SSHD(8) MAINTENANCE COMMANDS SSHD(8)
NAME
sshd - OpenSSH SSH daemon
SYNOPSIS
sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c
host_certificate_file] [-E log_file] [-f config_file] [-g
login_grace_time] [-h host_key_file] [-k key_gen_time] [-o
option] [-p port] [-u len]
DESCRIPTION
sshd (OpenSSH Daemon) is the daemon program for ssh(1).
Together these programs replace rlogin and rsh, and provide
secure encrypted communications between two untrusted hosts
over an insecure network.
sshd listens for connections from clients. It is normally
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.
sshd can be configured using command-line options or a con-
figuration file (by default sshd_config(5)) ; command-line
options override values specified in the configuration file.
sshd rereads its configuration file when it receives a
hangup signal, SIGHUP, by executing itself with the name and
options it was started with, e.g. /usr/sbin/sshd.
The options are as follows:
-4 Forces sshd to use IPv4 addresses only.
-6 Forces sshd to use IPv6 addresses only.
-b bits
Specifies the number of bits in the ephemeral protocol
version 1 server key (default 1024).
-C connection_spec
Specify the connection parameters to use for the -T
extended test mode. If provided, any Match directives
in the configuration file that would apply to the
specified user, host, and address will be set before
the configuration is written to standard output. The
connection parameters are supplied as keyword=value
pairs. The keywords are ``user'', ``host'', ``laddr'',
``lport'', and ``addr''. All are required and may be
supplied in any order, either with multiple -C options
or as a comma-separated list.
-c host_certificate_file
Specifies a path to a certificate file to identify sshd
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during key exchange. The certificate file must match a
host key file specified using the -h option or the
HostKey configuration directive.
-D When this option is specified, sshd will not detach and
does not become a daemon. This allows easy monitoring
of sshd.
-d Debug mode. The server sends verbose debug output to
standard error, 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. Multiple -d options
increase the debugging level. Maximum is 3.
-E log_file
Append debug logs to log_file instead of the system
log.
-e Write debug logs to standard error instead of the sys-
tem log.
-f config_file
Specifies the name of the configuration file. The
default is /etc/ssh/sshd_config. sshd refuses to start
if there is no configuration file.
-g login_grace_time
Gives the grace time for clients to authenticate them-
selves (default 120 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 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 any-
one but root). The default is /etc/ssh/ssh_host_key
for protocol version 1, and /etc/ssh/ssh_host_dsa_key,
/etc/ssh/ssh_host_ecdsa_key.
/etc/ssh/ssh_host_ed25519_key and
/etc/ssh/ssh_host_rsa_key for protocol version 2. It
is possible to have multiple host key files for the
different protocol versions and host key algorithms.
-i Specifies that sshd is being run from inetd(8). If SSH
protocol 1 is enabled, sshd should not normally be run
from inetd because it needs to generate the server key
before it can respond to the client, and this may take
some time. Clients may have to wait too long if the
key was regenerated every time.
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-k key_gen_time
Specifies how often the ephemeral protocol version 1
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 regen-
erated.
-o option
Can be used to give options in the format used in the
configuration file. This is useful for specifying
options for which there is no separate command-line
flag. For full details of the options, and their
values, see sshd_config(5).
-p port
Specifies the port on which the server listens for con-
nections (default 22). Multiple port options are per-
mitted. Ports specified in the configuration file with
the Port option are ignored when a command-line port is
specified. Ports specified using the ListenAddress
option override command-line ports.
-q Quiet mode. Nothing is sent to the system log. Nor-
mally the beginning, authentication, and termination of
each connection is logged.
-T Extended test mode. Check the validity of the confi-
guration file, output the effective configuration to
stdout and then exit. Optionally, Match rules may be
applied by specifying the connection parameters using
one or more -C options.
-t Test mode. Only check the validity of the configura-
tion 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 overflow this field to
still be uniquely identified. Specifying -u0 indicates
that only dotted decimal addresses should be put into
the utmp file. -u0 may also be used to prevent sshd
from making DNS requests unless the authentication
mechanism or configuration requires it. Authentication
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mechanisms that may require DNS include RhostsRSAAu-
thentication, HostbasedAuthentication, and using a
from="pattern-list" option in a key file. Configura-
tion options that require DNS include using a USER@HOST
pattern in AllowUsers or DenyUsers.
AUTHENTICATION
The OpenSSH SSH daemon supports SSH protocols 1 and 2. The
default is to use protocol 2 only, though this can be
changed via the Protocol option in sshd_config(5). Protocol
1 should not be used and is only offered to support legacy
devices.
Each host has a host-specific key, used to identify the
host. Partial forward security for protocol 1 is provided
through an additional server key, normally 1024 bits, gen-
erated when the server starts. This key is normally regen-
erated 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 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 use this random number as a
session key which is used to encrypt all further communica-
tions in the session. The rest of the session 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.
For protocol 2, 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 AES. The
client selects the encryption algorithm to use from those
offered by the server. Additionally, session integrity is
provided through a cryptographic message authentication code
(hmac-md5, hmac-sha1, umac-64, umac-128, hmac-ripemd160,
hmac-sha2-256 or hmac-sha2-512).
Finally, the server and the client enter an authentication
dialog. The client tries to authenticate itself using
host-based authentication, public key authentication,
challenge-response authentication, or password authentica-
tion.
Regardless of the authentication type, the account is
checked to ensure that it is accessible. An account is not
accessible if it is locked, listed in DenyUsers or its group
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is listed in DenyGroups . The definition of a locked
account is system dependant. Some platforms have their own
account database (eg AIX) and some modify the passwd field (
`*LK*' on Solaris and UnixWare, `*' on HP-UX, containing
`Nologin' on Tru64, a leading `*LOCKED*' on FreeBSD and a
leading `!' on most Linuxes). If there is a requirement to
disable password authentication for the account while allow-
ing still public-key, then the passwd field should be set to
something other than these values (eg `NP' or `*NP*' ).
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 connections, or for-
warding the authentication agent connection over the secure
channel.
After this, 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.
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 ~/.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 the file ~/.ssh/environment, if it exists, and
users are allowed to change their environment. See the
PermitUserEnvironment option in sshd_config(5).
7. Changes to user's home directory.
8. If ~/.ssh/rc exists and the sshd_config(5) PermitUserRC
option is set, runs it; else if /etc/ssh/sshrc exists,
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runs it; otherwise runs xauth. The ``rc'' files are
given the X11 authentication protocol and cookie in
standard input. See SSHRC , below.
9. Runs user's shell or command. All commands are run
under the user's login shell as specified in the system
password database.
SSHRC
If the file ~/.ssh/rc exists, sh(1) runs it after reading
the environment files but before starting the user's shell
or command. It must not produce any output on stdout;
stderr must be used instead. If X11 forwarding is in use,
it will receive the "proto cookie" pair in its standard
input (and DISPLAY in its environment). The script must
call xauth(1) because sshd will not run xauth automatically
to add X11 cookies.
The primary purpose of this file is to run any initializa-
tion 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 && [ -n "$DISPLAY" ]; then
if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ];
then
# X11UseLocalhost=yes
echo add unix:`echo $DISPLAY |
cut -c11-` $proto $cookie
else
# X11UseLocalhost=no
echo add $DISPLAY $proto $cookie
fi | 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 add the cookie.
AUTHORIZED_KEYS FILE FORMAT
AuthorizedKeysFile specifies the files containing public
keys for public key authentication; if this option is not
specified, the default is ~/.ssh/authorized_keys and
~/.ssh/authorized_keys2. Each line of the file contains one
key (empty lines and lines starting with a `#' are ignored
as comments). Protocol 1 public keys consist of the follow-
ing space-separated fields: options, bits, exponent,
modulus, comment. Protocol 2 public key consist of:
options, keytype, base64-encoded key, comment. The options
field is optional; its presence is determined by whether the
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line starts with a number or not (the options field never
starts with a number). The bits, exponent, modulus, and
comment fields give the RSA key for protocol version 1; the
comment field is not used for anything (but may be con-
venient for the user to identify the key). For protocol
version 2 the keytype is ``ecdsa-sha2-nistp256'', ``ecdsa-
sha2-nistp384'', ``ecdsa-sha2-nistp521'', ``ssh-ed25519'',
``ssh-dss'' or ``ssh-rsa''.
Note that lines in this file are usually several hundred
bytes long (because of the size of the public key encoding)
up to a limit of 8 kilobytes, which permits DSA keys up to 8
kilobits and RSA keys up to 16 kilobits. You don't want to
type them in; instead, copy the identity.pub, id_dsa.pub,
id_ecdsa.pub, id_ed25519.pub, or the id_rsa.pub file and
edit it.
sshd enforces a minimum RSA key modulus size for protocol 1
and protocol 2 keys of 768 bits.
The options (if present) consist of comma-separated option
specifications. No spaces are permitted, except within dou-
ble quotes. The following option specifications are sup-
ported (note that option keywords are case-insensitive):
agent-forwarding
Enable authentication agent forwarding previously dis-
abled by the restrict option.
cert-authority
Specifies that the listed key is a certification
authority (CA) that is trusted to validate signed cer-
tificates for user authentication.
Certificates may encode access restrictions similar to
these key options. If both certificate restrictions
and key options are present, the most restrictive union
of the two is applied.
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 client requests a pty; otherwise it is run
without a tty. If an 8-bit clean channel is required,
one must not request a pty or should specify no-pty. A
quote may be included in the command by quoting it with
a backslash. This option might be useful to restrict
certain public keys to perform just a specific opera-
tion. An example might be a key that permits remote
backups but nothing else. Note that the client may
specify TCP and/or X11 forwarding unless they are
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explicitly prohibited. The command originally supplied
by the client is available in the SSH_ORIGINAL_COMMAND
environment variable. Note that this option applies to
shell, command or subsystem execution. Also note that
this command may be superseded by either a
sshd_config(5) ForceCommand directive or a command
embedded in a certificate.
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. Environment processing is disabled by
default and is controlled via the PermitUserEnvironment
option. This option is automatically disabled if
UseLogin is enabled.
from="pattern-list"
Specifies that in addition to public key authentica-
tion, either the canonical name of the remote host or
its IP address must be present in the comma-separated
list of patterns. See PATTERNS in ssh_config(5) for
more information on patterns.
In addition to the wildcard matching that may be
applied to hostnames or addresses, a from stanza may
match IP addresses using CIDR address/masklen notation.
The purpose of this option is to optionally increase
security: public key 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).
no-agent-forwarding
Forbids authentication agent forwarding when this key
is used for authentication.
no-port-forwarding
Forbids TCP 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-pty
Prevents tty allocation (a request to allocate a pty
will fail).
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no-user-rc
Disables execution of ~/.ssh/rc.
no-X11-forwarding
Forbids X11 forwarding when this key is used for
authentication. Any X11 forward requests by the client
will return an error.
permitopen="host:port"
Limit local port forwarding with ssh(1) -L such that it
may only connect to the specified host and port. IPv6
addresses can be specified by enclosing the address in
square brackets. 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. A port specification of
* matches any port.
port-forwarding
Enable port forwarding previously disabled by the res-
trict
principals="principals"
On a cert-authority line, specifies allowed principals
for certificate authentication as a comma-separated
list. At least one name from the list must appear in
the certificate's list of principals for the certifi-
cate to be accepted. This option is ignored for keys
that are not marked as trusted certificate signers
using the cert-authority option.
pty Permits tty allocation previously disabled by the res-
trict option.
restrict
Enable all restrictions, i.e. disable port, agent and
X11 forwarding, as well as disabling PTY allocation and
execution of ~/.ssh/rc. If any future restriction
capabilities are added to authorized_keys files they
will be included in this set.
tunnel="n"
Force a tun(4) device on the server. Without this
option, the next available device will be used if the
client requests a tunnel.
user-rc
Enables execution of ~/.ssh/rc previously disabled by
the restrict option.
X11-forwarding
Permits X11 forwarding previously disabled by the
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restrict option.
An example authorized_keys file:
# Comments allowed at start of line
ssh-rsa AAAAB3Nza...LiPk== user@example.net
from="*.sales.example.net,!pc.sales.example.net" ssh-
rsa
AAAAB2...19Q== john@example.net
command="dump /home",no-pty,no-port-forwarding ssh-dss
AAAAC3...51R== example.net
permitopen="192.0.2.1:80",permitopen="192.0.2.2:25"
ssh-dss
AAAAB5...21S==
tunnel="0",command="sh /etc/netstart tun0" ssh-rsa
AAAA...==
jane@example.net
restrict,command="uptime" ssh-rsa AAAA1C8...32Tv==
user@example.net
restrict,pty,command="nethack" ssh-rsa
AAAA1f8...IrrC5==
user@example.net
SSH_KNOWN_HOSTS FILE FORMAT
The /etc/ssh/ssh_known_hosts and ~/.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 added to the
per-user file.
Each line in these files contains the following fields:
markers (optional), hostnames, bits, exponent, modulus, com-
ment. The fields are separated by spaces.
The marker is optional, but if it is present then it must be
one of ``@cert-authority'', to indicate that the line con-
tains a certification authority (CA) key, or ``@revoked'',
to indicate that the key contained on the line is revoked
and must not ever be accepted. Only one marker should be
used on a key line.
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. A hostname or address may optionally be
enclosed within `[' and `]' brackets then followed by `:'
and a non-standard port number.
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Alternately, hostnames may be stored in a hashed form which
hides host names and addresses should the file's contents be
disclosed. Hashed hostnames start with a `|' character.
Only one hashed hostname may appear on a single line and
none of the above negation or wildcard operators may be
applied.
Bits, exponent, and modulus are taken directly from the RSA
host key; they can be obtained, for example, from
/etc/ssh/ssh_host_key.pub. The optional comment field con-
tinues 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; either one
that matches exactly or, if the server has presented a cer-
tificate for authentication, the key of the certification
authority that signed the certificate. For a key to be
trusted as a certification authority, it must use the
``@cert-authority'' marker described above.
The known hosts file also provides a facility to mark keys
as revoked, for example when it is known that the associated
private key has been stolen. Revoked keys are specified by
including the ``@revoked'' marker at the beginning of the
key line, and are never accepted for authentication or as
certification authorities, but instead will produce a warn-
ing from ssh(1) when they are encountered.
It is permissible (but not recommended) to have several
lines or different host keys for the same names. This will
inevitably happen when short forms of host names from dif-
ferent 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,
ssh-keyscan(1) or by taking /etc/ssh/ssh_host_key.pub and
adding the host names at the front. ssh-keygen(1) also
offers some basic automated editing for ~/.ssh/known_hosts
including removing hosts matching a host name and converting
all host names to their hashed representations.
An example ssh_known_hosts file:
# Comments allowed at start of line
closenet,...,192.0.2.53 1024 37 159...93
closenet.example.net
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cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
# A hashed hostname
|1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM=
ssh-rsa
AAAA1234.....=
# A revoked key
@revoked * ssh-rsa AAAAB5W...
# A CA key, accepted for any host in *.mydomain.com or
*.mydomain.org
@cert-authority *.mydomain.org,*.mydomain.com ssh-rsa
AAAAB5W...
FILES
~/.hushlogin
This file is used to suppress printing the last login
time and /etc/motd, if PrintLastLog and PrintMotd,
respectively, are enabled. It does not suppress print-
ing of the banner specified by Banner.
~/.rhosts
This file is used for host-based authentication (see
ssh(1) for more information). On some machines this
file may need to be world-readable if the user's home
directory is on an NFS partition, because sshd reads it
as root. Additionally, this file must be owned by the
user, and must not have write permissions for anyone
else. The recommended permission for most machines is
read/write for the user, and not accessible by others.
~/.shosts
This file is used in exactly the same way as .rhosts,
but allows host-based authentication without permitting
login with rlogin/rsh.
~/.ssh/
This directory is the default location for all user-
specific configuration and authentication information.
There is no general requirement to keep the entire con-
tents of this directory secret, but the recommended
permissions are read/write/execute for the user, and
not accessible by others.
~/.ssh/authorized_keys
Lists the public keys (DSA, ECDSA, Ed25519, RSA) that
can be used for logging in as this user. The format of
this file is described above. The content of the file
is not highly sensitive, but the recommended permis-
sions are read/write for the user, and not accessible
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by others.
If this file, the ~/.ssh directory, or the user's home
directory are writable by other users, then the file
could be modified or replaced by unauthorized users.
In this case, sshd will not allow it to be used unless
the StrictModes option has been set to ``no''.
~/.ssh/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. The file should be writable only
by the user; it need not be readable by anyone else.
Environment processing is disabled by default and is
controlled via the PermitUserEnvironment option.
~/.ssh/known_hosts
Contains a list of host keys for all hosts the user has
logged into that are not already in the systemwide list
of known host keys. The format of this file is
described above. This file should be writable only by
root/the owner and can, but need not be, world-
readable.
~/.ssh/rc
Contains initialization routines to be run before the
user's home directory becomes accessible. This file
should be writable only by the user, and need not be
readable by anyone else.
/etc/hosts.allow
/etc/hosts.deny
Access controls that should be enforced by tcp-wrappers
are defined here. Further details described in
hosts_access(5).
/etc/hosts.equiv
This file is for host-based authentication (see ssh(1))
. It should only be writable by root.
/etc/ssh/moduli
Contains Diffie-Hellman groups used for the "Diffie-
Hellman Group Exchange" key exchange method. The file
format is described in moduli(5). If no usable groups
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are found in this file then fixed internal groups will
be used.
/etc/motd
See motd(5).
/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/ssh/shosts.equiv
This file is used in exactly the same way as
hosts.equiv, but allows host-based authentication
without permitting login with rlogin/rsh.
/etc/ssh/ssh_host_key
/etc/ssh/ssh_host_dsa_key
/etc/ssh/ssh_host_ecdsa_key
/etc/ssh/ssh_host_ed25519_key
/etc/ssh/ssh_host_rsa_key
These 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 these files are group/world-
accessible.
/etc/ssh/ssh_host_key.pub
/etc/ssh/ssh_host_dsa_key.pub
/etc/ssh/ssh_host_ecdsa_key.pub
/etc/ssh/ssh_host_ed25519_key.pub
/etc/ssh/ssh_host_rsa_key.pub
These 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
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files. These files are created using ssh-keygen(1).
/etc/ssh/ssh_known_hosts
Systemwide list of known host keys. This file should
be prepared by the system administrator to contain the
public host keys of all machines in the organization.
The format of this file is described above. This file
should be writable only by root/the owner and should be
world-readable.
/etc/ssh/sshd_config
Contains configuration data for sshd. The file format
and configuration options are described in
sshd_config(5).
/etc/ssh/sshrc
Similar to ~/.ssh/rc, it can be used to specify
machine-specific login-time initializations globally.
This file should be writable only by root, and should
be world-readable.
/var/empty
chroot(2) directory used by sshd during privilege
separation in the pre-authentication phase. The direc-
tory should not contain any files and must be owned by
root and not group or world-writable.
/etc/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 pro-
cess ID of the one started last). The content of this
file is not sensitive; it can be world-readable.
SEE ALSO
scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-
keygen(1), ssh-keyscan(1), chroot(2), hosts_access(5),
login.conf(5), moduli(5), sshd_config(5), inetd(8), sftp-
server(8)
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 created OpenSSH.
Markus Friedl contributed the support for SSH protocol ver-
sions 1.5 and 2.0. Niels Provos and Markus Friedl
Last change: February 17 2016 15
SSHD(8) MAINTENANCE COMMANDS SSHD(8)
contributed support for privilege separation.
Last change: February 17 2016 16
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