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NAME
sshd - secure shell daemon
SYNOPSIS
sshd [-b bits] [-d ] [-f config_file] [-g login_grace_time]
[-h host_key_file] [-i ] [-k key_gen_time] [-p port] [-q ]
[-V version]
DESCRIPTION
Sshd (Secure Shell Daemon) is the daemon program for ssh.
Together these programs replace rlogin and rsh programs, 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 normally started at boot from /etc/rc.local
or equivalent. It forks a new daemon for each incoming con-
nection. The forked daemons handle key exchange, encryp-
tion, authentication, command execution, and data exchange.
Sshd works as follows. Each host has a host-specific RSA
key (normally 1024 bits) used to identify the host. Addi-
tionally, 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, the daemon sends its
host and server public keys to the client. The client com-
pares the host key against its own database 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 start to 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,
IDEA, DES, 3DES, ARCFOUR, and TSS (a fast home-grown algo-
rithm) are supported. IDEA is 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 dia-
log. The client tries to authenticate itself using .rhosts
authentication, .rhosts authentication combined with RSA
host authentication, RSA challenge-response authentication,
TIS channenge 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), rexecd(8), and rexd (8)
are disabled (thus completely disabling rlogin(1) and rsh(1)
into that machine).
If the client successfully authenticates itself, a dialog
for preparing the session is entered. At this time the
client may request things like allocating a pseudo-tty, for-
warding X11 connections, forwarding TCP/IP 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 connections 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 con-
figuration file. Command-line options override values
specified in the configuration file.
Sshd rereads its configuration file if signal, SIGHUP.
OPTIONS
-b bits
Specifies the number of bits in the server key (default
768).
-d Debug mode. The server sends verbose debug output to
the system log, and does not put itself in the back-
ground. The server also will not fork and will only
process one connection. This option is only intended
for debugging for the server.
-f configuration_file
Specifies the name of the configuration file. The
default is /etc/sshd_config.
-g login_grace_time
Gives the grace time for clients to authenticate them-
selves (default 600 seconds). If the client fails to
authenticate the user within this many seconds, the
server disconnects and exits. A value of zero indi-
cates no limit.
-h host_key_file
Specifies the file from which the host key is read
(default /etc/ssh_host_key). This option must be given
if sshd is not run as root (as the normal host file is
normally not readable by anyone but root).
-i Specifies that sshd is being run from inetd. Sshd is
normally not run from inetd because it needs to gen-
erate the server key before it can respond to the
client, and this may take tens of seconds. Clients
would have to wait too long if the key was regenerated
every time. However, with small key sizes (e.g. 512)
using sshd from inetd may be feasible.
-k key_gen_time
Specifies how often the server key is regenerated
(default 3600 seconds, or one hour). The motivation
for regenerating the key fairly often is that the key
is not 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.
-p port
Specifies the port on which the server listens for con-
nections (default 22).
-q Quiet mode. Nothing is sent to the system log. Nor-
mally the beginning, authentication, and termination of
each connection is logged.
-V SSH version 2 compatibility mode. Server assumes that
SSH version 2 daemon has already read the version
number string from the client and this option gives the
version string read from the client.
CONFIGURATION FILE
Sshd reads configuration data from /etc/sshd_config (or the
file specified with -f on the command line). The file con-
tains keyword-value pairs, one per line. Lines starting
with '#' and empty lines are interpreted as comments.
The following keywords are possible. Keywords are case
insensitive.
AllowGroups
This keyword can be followed by any number of group
name patterns, separated by spaces. If specified, login
is allowed only if users primary group name matches one
of the patterns. '*' and '?' can be used as wildcards
in the patterns. By default, logins as all users are
allowed.
Note that the all other login authentication steps must
still be sucessfully completed. AllowGroups and Deny-
Groups are additional restrictions.
AllowHosts
This keyword can be followed by any number of host name
patterns, separated by spaces. If specified, login is
allowed only from hosts whose name matches one of the
patterns. '*' and '?' can be used as wildcards in the
patterns. Normal name servers are used to map the
client's host into a canonical host name. If the name
cannot be mapped, its IP-address is used as the host
name. By default all hosts are allowed to connect.
Note that sshd can also be configured to use
tcp_wrappers using the --with-libwrap compile-time con-
figuration option.
AccountExpireWarningDays
Specifies when to start print warning messages that the
account is going to expire. The value is number of days
before the account expiration. The default value is 14
days, and if set to 0 the warning messages are dis-
abled.
AllowSHosts
This keyword can be followed by any number of host name
patterns, separated by spaces. If specified, .shosts
(and .rhosts and /etc/hosts.equiv) entries are only
honoured for hosts whose name matches one of the pat-
terns. servers are used to map the client's host into
a canonical host name. If the name cannot be mapped,
its IP-address is used as the host name. By default
all hosts are allowed to connect.
AllowTcpForwarding
Specifies whether tcp forwarding is permitted. The
default is "yes". Note that disabling tcp forwarding
does not improve security in any way, as users can
always install their own forwarders.
AllowUsers
This keyword can be followed by any number of user name
patterns or user@host patterns, separated by spaces.
Host name may be either the dns name or the ip address.
If specified, login is allowed only as users whose name
matches one of the patterns. '*' and '?' can be used as
wildcards in the patterns. By default, logins as all
users are allowed.
Note that the all other login authentication steps must
still be sucessfully completed. AllowUsers and Den-
yUsers are additional restrictions.
CheckMail
Specifies whether sshd should print information whether
you have new mail or not when a user logs in interac-
tively. (On some systems it is also printed by the
shell, /etc/profile, or equivalent.) The default is
"yes".
DenyGroups
This keyword can be followed by any number of group
name patterns, separated by spaces. If specified, login
is disallowed if users primary group name name matches
any of the patterns.
DenyHosts
This keyword can be followed by any number of host name
patterns, separated by spaces. If specified, login is
disallowed from the hosts whose name matches any of the
patterns.
DenySHosts
This keyword can be followed by any number of host name
patterns, separated by spaces. If specified, .shosts
(and .rhosts and /etc/hosts.equiv) entries whose name
matches any of the patterns are ignored.
DenyUsers
This keyword can be followed by any number of user name
patterns or user@host patterns, separated by spaces.
Host name may be either the dns name or the ip address.
If specified, login is disallowed as users whose name
matches any of the patterns.
FascistLogging
Specifies whether to use verbose logging. Verbose log-
ging violates the privacy of users and is not recom-
mended. The argument must be "yes" or "no" (without
the quotes). The default is "no".
ForcedEmptyPasswdChange
Specifies whether to force password change if the pass-
word is empty (first login). . The argument must be
"yes" or "no" (without the quotes). The default is
"no".
ForcedPasswdChange
Specifies whether to force password change if the pass-
word is expired. The argument must be "yes" or "no"
(without the quotes). The default is "yes".
HostKey
Specifies the file containing the private host key
(default /etc/ssh_host_key).
IdleTimeout time
Sets idle timeout limit to time in seconds (s or noth-
ing after number), in minutes (m), in hours (h), in
days (d), or in weeks (w). If the connection have been
idle (all channels) for that long time the child pro-
cess is killed with SIGHUP, and connection is closed
down.
IgnoreRhosts
Specifies that rhosts and shosts files will not be used
in authentication. /etc/hosts.equiv and
/etc/shosts.equiv are still used. The default is "no".
IgnoreRootRhosts
Specifies that rhosts and shosts files will not be used
in authentication for root. The default is the value
of IgnoreRhosts.
KeepAlive
Specifies whether the system should send keepalive mes-
sages to the other side. If they are sent, death of
the connection or crash of one of the machines will be
properly noticed. However, this means that connections
will die if the route is down temporarily, and some
people find it annoying. On the other hand, if
keepalives are not send, 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 reboots. This avoids infinitely hanging
sessions.
To disable keepalives, the value should be set to "no"
in both the server and the client configuration files.
KerberosAuthentication
Specifies whether Kerberos V5 authentication is
allowed. This can be in the form of a Kerberos ticket,
or if PasswordAuthentication is yes, the password pro-
vided by the user will be validated through the Ker-
beros KDC or DCE Security Server. Default is yes.
KerberosOrLocalPasswd
If set then if password authentication through Kerberos
fails then the password will be validated via any addi-
tional local mechanism such as /etc/passwd or SecurID.
Default is no.
KerberosTgtPassing
Specifies whether a Kerberos V5 TGT may be forwarded to
the server. Default is yes.
KeyRegenerationInterval
The server key is automatically regenerated after this
many seconds (if it has been used). The purpose of
regeneration is to prevent decrypting captured sessions
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 ip address of the interface where the
sshd server socket is bind.
LoginGraceTime
The server disconnects after this time if the user has
not successfully logged in. If the value is 0, there
is no time limit. The default is 600 (seconds).
PasswordAuthentication
Specifies whether password authentication is allowed.
The default is "yes".
PasswordExpireWarningDays
Specifies when to start print warning messages that the
password is going to expire. The value is number of
days before the password expiration. The default value
is 14 days, and if set to 0 the warning messages are
disabled.
PermitEmptyPasswords
When password authentication is allowed, it specifies
whether the server allows login to accounts with empty
password strings. The default is "yes".
PermitRootLogin
Specifies whether the root can log in using ssh. May
be set to "yes", "nopwd", or "no". The default is
"yes", allowing root logins through any of the authen-
tication types allowed for other users. The "nopwd"
value disables password-authenticated root logins. The
"no" value disables root logins through any of the
authentication methods. ("nopwd" and "no" are
equivalent unless you have a .rhosts, .shosts, or
.ssh/authorized_keys file in the root home directory.)
Root login with RSA authentication when the "command"
option has been specified will be allowed regardless of
the value of this setting (which may be useful for tak-
ing remote backups even if root login is normally not
allowed).
PidFile
Specifies the location of the file containing the pro-
cess ID of the master sshd daemon (default:
/etc/sshd.pid or /var/run/sshd.pid, depending on the
system).
Port Specifies the port number that sshd listens on. The
default is 22.
PrintMotd
Specifies whether sshd should print /etc/motd when a
user logs in interactively. (On some systems it is
also printed by the shell, /etc/profile, or
equivalent.) The default is "yes".
QuietMode
Specifies whether the system runs in quiet mode. In
quiet mode, nothing is logged in the system log, except
fatal errors. The default is "no".
RandomSeed
Specifies the file containing the random seed for the
server; this file is created automatically and updated
regularly. The default is /etc/ssh_random_seed.
RhostsAuthentication
Specifies whether authentication using rhosts or
/etc/hosts.equiv files is sufficient. Normally, this
method should not be permitted 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".
RhostsRSAAuthentication
Specifies whether rhosts or /etc/hosts.equiv authenti-
cation together with successful RSA host authentication
is allowed. The default is "yes".
RSAAuthentication
Specifies whether pure RSA authentication is allowed.
The default is "yes".
ServerKeyBits
Defines the number of bits in the server key. The
minimum value is 512, and the default is 768.
SilentDeny
Specifies wheter denied (or not allowed) connections
are denied silently (just close the connection, no log-
ging etc) or are they closed cleanly (send error mes-
sage and log connection attempt).
StrictModes
Specifies whether ssh should check file modes and own-
ership of the user's home directory and rhosts files
before accepting login. This is normally desirable
because novices sometimes accidentally leave their
directory or files world-writable. The default is
"yes".
SyslogFacility
Gives the facility code that is used when logging mes-
sages from sshd. The possible values are: DAEMON, USER,
AUTH, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5,
LOCAL6, LOCAL7. The default is DAEMON.
TISAuthentication
Specifies wether authentication through TIS authsrv (8)
is allowed. The default is "no".
Umask
Sets default umask for sshd and its childs. Remember to
add 0 in front of the number to make it octal. Default
is to not set umask at all.
X11Forwarding
Specifies whether X11 forwarding is permitted. The
default is "yes". Note that disabling X11 forwarding
does not improve security in any way, as users can
always install their own forwarders.
X11DisplayOffset
Specifies the first display number available for sshd's
X11 forwarding. This prevents sshd from interfering
with real X11 servers.
XAuthLocation
Specifies the default path to xauth program.
LOGIN PROCESS
When a user successfully logs in, sshd does the following:
1. If the login is on a tty, and no command has been
specified, prints last login time and /etc/motd (unless
prevented in the configuration file or by
$HOME/.hushlogin; see the FILES section).
2. If the login is on a tty, records login time.
3. Checks /etc/nologin; if it exists, prints contents and
quits (unless root).
4. Changes to run with normal user privileges.
5. Sets up basic environment.
6. Reads /etc/environment if it exists.
7. Reads $HOME/.ssh/environment if it exists.
8. Changes to user's home directory.
9. If $HOME/.ssh/rc exists, runs it (with the user's
shell); else if /etc/sshrc exists, runs it (with
/bin/sh); otherwise runs xauth. The "rc" files are
given the X11 authentication protocol and cookie in
standard input.
10. Runs user's shell or command.
AUTHORIZED_KEYS FILE FORMAT
The $HOME/.ssh/authorized_keys file lists the RSA keys that
are permitted for RSA authentication. Each line of the file
contains one key (empty lines and lines starting with a '#'
are ignored as comments). Each line consists of the follow-
ing fields, separated by spaces: options, bits, exponent,
modulus, comment. The options field is optional; its pres-
ence is determined by whether the line starts with a number
or not (the option field never starts with a number). The
bits, exponent, modulus and comment fields give the RSA key;
the comment field is not used for anything (but may be con-
venient for the user to identify the key).
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 file and edit it.
The options (if present) consists of comma-separated option
specifications. No spaces are permitted, except within dou-
ble quotes. Option names are case insensitive. The follow-
ing option specifications are supported:
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 or name servers or anything (but
the key); however, if somebody somehow steals the key,
the key permits an intruder to log in from anywhere in
the world. This additional option makes using a stolen
key more difficult (name servers and/or routers would
have to be compromised in addition to just the key).
command="command"
Specifies that the command is executed whenever this
key is used for authentication. The command supplied
by the user (if any) is ignored. The command is run on
a pty if the connection requests a pty; otherwise it is
run without a tty. A quote may be included in the com-
mand by quoting it with a backslash. This option might
be useful to restrict certain RSA keys to perform just
a specific operation. An example might be a key that
permits remote backups but nothing else. Notice that
the client may specify TCP/IP and/or X11 forwardings
unless they are explicitly prohibited.
environment="NAME=value"
Specifies that the string is to be added to the
environment when logging in using this key. Environ-
ment variables set this way override other default
environment values. Multiple options of this type are
permitted.
idle-timeout=time
Sets idle timeout limit to time in seconds (s or noth-
ing after number), in minutes (m), in hours (h), in
days (d), or in weeks (w). If the connection have been
idle (all channels) for that long time the child pro-
cess is killed with SIGHUP, and connection is closed
down.
no-port-forwarding
Forbids TCP/IP forwarding when this key is used for
authentication. 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).
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
SSH WITH TCP WRAPPERS
When sshd is compiled with tcp wrappers libraries, then the
host.allow/deny files also controls who can connect to ports
forwarded by sshd.
The program names in the hosts.allow/deny files are
sshdfwd-<portname>, sshdfwd-<portnumber>, and sshdfwd-X11
for forwarded ports the ssh client or server is listening.
If the port has name defined then you must use it.
SSH_KNOWN_HOSTS FILE FORMAT
The /etc/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 admistrator (optional), and
the per-user file is maintained automatically: whenever the
user connects an unknown host its key is added to the per-
user file. The recommended way to create
/etc/ssh_known_hosts is to use the make-ssh-known-hosts com-
mand.
Each line in these files contains the following fields:
hostnames, bits, exponent, modulus, comment. The fields are
separated by spaces.
Hostnames is a comma-separated list of patterns ('*' and '?'
act as wildcards); each pattern in turn is matched against
the canonical host name (when authenticating a client) or
against the user-supplied name (when authenticating a
server). A pattern may also be preceded by '!' to indicate
negation: if the host name matches a negated pattern, it is
not accepted (by that line) even if it matched another pat-
tern on the line.
Bits, exponent, and modulus are taken directly from the host
key; they can be obtained e.g. from /etc/ssh_host_key.pub.
The optional comment field continues to the end of the line,
and is not used.
Lines starting with '#' and empty lines are ignored as com-
ments.
When performing host authentication, authentication is
accepted if any matching line has the proper key. It is
thus permissible (but not recommended) to have several lines
or different host keys for the same names. This will inev-
itably happen when short forms of host names from different
domains are put in the file. It is possible that the files
contain conflicting 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
(see make-ssh-known-hosts(1)) or by taking
/etc/ssh_host_key.pub and adding the host names at the
front.
Examples
closenet,closenet.hut.fi,...,130.233.208.41 1024 37 159...93
closenet.hut.fi
FILES
/etc/sshd_config
Contains configuration data for sshd. This file should
be writable by root only, but it is recommended (though
not necessary) that it be world-readable.
/etc/ssh_host_key
Contains the private part of the host key. This file
is normally created automatically by "make install",
but can also be created manually using ssh-keygen(1).
This file should only be owned by root, readable only
by root, and not accessible to others.
/etc/ssh_host_key.pub
Contains the public part of the host key. This file is
normally created automatically by "make install", but
can also be created manually. This file should be
world-readable but writable only by root. Its contents
should match the private part. This file is not really
used for anything; it is only provided for the conveni-
ence of the user so its contents can be copied to known
hosts files.
/etc/ssh_random_seed
This file contains a seed for the random number genera-
tor. This file should only be accessible by root.
/var/run/sshd.pid
Contains the process id of the sshd listening for con-
nections (if there are several daemons running con-
currently for different ports, this contains the pid of
the one started last). The contents of this file are
not sensitive; it can be world-readable.
$HOME/.ssh/authorized_keys
Lists the RSA keys that can be used to log into the
user's account. This file must be readable by root
(which may on some machines imply it being world-
readable if the user's home directory resides on an NFS
volume). It is recommended that it not be accessible
by others. The format of this file is described above.
/etc/ssh_known_hosts and $HOME/.ssh/known_hosts
These files are consulted when using rhosts with RSA
host authentication to check 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 the remote host is the one we intended to con-
nect.) These files should be writable only by root/the
owner. /etc/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.
$HOME/.rhosts
This file contains host-username pairs, separated by a
space, one per line. The given user on the correspond-
ing host is permitted to log in without password. The
same file is used by rlogind and rshd. Ssh differs
from rlogind and rshd in that it requires RSA host
authentication in addition to validating the host name
retrieved from domain name servers (unless compiled
with the --with-rhosts configuration option). The file
must be writable only by the user; it is recommended
that it not be accessible by others.
It 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 fol-
lowed by a user name; such users are permitted to log
in as any user on this machine (except root). Addi-
tionally, 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. Addition-
ally, 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 accounts that own critical
binaries and directories. Using a user name practi-
cally grants the user root access. The only valid use
for user names that I can think of is in negative
entries. Note that this warning also applies to
rsh/rlogin.
/etc/shosts.equiv
This is processed exactly as /etc/hosts.equiv. However,
this file may be useful in environments that want to
run both rsh/rlogin and ssh.
/etc/environment
This file is read into the environment at login (if it
exists). It can only contain empty lines, comment
lines (that start with '#'), and assignment lines of
the form name=value. This file is processed in all
environments (normal rsh/rlogin only process it on AIX
and potentially some other systems). The file should
be writable only by root, and should be world-readable.
$HOME/.ssh/environment
This file is read into the environment after
/etc/environment. It has the same format. 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 the user's shell
after reading the environment files but before starting
the user's shell or command. If X11 spoofing is in
use, this will receive the "proto cookie" pair in stan-
dard input (and DISPLAY in environment). This must
call xauth in that case.
The primary purpose of this file is to run any initial-
ization routines which may be needed before the user's
home directory becomes accessible; AFS is a particular
example of such an environment.
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/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/sshrc
Like $HOME/.ssh/rc, but run with /bin/sh. This can be
used to specify machine-specific login-time initializa-
tions globally. This file should be writable only by
root, and should be world-readable.
/etc/sshd_tis.map
Establishes a mapping between a local username and its
corresponding name in the TIS database. Each line con-
tains the local name followed by a ":" followed by the
corresponding name. If the file does not exist or the
user is not found, the corresponding name in the TIS
database is supposed to be the same.
INSTALLATION
Sshd is normally run as root. If it is not run as root, it
can only log in as the user it is running as, and password
authentication may not work if the system uses shadow pass-
words. An alternative host key file must also be used.
Sshd is normally started from /etc/rc.local or equivalent at
system boot.
Considerable work has been put to making sshd secure. How-
ever, if you find a security problem, please report it
immediately to <ssh-bugs@cs.hut.fi>.
AUTHOR
Tatu Ylonen <ylo@ssh.fi>
Information about new releases, mailing lists, and other
related issues can be found from the ssh WWW home page at
http://www.cs.hut.fi/ssh.
SEE ALSO
ssh(1), make-ssh-known-hosts(1), ssh-keygen(1), ssh-
agent(1), ssh-add(1), scp(1), rlogin(1), rsh(1)
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