. Once it has one or more fingerprints (by whatever means) it 65.Ar identity_file
51uses ssh to append them to 66(rather than looking for identities via
52.B ~/.ssh/authorized_keys 67.Xr ssh-add 1
53on the remote machine (creating the file, and directory, if necessary.) 68or in the
54 69.Ic default_ID_file ) .
55.SH NOTES 70If the filename does not end in
56This program does not modify the permissions of any 71.Pa .pub
57pre-existing files or directories. Therefore, if the remote 72this is added. If the filename is omitted, the
58.B sshd 73.Ic default_ID_file
59has 74is used.
60.B StrictModes 75.Pp
61set in its 76Note that this can be used to ensure that the keys copied have the
62configuration, then the user's home, 77comment one prefers and/or extra options applied, by ensuring that the
63.B ~/.ssh 78key file has these set as preferred before the copy is attempted.
64folder, and 79.It Fl n
65.B ~/.ssh/authorized_keys 80do a dry-run. Instead of installing keys on the remote system simply
66file may need to have group writability disabled manually, e.g. via 81prints the key(s) that would have been installed.
67 82.It Fl h , Fl ?
68.B " chmod go-w ~ ~/.ssh ~/.ssh/authorized_keys" 83Print Usage summary
69 84.It Fl p Ar port , Fl o Ar ssh_option
70on the remote machine. 85These two options are simply passed through untouched, along with their
71 86argument, to allow one to set the port or other
72.SH "SEE ALSO" 87.Xr ssh 1
73.BR ssh (1), 88options, respectively.
74.BR ssh-agent (1), 89.Pp
75.BR sshd (8) 90Rather than specifying these as command line options, it is often better to use (per-host) settings in
91.Xr ssh 1 Ns 's
92configuration file:
93.Xr ssh_config 5 .
94.El
95.Pp
96Default behaviour without
97.Fl i ,
98is to check if
99.Ql ssh-add -L
100provides any output, and if so those keys are used. Note that this results in
101the comment on the key being the filename that was given to
102.Xr ssh-add 1
103when the key was loaded into your
104.Xr ssh-agent 1
105rather than the comment contained in that file, which is a bit of a shame.
106Otherwise, if
107.Xr ssh-add 1
108provides no keys contents of the
109.Ic default_ID_file
110will be used.
111.Pp
112The
113.Ic default_ID_file
114is the most recent file that matches:
115.Pa ~/.ssh/id*.pub ,
116(excluding those that match
117.Pa ~/.ssh/*-cert.pub )
118so if you create a key that is not the one you want
119.Nm
120to use, just use
121.Xr touch 1
122on your preferred key's
123.Pa .pub
124file to reinstate it as the most recent.
125.Pp
126.Sh EXAMPLES
127If you have already installed keys from one system on a lot of remote
128hosts, and you then create a new key, on a new client machine, say,
129it can be difficult to keep track of which systems on which you've
130installed the new key. One way of dealing with this is to load both
131the new key and old key(s) into your
132.Xr ssh-agent 1 .
133Load the new key first, without the
134.Fl c
135option, then load one or more old keys into the agent, possibly by
136ssh-ing to the client machine that has that old key, using the
137.Fl A
138option to allow agent forwarding:
139.Pp
140.D1 user@newclient$ ssh-add
141.D1 user@newclient$ ssh -A old.client
142.D1 user@oldl$ ssh-add -c
143.D1 No ... prompt for pass-phrase ...
144.D1 user@old$ logoff
145.D1 user@newclient$ ssh someserver
146.Pp
147now, if the new key is installed on the server, you'll be allowed in
148unprompted, whereas if you only have the old key(s) enabled, you'll be
149asked for confirmation, which is your cue to log back out and run
150.Pp
151.D1 user@newclient$ ssh-copy-id -i someserver
152.Pp
153The reason you might want to specify the -i option in this case is to
154ensure that the comment on the installed key is the one from the
155.Pa .pub
156file, rather than just the filename that was loaded into you agent.
157It also ensures that only the id you intended is installed, rather than
158all the keys that you have in your
159.Xr ssh-agent 1 .
160Of course, you can specify another id, or use the contents of the
161.Xr ssh-agent 1
162as you prefer.
163.Pp
164Having mentioned
165.Xr ssh-add 1 Ns 's
166.Fl c
167option, you might consider using this whenever using agent forwarding
168to avoid your key being hijacked, but it is much better to instead use
169.Xr ssh 1 Ns 's
170.Ar ProxyCommand
171and
172.Fl W
173option,
174to bounce through remote servers while always doing direct end-to-end
175authentication. This way the middle hop(s) don't get access to your
176.Xr ssh-agent 1 .
177A web search for
178.Ql ssh proxycommand nc
179should prove enlightening (N.B. the modern approach is to use the
180.Fl W
181option, rather than
182.Xr nc 1 ) .
183.Sh "SEE ALSO"
184.Xr ssh 1 ,
185.Xr ssh-agent 1 ,
186.Xr sshd 8