[-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]
DESCRIPTION
sshd (SSH Daemon) is the daemon program for ssh(1). Together these pro-
grams replace rlogin and rsh, and provide secure encrypted communications
between two untrusted hosts over an insecure network. The programs are
intended to be as easy to install and use as possible.
sshd is the daemon that listens for connections from clients. It is nor-
mally started at boot from /etc/rc. It forks a new daemon for each
incoming connection. The forked daemons handle key exchange, encryption,
authentication, command execution, and data exchange. This implementa-
tion of sshd supports both SSH protocol version 1 and 2 simultaneously.
sshd works as follows.
SSH protocol version 1
Each host has a host-specific RSA key (normally 1024 bits) used to iden-
tify the host. Additionally, when the daemon starts, it generates a
server RSA key (normally 768 bits). This key is normally regenerated
every hour if it has been used, and is never stored on disk.
Whenever a client connects the daemon responds with its public host and
server keys. The client compares the RSA host key against its own data-
base to verify that it has not changed. The client then generates a 256
bit random number. It encrypts this random number using both the host
key and the server key, and sends the encrypted number to the server.
Both sides then use this random number as a session key which is used to
encrypt all further communications in the session. The rest of the ses-
sion is encrypted using a conventional cipher, currently Blowfish or
3DES, with 3DES being used by default. The client selects the encryption
algorithm to use from those offered by the server.
Next, the server and the client enter an authentication dialog. The
client tries to authenticate itself using .rhosts authentication, .rhosts
authentication combined with RSA host authentication, RSA challenge-
response authentication, or password based authentication.
Rhosts authentication is normally disabled because it is fundamentally
insecure, but can be enabled in the server configuration file if desired.
System security is not improved unless rshd(8), rlogind(8), and rexecd(8)
are disabled (thus completely disabling rlogin(1) and rsh(1) into the
machine).
SSH protocol version 2
Version 2 works similarly: Each host has a host-specific key (RSA or DSA)
used to identify the host. However, when the daemon starts, it does not
generate a server key. Forward security is provided through a Diffie-
Hellman key agreement. This key agreement results in a shared session
key.
The rest of the session is encrypted using a symmetric cipher, currently
128 bit AES, Blowfish, 3DES, CAST128, Arcfour, 192 bit AES, or 256 bit
connections, or forwarding the authentication agent connection over the
secure channel.
Finally, the client either requests a shell or execution of a command.
The sides then enter session mode. In this mode, either side may send
data at any time, and such data is forwarded to/from the shell or command
on the server side, and the user terminal in the client side.
When the user program terminates and all forwarded X11 and other connec-
tions have been closed, the server sends command exit status to the
client, and both sides exit.
sshd can be configured using command-line options or a configuration
file. Command-line options override values specified in the configura-
tion file.
sshd rereads its configuration file when it receives a hangup signal,
SIGHUP, by executing itself with the name it was started as, i.e.,
/usr/sbin/sshd.
The options are as follows:
-b bits
Specifies the number of bits in the ephemeral protocol version 1
server key (default 768).
-d Debug mode. The server sends verbose debug output to the system
log, and does not put itself in the background. The server also
will not fork and will only process one connection. This option
is only intended for debugging for the server. Multiple -d
options increase the debugging level. Maximum is 3.
-e When this option is specified, sshd will send the output to the
standard error instead of the system log.
-f configuration_file
Specifies the name of the configuration file. The default is
/etc/ssh/sshd_config. sshd refuses to start if there is no con-
figuration file.
-g login_grace_time
Gives the grace time for clients to authenticate themselves
(default 600 seconds). If the client fails to authenticate the
user within this many seconds, the server disconnects and exits.
A value of zero indicates no limit.
-h host_key_file
Specifies a file from which a host key is read. This option must
be given if sshd is not run as root (as the normal host key files
are normally not readable by anyone but root). The default is
/etc/ssh/ssh_host_key for protocol version 1, and
/etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_dsa_key for pro-
stored anywhere, and after about an hour, it becomes impossible
to recover the key for decrypting intercepted communications even
if the machine is cracked into or physically seized. A value of
zero indicates that the key will never be regenerated.
-o option
Can be used to give options in the format used in the configura-
tion file. This is useful for specifying options for which there
is no separate command-line flag.
-p port
Specifies the port on which the server listens for connections
(default 22). Multiple port options are permitted. Ports speci-
fied in the configuration file are ignored when a command-line
port is specified.
-q Quiet mode. Nothing is sent to the system log. Normally the
beginning, authentication, and termination of each connection is
logged.
-t Test mode. Only check the validity of the configuration file and
sanity of the keys. This is useful for updating sshd reliably as
configuration options may change.
-u len This option is used to specify the size of the field in the utmp
structure that holds the remote host name. If the resolved host
name is longer than len, the dotted decimal value will be used
instead. This allows hosts with very long host names that over-
flow this field to still be uniquely identified. Specifying -u0
indicates that only dotted decimal addresses should be put into
the utmp file. -u0 is also be used to prevent sshd from making
DNS requests unless the authentication mechanism or configuration
requires it. Authentication mechanisms that may require DNS
include RhostsAuthentication, RhostsRSAAuthentication,
HostbasedAuthentication and using a from="pattern-list" option in
a key file. Configuration options that require DNS include using
a USER@HOST pattern in AllowUsers or DenyUsers.
-D When this option is specified sshd will not detach and does not
become a daemon. This allows easy monitoring of sshd.
-4 Forces sshd to use IPv4 addresses only.
-6 Forces sshd to use IPv6 addresses only.
CONFIGURATION FILE
sshd reads configuration data from /etc/ssh/sshd_config (or the file
specified with -f on the command line). The file contains keyword-argu-
ment pairs, one per line. Lines starting with `#' and empty lines are
interpreted as comments.
The possible keywords and their meanings are as follows (note that key-
AllowTcpForwarding
Specifies whether TCP forwarding is permitted. The default is
``yes''. Note that disabling TCP forwarding does not improve
security unless users are also denied shell access, as they can
always install their own forwarders.
AllowUsers
This keyword can be followed by a list of user name patterns,
separated by spaces. If specified, login is allowed only for
users names that match one of the patterns. `*' and `'? can be
used as wildcards in the patterns. Only user names are valid; a
numerical user ID is not recognized. By default, login is
allowed for all users. If the pattern takes the form USER@HOST
then USER and HOST are separately checked, restricting logins to
particular users from particular hosts.
AuthorizedKeysFile
Specifies the file that contains the public keys that can be used
for user authentication. AuthorizedKeysFile may contain tokens
of the form %T which are substituted during connection set-up.
The following tokens are defined: %% is replaced by a literal
'%', %h is replaced by the home directory of the user being
authenticated and %u is replaced by the username of that user.
After expansion, AuthorizedKeysFile is taken to be an absolute
path or one relative to the user's home directory. The default
is ``.ssh/authorized_keys''.
Banner In some jurisdictions, sending a warning message before authenti-
cation may be relevant for getting legal protection. The con-
tents of the specified file are sent to the remote user before
authentication is allowed. This option is only available for
protocol version 2.
ChallengeResponseAuthentication
Specifies whether challenge response authentication is allowed.
All authentication styles from login.conf(5) are supported. The
default is ``yes''.
Ciphers
Specifies the ciphers allowed for protocol version 2. Multiple
ciphers must be comma-separated. The default is
``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
aes192-cbc,aes256-cbc''
ClientAliveInterval
Sets a timeout interval in seconds after which if no data has
been received from the client, sshd will send a message through
the encrypted channel to request a response from the client. The
default is 0, indicating that these messages will not be sent to
the client. This option applies to protocol version 2 only.
15, and ClientAliveCountMax is left at the default, unresponsive
ssh clients will be disconnected after approximately 45 seconds.
DenyGroups
This keyword can be followed by a list of group name patterns,
separated by spaces. Login is disallowed for users whose primary
group or supplementary group list matches one of the patterns.
`*' and `'? can be used as wildcards in the patterns. Only
group names are valid; a numerical group ID is not recognized.
By default, login is allowed for all groups.
DenyUsers
This keyword can be followed by a list of user name patterns,
separated by spaces. Login is disallowed for user names that
match one of the patterns. `*' and `'? can be used as wildcards
in the patterns. Only user names are valid; a numerical user ID
is not recognized. By default, login is allowed for all users.
If the pattern takes the form USER@HOST then USER and HOST are
separately checked, restricting logins to particular users from
particular hosts.
GatewayPorts
Specifies whether remote hosts are allowed to connect to ports
forwarded for the client. By default, sshd binds remote port
forwardings to the loopback addresss. This prevents other remote
hosts from connecting to forwarded ports. GatewayPorts can be
used to specify that sshd should bind remote port forwardings to
the wildcard address, thus allowing remote hosts to connect to
forwarded ports. The argument must be ``yes'' or ``no''. The
default is ``no''.
HostbasedAuthentication
Specifies whether rhosts or /etc/hosts.equiv authentication
together with successful public key client host authentication is
allowed (hostbased authentication). This option is similar to
RhostsRSAAuthentication and applies to protocol version 2 only.
The default is ``no''.
HostKey
Specifies a file containing a private host key used by SSH. The
default is /etc/ssh/ssh_host_key for protocol version 1, and
/etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_dsa_key for pro-
tocol version 2. Note that sshd will refuse to use a file if it
is group/world-accessible. It is possible to have multiple host
key files. ``rsa1'' keys are used for version 1 and ``dsa'' or
``rsa'' are used for version 2 of the SSH protocol.
IgnoreRhosts
Specifies that .rhosts and .shosts files will not be used in
RhostsAuthentication, RhostsRSAAuthentication or
HostbasedAuthentication.
keepalives are not sent, sessions may hang indefinitely on the
server, leaving ``ghost'' users and consuming server resources.
The default is ``yes'' (to send keepalives), and the server will
notice if the network goes down or the client host crashes. This
avoids infinitely hanging sessions.
To disable keepalives, the value should be set to ``no''.
KerberosAuthentication
Specifies whether Kerberos authentication is allowed. This can
be in the form of a Kerberos ticket, or if PasswordAuthentication
is yes, the password provided by the user will be validated
through the Kerberos KDC. To use this option, the server needs a
Kerberos servtab which allows the verification of the KDC's iden-
tity. Default is ``yes''.
KerberosOrLocalPasswd
If set then if password authentication through Kerberos fails
then the password will be validated via any additional local
mechanism such as /etc/passwd. Default is ``yes''.
KerberosTgtPassing
Specifies whether a Kerberos TGT may be forwarded to the server.
Default is ``no'', as this only works when the Kerberos KDC is
actually an AFS kaserver.
KerberosTicketCleanup
Specifies whether to automatically destroy the user's ticket
cache file on logout. Default is ``yes''.
KeyRegenerationInterval
In protocol version 1, the ephemeral server key is automatically
regenerated after this many seconds (if it has been used). The
purpose of regeneration is to prevent decrypting captured ses-
sions by later breaking into the machine and stealing the keys.
The key is never stored anywhere. If the value is 0, the key is
never regenerated. The default is 3600 (seconds).
ListenAddress
Specifies the local addresses sshd should listen on. The follow-
ing forms may be used:
ListenAddress host|IPv4_addr|IPv6_addr
ListenAddress host|IPv4_addr:port
ListenAddress [host|IPv6_addr]:port
If port is not specified, sshd will listen on the address and all
prior Port options specified. The default is to listen on all
local addresses. Multiple ListenAddress options are permitted.
Additionally, any Port options must precede this option for non
port qualified addresses.
MACs Specifies the available MAC (message authentication code) algo-
rithms. The MAC algorithm is used in protocol version 2 for data
integrity protection. Multiple algorithms must be comma-sepa-
rated. The default is
``hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96''.
MaxStartups
Specifies the maximum number of concurrent unauthenticated con-
nections to the sshd daemon. Additional connections will be
dropped until authentication succeeds or the LoginGraceTime
expires for a connection. The default is 10.
Alternatively, random early drop can be enabled by specifying the
three colon separated values ``start:rate:full'' (e.g.,
"10:30:60"). sshd will refuse connection attempts with a proba-
bility of ``rate/100'' (30%) if there are currently ``start''
(10) unauthenticated connections. The probability increases lin-
early and all connection attempts are refused if the number of
unauthenticated connections reaches ``full'' (60).
PAMAuthenticationViaKbdInt
Specifies whether PAM challenge response authentication is
allowed. This allows the use of most PAM challenge response
authentication modules, but it will allow password authentication
regardless of whether PasswordAuthentication is disabled. The
default is ``no''.
PasswordAuthentication
Specifies whether password authentication is allowed. The
default is ``yes''.
PermitEmptyPasswords
When password authentication is allowed, it specifies whether the
server allows login to accounts with empty password strings. The
default is ``no''.
PermitRootLogin
Specifies whether root can login using ssh(1). The argument must
be ``yes'', ``without-password'', ``forced-commands-only'' or
``no''. The default is ``yes''.
If this option is set to ``without-password'' password authenti-
cation is disabled for root.
If this option is set to ``forced-commands-only'' root login with
public key authentication will be allowed, but only if the
command option has been specified (which may be useful for taking
remote backups even if root login is normally not allowed). All
other authentication methods are disabled for root.
If this option is set to ``no'' root is not allowed to login.
interactively. (On some systems it is also printed by the shell,
/etc/profile, or equivalent.) The default is ``yes''.
Protocol
Specifies the protocol versions sshd should support. The possi-
ble values are ``1'' and ``2''. Multiple versions must be comma-
separated. The default is ``2,1''.
PubkeyAuthentication
Specifies whether public key authentication is allowed. The
default is ``yes''. Note that this option applies to protocol
version 2 only.
RhostsAuthentication
Specifies whether authentication using rhosts or /etc/hosts.equiv
files is sufficient. Normally, this method should not be permit-
ted because it is insecure. RhostsRSAAuthentication should be
used instead, because it performs RSA-based host authentication
in addition to normal rhosts or /etc/hosts.equiv authentication.
The default is ``no''. This option applies to protocol version 1
only.
RhostsRSAAuthentication
Specifies whether rhosts or /etc/hosts.equiv authentication
together with successful RSA host authentication is allowed. The
default is ``no''. This option applies to protocol version 1
only.
RSAAuthentication
Specifies whether pure RSA authentication is allowed. The
default is ``yes''. This option applies to protocol version 1
only.
ServerKeyBits
Defines the number of bits in the ephemeral protocol version 1
server key. The minimum value is 512, and the default is 768.
StrictModes
Specifies whether sshd should check file modes and ownership of
the user's files and home directory before accepting login. This
is normally desirable because novices sometimes accidentally
leave their directory or files world-writable. The default is
``yes''.
Subsystem
Configures an external subsystem (e.g., file transfer daemon).
Arguments should be a subsystem name and a command to execute
upon subsystem request. The command sftp-server(8) implements
the ``sftp'' file transfer subsystem. By default no subsystems
are defined. Note that this option applies to protocol version 2
only.
Specifies whether sshd should try to verify the remote host name
and check that the resolved host name for the remote IP address
maps back to the very same IP address. The default is ``no''.
X11DisplayOffset
Specifies the first display number available for sshd's X11 for-
warding. This prevents sshd from interfering with real X11
servers. The default is 10.
X11Forwarding
Specifies whether X11 forwarding is permitted. The default is
``no''. Note that disabling X11 forwarding does not improve
security in any way, as users can always install their own for-
warders. X11 forwarding is automatically disabled if UseLogin is
enabled.
X11UseLocalhost
Specifies whether sshd should bind the X11 forwarding server to
the loopback address or to the wildcard address. By default,
sshd binds the forwarding server to the loopback address and sets
the hostname part of the DISPLAY environment variable to
``localhost''. This prevents remote hosts from connecting to the
fake display. However, some older X11 clients may not function
with this configuration. X11UseLocalhost may be set to ``no'' to
specify that the forwarding server should be bound to the wild-
card address. The argument must be ``yes'' or ``no''. The
default is ``yes''.
XAuthLocation
Specifies the location of the xauth(1) program. The default is
/usr/X11R6/bin/xauth.
Time Formats
sshd command-line arguments and configuration file options that specify
time may be expressed using a sequence of the form: time[qualifier],
where time is a positive integer value and qualifier is one of the fol-
lowing:
<none> seconds
s | S seconds
m | M minutes
h | H hours
d | D days
w | W weeks
Each member of the sequence is added together to calculate the total time
value.
Time format examples:
600 600 seconds (10 minutes)
10m 10 minutes
4. Changes to run with normal user privileges.
5. Sets up basic environment.
6. Reads $HOME/.ssh/environment if it exists.
7. Changes to user's home directory.
8. If $HOME/.ssh/rc exists, runs it; else if /etc/ssh/sshrc
exists, runs it; otherwise runs xauth. The ``rc'' files are
given the X11 authentication protocol and cookie in standard
input.
9. Runs user's shell or command.
AUTHORIZED_KEYS FILE FORMAT
$HOME/.ssh/authorized_keys is the default file that lists the public keys
that are permitted for RSA authentication in protocol version 1 and for
public key authentication (PubkeyAuthentication) in protocol version 2.
AuthorizedKeysFile may be used to specify an alternative file.
Each line of the file contains one key (empty lines and lines starting
with a `#' are ignored as comments). Each RSA public key consists of the
following fields, separated by spaces: options, bits, exponent, modulus,
comment. Each protocol version 2 public key consists of: options, key-
type, base64 encoded key, comment. The options fields are optional; its
presence is determined by whether the line starts with a number or not
(the option field never starts with a number). The bits, exponent, modu-
lus and comment fields give the RSA key for protocol version 1; the com-
ment field is not used for anything (but may be convenient for the user
to identify the key). For protocol version 2 the keytype is ``ssh-dss''
or ``ssh-rsa''.
Note that lines in this file are usually several hundred bytes long
(because of the size of the RSA key modulus). You don't want to type
them in; instead, copy the identity.pub, id_dsa.pub or the id_rsa.pub
file and edit it.
The options (if present) consist of comma-separated option specifica-
tions. No spaces are permitted, except within double quotes. The fol-
lowing option specifications are supported (note that option keywords are
case-insensitive):
from="pattern-list"
Specifies that in addition to RSA authentication, the canonical
name of the remote host must be present in the comma-separated
list of patterns (`*' and `'? serve as wildcards). The list may
also contain patterns negated by prefixing them with `'!; if the
canonical host name matches a negated pattern, the key is not
accepted. The purpose of this option is to optionally increase
security: RSA authentication by itself does not trust the network
to perform just a specific operation. An example might be a key
that permits remote backups but nothing else. Note that the
client may specify TCP/IP and/or X11 forwarding unless they are
explicitly prohibited. Note that this option applies to shell,
command or subsystem execution.
environment="NAME=value"
Specifies that the string is to be added to the environment when
logging in using this key. Environment variables set this way
override other default environment values. Multiple options of
this type are permitted. This option is automatically disabled
if UseLogin is enabled.
no-port-forwarding
Forbids TCP/IP forwarding when this key is used for authentica-
tion. Any port forward requests by the client will return an
error. This might be used, e.g., in connection with the command
option.
no-X11-forwarding
Forbids X11 forwarding when this key is used for authentication.
Any X11 forward requests by the client will return an error.
no-agent-forwarding
Forbids authentication agent forwarding when this key is used for
authentication.
no-pty Prevents tty allocation (a request to allocate a pty will fail).
permitopen="host:port"
Limit local ``ssh -L'' port forwarding such that it may only con-
nect to the specified host and port. IPv6 addresses can be spec-
ified with an alternative syntax: host/port. Multiple permitopen
options may be applied separated by commas. No pattern matching
is performed on the specified hostnames, they must be literal
domains or addresses.
Examples
1024 33 12121...312314325 ylo@foo.bar
from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23...2334 ylo@niksula
command="dump /home",no-pty,no-port-forwarding 1024 33 23...2323
backup.hut.fi
permitopen="10.2.1.55:80",permitopen="10.2.1.56:25" 1024 33 23...2323
SSH_KNOWN_HOSTS FILE FORMAT
The /etc/ssh/ssh_known_hosts, and $HOME/.ssh/known_hosts files contain
host public keys for all known hosts. The global file should be prepared
by the administrator (optional), and the per-user file is maintained
automatically: whenever the user connects from an unknown host its key is
comment field continues to the end of the line, and is not used.
Lines starting with `#' and empty lines are ignored as comments.
When performing host authentication, authentication is accepted if any
matching line has the proper key. It is thus permissible (but not recom-
mended) to have several lines or different host keys for the same names.
This will inevitably happen when short forms of host names from different
domains are put in the file. It is possible that the files contain con-
flicting information; authentication is accepted if valid information can
be found from either file.
Note that the lines in these files are typically hundreds of characters
long, and you definitely don't want to type in the host keys by hand.
Rather, generate them by a script or by taking /etc/ssh/ssh_host_key.pub
and adding the host names at the front.
Examples
closenet,...,130.233.208.41 1024 37 159...93 closenet.hut.fi
cvs.openbsd.org,199.185.137.3 ssh-rsa AAAA1234.....=
FILES
/etc/ssh/sshd_config
Contains configuration data for sshd. This file should be
writable by root only, but it is recommended (though not neces-
sary) that it be world-readable.
/etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key,
/etc/ssh/ssh_host_rsa_key
These three files contain the private parts of the host keys.
These files should only be owned by root, readable only by root,
and not accessible to others. Note that sshd does not start if
this file is group/world-accessible.
/etc/ssh/ssh_host_key.pub, /etc/ssh/ssh_host_dsa_key.pub,
/etc/ssh/ssh_host_rsa_key.pub
These three files contain the public parts of the host keys.
These files should be world-readable but writable only by root.
Their contents should match the respective private parts. These
files are not really used for anything; they are provided for the
convenience of the user so their contents can be copied to known
hosts files. These files are created using ssh-keygen(1).
/etc/moduli
Contains Diffie-Hellman groups used for the "Diffie-Hellman Group
Exchange".
/var/run/sshd.pid
Contains the process ID of the sshd listening for connections (if
there are several daemons running concurrently for different
ports, this contains the pid of the one started last). The con-
tent of this file is not sensitive; it can be world-readable.
the public key of the host. The key must be listed in one of
these files to be accepted. The client uses the same files to
verify that it is connecting to the correct remote host. These
files should be writable only by root/the owner.
/etc/ssh/ssh_known_hosts should be world-readable, and
$HOME/.ssh/known_hosts can but need not be world-readable.
/etc/nologin
If this file exists, sshd refuses to let anyone except root log
in. The contents of the file are displayed to anyone trying to
log in, and non-root connections are refused. The file should be
world-readable.
/etc/hosts.allow, /etc/hosts.deny
Access controls that should be enforced by tcp-wrappers are
defined here. Further details are described in hosts_access(5).
$HOME/.rhosts
This file contains host-username pairs, separated by a space, one
per line. The given user on the corresponding host is permitted
to log in without password. The same file is used by rlogind and
rshd. The file must be writable only by the user; it is recom-
mended that it not be accessible by others.
If is also possible to use netgroups in the file. Either host or
user name may be of the form +@groupname to specify all hosts or
all users in the group.
$HOME/.shosts
For ssh, this file is exactly the same as for .rhosts. However,
this file is not used by rlogin and rshd, so using this permits
access using SSH only.
/etc/hosts.equiv
This file is used during .rhosts authentication. In the simplest
form, this file contains host names, one per line. Users on
those hosts are permitted to log in without a password, provided
they have the same user name on both machines. The host name may
also be followed by a user name; such users are permitted to log
in as any user on this machine (except root). Additionally, the
syntax ``+@group'' can be used to specify netgroups. Negated
entries start with `-'.
If the client host/user is successfully matched in this file,
login is automatically permitted provided the client and server
user names are the same. Additionally, successful RSA host
authentication is normally required. This file must be writable
only by root; it is recommended that it be world-readable.
Warning: It is almost never a good idea to use user names in
hosts.equiv. Beware that it really means that the named user(s)
can log in as anybody, which includes bin, daemon, adm, and other
It can only contain empty lines, comment lines (that start with
`#'), and assignment lines of the form name=value. The file
should be writable only by the user; it need not be readable by
anyone else.
$HOME/.ssh/rc
If this file exists, it is run with /bin/sh after reading the
environment files but before starting the user's shell or com-
mand. If X11 spoofing is in use, this will receive the "proto
cookie" pair in standard input (and DISPLAY in environment).
This must call xauth(1) in that case.
The primary purpose of this file is to run any initialization
routines which may be needed before the user's home directory
becomes accessible; AFS is a particular example of such an envi-
ronment.
This file will probably contain some initialization code followed
by something similar to:
if read proto cookie; then
echo add $DISPLAY $proto $cookie | xauth -q -
fi
If this file does not exist, /etc/ssh/sshrc is run, and if that
does not exist either, xauth is used to store the cookie.
This file should be writable only by the user, and need not be
readable by anyone else.
/etc/ssh/sshrc
Like $HOME/.ssh/rc. This can be used to specify machine-specific
login-time initializations globally. This file should be
writable only by root, and should be world-readable.
AUTHORS
OpenSSH is a derivative of the original and free ssh 1.2.12 release by
Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
de Raadt and Dug Song removed many bugs, re-added newer features and cre-
ated OpenSSH. Markus Friedl contributed the support for SSH protocol
versions 1.5 and 2.0.
SEE ALSO
scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1),
login.conf(5), moduli(5), sftp-server(8)
T. Ylonen, T. Kivinen, M. Saarinen, T. Rinne, and S. Lehtinen, SSH
Protocol Architecture, draft-ietf-secsh-architecture-09.txt, July 2001,
work in progress material.
M. Friedl, N. Provos, and W. A. Simpson, Diffie-Hellman Group Exchange
for the SSH Transport Layer Protocol, draft-ietf-secsh-dh-group-
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