| .\" -*- nroff -*- |
| .\" |
| .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
| .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| .\" All rights reserved |
| .\" |
| .\" As far as I am concerned, the code I have written for this software |
| .\" can be used freely for any purpose. Any derived versions of this |
| .\" software must be clearly marked as such, and if the derived work is |
| .\" incompatible with the protocol description in the RFC file, it must be |
| .\" called by a name other than "ssh" or "Secure Shell". |
| .\" |
| .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. |
| .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. |
| .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. |
| .\" |
| .\" Redistribution and use in source and binary forms, with or without |
| .\" modification, are permitted provided that the following conditions |
| .\" are met: |
| .\" 1. Redistributions of source code must retain the above copyright |
| .\" notice, this list of conditions and the following disclaimer. |
| .\" 2. Redistributions in binary form must reproduce the above copyright |
| .\" notice, this list of conditions and the following disclaimer in the |
| .\" documentation and/or other materials provided with the distribution. |
| .\" |
| .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| .\" |
| .\" $OpenBSD: sshd_config.5,v 1.21 2003/07/22 13:35:22 markus Exp $ |
| .Dd September 25, 1999 |
| .Dt SSHD_CONFIG 5 |
| .Os |
| .Sh NAME |
| .Nm sshd_config |
| .Nd OpenSSH SSH daemon configuration file |
| .Sh SYNOPSIS |
| .Bl -tag -width Ds -compact |
| .It Pa /etc/ssh/sshd_config |
| .El |
| .Sh DESCRIPTION |
| .Nm sshd |
| reads configuration data from |
| .Pa /etc/ssh/sshd_config |
| (or the file specified with |
| .Fl f |
| on the command line). |
| The file contains keyword-argument pairs, one per line. |
| Lines starting with |
| .Ql # |
| and empty lines are interpreted as comments. |
| .Pp |
| The possible |
| keywords and their meanings are as follows (note that |
| keywords are case-insensitive and arguments are case-sensitive): |
| .Bl -tag -width Ds |
| .It Cm AllowGroups |
| This keyword can be followed by a list of group name patterns, separated |
| by spaces. |
| If specified, login is allowed only for users whose primary |
| group or supplementary group list matches one of the patterns. |
| .Ql \&* |
| and |
| .Ql \&? |
| 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. |
| .Pp |
| .It Cm AllowTcpForwarding |
| Specifies whether TCP forwarding is permitted. |
| The default is |
| .Dq 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. |
| .Pp |
| .It Cm AllowUsers |
| This keyword can be followed by a list of user name patterns, separated |
| by spaces. |
| If specified, login is allowed only for user names that |
| match one of the patterns. |
| .Ql \&* |
| and |
| .Ql \&? |
| 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. |
| .Pp |
| .It Cm AuthorizedKeysFile |
| Specifies the file that contains the public keys that can be used |
| for user authentication. |
| .Cm 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, |
| .Cm AuthorizedKeysFile |
| is taken to be an absolute path or one relative to the user's home |
| directory. |
| The default is |
| .Dq .ssh/authorized_keys . |
| .It Cm Banner |
| In some jurisdictions, sending a warning message before authentication |
| may be relevant for getting legal protection. |
| The contents of the specified file are sent to the remote user before |
| authentication is allowed. |
| This option is only available for protocol version 2. |
| By default, no banner is displayed. |
| .Pp |
| .It Cm ChallengeResponseAuthentication |
| Specifies whether challenge response authentication is allowed. |
| All authentication styles from |
| .Xr login.conf 5 |
| are supported. |
| The default is |
| .Dq yes . |
| .It Cm Ciphers |
| Specifies the ciphers allowed for protocol version 2. |
| Multiple ciphers must be comma-separated. |
| The default is |
| .Pp |
| .Bd -literal |
| ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour, |
| aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr'' |
| .Ed |
| .It Cm ClientAliveInterval |
| Sets a timeout interval in seconds after which if no data has been received |
| from the client, |
| .Nm 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. |
| .It Cm ClientAliveCountMax |
| Sets the number of client alive messages (see above) which may be |
| sent without |
| .Nm sshd |
| receiving any messages back from the client. |
| If this threshold is reached while client alive messages are being sent, |
| .Nm sshd |
| will disconnect the client, terminating the session. |
| It is important to note that the use of client alive messages is very |
| different from |
| .Cm KeepAlive |
| (below). |
| The client alive messages are sent through the encrypted channel |
| and therefore will not be spoofable. |
| The TCP keepalive option enabled by |
| .Cm KeepAlive |
| is spoofable. |
| The client alive mechanism is valuable when the client or |
| server depend on knowing when a connection has become inactive. |
| .Pp |
| The default value is 3. |
| If |
| .Cm ClientAliveInterval |
| (above) is set to 15, and |
| .Cm ClientAliveCountMax |
| is left at the default, unresponsive ssh clients |
| will be disconnected after approximately 45 seconds. |
| .It Cm Compression |
| Specifies whether compression is allowed. |
| The argument must be |
| .Dq yes |
| or |
| .Dq no . |
| The default is |
| .Dq yes . |
| .It Cm 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. |
| .Ql \&* |
| and |
| .Ql \&? |
| 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. |
| .Pp |
| .It Cm 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. |
| .Ql \&* |
| and |
| .Ql \&? |
| 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. |
| .It Cm GatewayPorts |
| Specifies whether remote hosts are allowed to connect to ports |
| forwarded for the client. |
| By default, |
| .Nm sshd |
| binds remote port forwardings to the loopback address. |
| This prevents other remote hosts from connecting to forwarded ports. |
| .Cm GatewayPorts |
| can be used to specify that |
| .Nm sshd |
| should bind remote port forwardings to the wildcard address, |
| thus allowing remote hosts to connect to forwarded ports. |
| The argument must be |
| .Dq yes |
| or |
| .Dq no . |
| The default is |
| .Dq no . |
| .It Cm 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 |
| .Cm RhostsRSAAuthentication |
| and applies to protocol version 2 only. |
| The default is |
| .Dq no . |
| .It Cm HostKey |
| Specifies a file containing a private host key |
| used by SSH. |
| The default is |
| .Pa /etc/ssh/ssh_host_key |
| for protocol version 1, and |
| .Pa /etc/ssh/ssh_host_rsa_key |
| and |
| .Pa /etc/ssh/ssh_host_dsa_key |
| for protocol version 2. |
| Note that |
| .Nm sshd |
| will refuse to use a file if it is group/world-accessible. |
| It is possible to have multiple host key files. |
| .Dq rsa1 |
| keys are used for version 1 and |
| .Dq dsa |
| or |
| .Dq rsa |
| are used for version 2 of the SSH protocol. |
| .It Cm IgnoreRhosts |
| Specifies that |
| .Pa .rhosts |
| and |
| .Pa .shosts |
| files will not be used in |
| .Cm RhostsAuthentication , |
| .Cm RhostsRSAAuthentication |
| or |
| .Cm HostbasedAuthentication . |
| .Pp |
| .Pa /etc/hosts.equiv |
| and |
| .Pa /etc/shosts.equiv |
| are still used. |
| The default is |
| .Dq yes . |
| .It Cm IgnoreUserKnownHosts |
| Specifies whether |
| .Nm sshd |
| should ignore the user's |
| .Pa $HOME/.ssh/known_hosts |
| during |
| .Cm RhostsRSAAuthentication |
| or |
| .Cm HostbasedAuthentication . |
| The default is |
| .Dq no . |
| .It Cm KeepAlive |
| Specifies whether the system should send TCP keepalive messages 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 sent, |
| sessions may hang indefinitely on the server, leaving |
| .Dq ghost |
| users and consuming server resources. |
| .Pp |
| The default is |
| .Dq yes |
| (to send keepalives), and the server will notice |
| if the network goes down or the client host crashes. |
| This avoids infinitely hanging sessions. |
| .Pp |
| To disable keepalives, the value should be set to |
| .Dq no . |
| .It Cm KerberosAuthentication |
| Specifies whether Kerberos authentication is allowed. |
| This can be in the form of a Kerberos ticket, or if |
| .Cm 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 identity. |
| Default is |
| .Dq no . |
| .It Cm KerberosOrLocalPasswd |
| If set then if password authentication through Kerberos fails then |
| the password will be validated via any additional local mechanism |
| such as |
| .Pa /etc/passwd . |
| Default is |
| .Dq yes . |
| .It Cm KerberosTgtPassing |
| Specifies whether a Kerberos TGT may be forwarded to the server. |
| Default is |
| .Dq no . |
| .It Cm KerberosTicketCleanup |
| Specifies whether to automatically destroy the user's ticket cache |
| file on logout. |
| Default is |
| .Dq yes . |
| .It Cm 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 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). |
| .It Cm ListenAddress |
| Specifies the local addresses |
| .Nm sshd |
| should listen on. |
| The following forms may be used: |
| .Pp |
| .Bl -item -offset indent -compact |
| .It |
| .Cm ListenAddress |
| .Sm off |
| .Ar host No | Ar IPv4_addr No | Ar IPv6_addr |
| .Sm on |
| .It |
| .Cm ListenAddress |
| .Sm off |
| .Ar host No | Ar IPv4_addr No : Ar port |
| .Sm on |
| .It |
| .Cm ListenAddress |
| .Sm off |
| .Oo |
| .Ar host No | Ar IPv6_addr Oc : Ar port |
| .Sm on |
| .El |
| .Pp |
| If |
| .Ar port |
| is not specified, |
| .Nm sshd |
| will listen on the address and all prior |
| .Cm Port |
| options specified. |
| The default is to listen on all local addresses. |
| Multiple |
| .Cm ListenAddress |
| options are permitted. |
| Additionally, any |
| .Cm Port |
| options must precede this option for non port qualified addresses. |
| .It Cm 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 120 seconds. |
| .It Cm LogLevel |
| Gives the verbosity level that is used when logging messages from |
| .Nm sshd . |
| The possible values are: |
| QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3. |
| The default is INFO. |
| DEBUG and DEBUG1 are equivalent. |
| DEBUG2 and DEBUG3 each specify higher levels of debugging output. |
| Logging with a DEBUG level violates the privacy of users and is not recommended. |
| .It Cm MACs |
| Specifies the available MAC (message authentication code) algorithms. |
| The MAC algorithm is used in protocol version 2 |
| for data integrity protection. |
| Multiple algorithms must be comma-separated. |
| The default is |
| .Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 . |
| .It Cm MaxStartups |
| Specifies the maximum number of concurrent unauthenticated connections to the |
| .Nm sshd |
| daemon. |
| Additional connections will be dropped until authentication succeeds or the |
| .Cm LoginGraceTime |
| expires for a connection. |
| The default is 10. |
| .Pp |
| Alternatively, random early drop can be enabled by specifying |
| the three colon separated values |
| .Dq start:rate:full |
| (e.g., "10:30:60"). |
| .Nm sshd |
| will refuse connection attempts with a probability of |
| .Dq rate/100 |
| (30%) |
| if there are currently |
| .Dq start |
| (10) |
| unauthenticated connections. |
| The probability increases linearly and all connection attempts |
| are refused if the number of unauthenticated connections reaches |
| .Dq full |
| (60). |
| .It Cm PasswordAuthentication |
| Specifies whether password authentication is allowed. |
| The default is |
| .Dq yes . |
| .It Cm PermitEmptyPasswords |
| When password authentication is allowed, it specifies whether the |
| server allows login to accounts with empty password strings. |
| The default is |
| .Dq no . |
| .It Cm PermitRootLogin |
| Specifies whether root can login using |
| .Xr ssh 1 . |
| The argument must be |
| .Dq yes , |
| .Dq without-password , |
| .Dq forced-commands-only |
| or |
| .Dq no . |
| The default is |
| .Dq yes . |
| .Pp |
| If this option is set to |
| .Dq without-password |
| password authentication is disabled for root. |
| .Pp |
| If this option is set to |
| .Dq forced-commands-only |
| root login with public key authentication will be allowed, |
| but only if the |
| .Ar 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. |
| .Pp |
| If this option is set to |
| .Dq no |
| root is not allowed to login. |
| .It Cm PermitUserEnvironment |
| Specifies whether |
| .Pa ~/.ssh/environment |
| and |
| .Cm environment= |
| options in |
| .Pa ~/.ssh/authorized_keys |
| are processed by |
| .Nm sshd . |
| The default is |
| .Dq no . |
| Enabling environment processing may enable users to bypass access |
| restrictions in some configurations using mechanisms such as |
| .Ev LD_PRELOAD . |
| .It Cm PidFile |
| Specifies the file that contains the process ID of the |
| .Nm sshd |
| daemon. |
| The default is |
| .Pa /var/run/sshd.pid . |
| .It Cm Port |
| Specifies the port number that |
| .Nm sshd |
| listens on. |
| The default is 22. |
| Multiple options of this type are permitted. |
| See also |
| .Cm ListenAddress . |
| .It Cm PrintLastLog |
| Specifies whether |
| .Nm sshd |
| should print the date and time when the user last logged in. |
| The default is |
| .Dq yes . |
| .It Cm PrintMotd |
| Specifies whether |
| .Nm sshd |
| should print |
| .Pa /etc/motd |
| when a user logs in interactively. |
| (On some systems it is also printed by the shell, |
| .Pa /etc/profile , |
| or equivalent.) |
| The default is |
| .Dq yes . |
| .It Cm Protocol |
| Specifies the protocol versions |
| .Nm sshd |
| supports. |
| The possible values are |
| .Dq 1 |
| and |
| .Dq 2 . |
| Multiple versions must be comma-separated. |
| The default is |
| .Dq 2,1 . |
| Note that the order of the protocol list does not indicate preference, |
| because the client selects among multiple protocol versions offered |
| by the server. |
| Specifying |
| .Dq 2,1 |
| is identical to |
| .Dq 1,2 . |
| .It Cm PubkeyAuthentication |
| Specifies whether public key authentication is allowed. |
| The default is |
| .Dq yes . |
| Note that this option applies to protocol version 2 only. |
| .It Cm RhostsAuthentication |
| Specifies whether authentication using rhosts or /etc/hosts.equiv |
| files is sufficient. |
| Normally, this method should not be permitted because it is insecure. |
| .Cm 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 |
| .Dq no . |
| This option applies to protocol version 1 only. |
| .It Cm RhostsRSAAuthentication |
| Specifies whether rhosts or /etc/hosts.equiv authentication together |
| with successful RSA host authentication is allowed. |
| The default is |
| .Dq no . |
| This option applies to protocol version 1 only. |
| .It Cm RSAAuthentication |
| Specifies whether pure RSA authentication is allowed. |
| The default is |
| .Dq yes . |
| This option applies to protocol version 1 only. |
| .It Cm ServerKeyBits |
| Defines the number of bits in the ephemeral protocol version 1 server key. |
| The minimum value is 512, and the default is 768. |
| .It Cm StrictModes |
| Specifies whether |
| .Nm 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 |
| .Dq yes . |
| .It Cm 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 |
| .Xr sftp-server 8 |
| implements the |
| .Dq sftp |
| file transfer subsystem. |
| By default no subsystems are defined. |
| Note that this option applies to protocol version 2 only. |
| .It Cm SyslogFacility |
| Gives the facility code that is used when logging messages from |
| .Nm sshd . |
| The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, |
| LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. |
| The default is AUTH. |
| .It Cm UseDNS |
| Specifies whether |
| .Nm sshd |
| should lookup 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 |
| .Dq yes . |
| .It Cm UseLogin |
| Specifies whether |
| .Xr login 1 |
| is used for interactive login sessions. |
| The default is |
| .Dq no . |
| Note that |
| .Xr login 1 |
| is never used for remote command execution. |
| Note also, that if this is enabled, |
| .Cm X11Forwarding |
| will be disabled because |
| .Xr login 1 |
| does not know how to handle |
| .Xr xauth 1 |
| cookies. |
| If |
| .Cm UsePrivilegeSeparation |
| is specified, it will be disabled after authentication. |
| .It Cm UsePAM |
| Enables PAM authentication (via challenge-response) and session set up. |
| If you enable this, you should probably disable |
| .Cm PasswordAuthentication . |
| If you enable |
| .CM UsePAM |
| then you will not be able to run sshd as a non-root user. |
| .It Cm UsePrivilegeSeparation |
| Specifies whether |
| .Nm sshd |
| separates privileges by creating an unprivileged child process |
| to deal with incoming network traffic. |
| After successful authentication, another process will be created that has |
| the privilege of the authenticated user. |
| The goal of privilege separation is to prevent privilege |
| escalation by containing any corruption within the unprivileged processes. |
| The default is |
| .Dq yes . |
| .It Cm X11DisplayOffset |
| Specifies the first display number available for |
| .Nm sshd Ns 's |
| X11 forwarding. |
| This prevents |
| .Nm sshd |
| from interfering with real X11 servers. |
| The default is 10. |
| .It Cm X11Forwarding |
| Specifies whether X11 forwarding is permitted. |
| The argument must be |
| .Dq yes |
| or |
| .Dq no . |
| The default is |
| .Dq no . |
| .Pp |
| When X11 forwarding is enabled, there may be additional exposure to |
| the server and to client displays if the |
| .Nm sshd |
| proxy display is configured to listen on the wildcard address (see |
| .Cm X11UseLocalhost |
| below), however this is not the default. |
| Additionally, the authentication spoofing and authentication data |
| verification and substitution occur on the client side. |
| The security risk of using X11 forwarding is that the client's X11 |
| display server may be exposed to attack when the ssh client requests |
| forwarding (see the warnings for |
| .Cm ForwardX11 |
| in |
| .Xr ssh_config 5 ) . |
| A system administrator may have a stance in which they want to |
| protect clients that may expose themselves to attack by unwittingly |
| requesting X11 forwarding, which can warrant a |
| .Dq no |
| setting. |
| .Pp |
| Note that disabling X11 forwarding does not prevent users from |
| forwarding X11 traffic, as users can always install their own forwarders. |
| X11 forwarding is automatically disabled if |
| .Cm UseLogin |
| is enabled. |
| .It Cm X11UseLocalhost |
| Specifies whether |
| .Nm sshd |
| should bind the X11 forwarding server to the loopback address or to |
| the wildcard address. |
| By default, |
| .Nm sshd |
| binds the forwarding server to the loopback address and sets the |
| hostname part of the |
| .Ev DISPLAY |
| environment variable to |
| .Dq localhost . |
| This prevents remote hosts from connecting to the proxy display. |
| However, some older X11 clients may not function with this |
| configuration. |
| .Cm X11UseLocalhost |
| may be set to |
| .Dq no |
| to specify that the forwarding server should be bound to the wildcard |
| address. |
| The argument must be |
| .Dq yes |
| or |
| .Dq no . |
| The default is |
| .Dq yes . |
| .It Cm XAuthLocation |
| Specifies the full pathname of the |
| .Xr xauth 1 |
| program. |
| The default is |
| .Pa /usr/X11R6/bin/xauth . |
| .El |
| .Ss Time Formats |
| .Nm sshd |
| command-line arguments and configuration file options that specify time |
| may be expressed using a sequence of the form: |
| .Sm off |
| .Ar time Op Ar qualifier , |
| .Sm on |
| where |
| .Ar time |
| is a positive integer value and |
| .Ar qualifier |
| is one of the following: |
| .Pp |
| .Bl -tag -width Ds -compact -offset indent |
| .It Cm <none> |
| seconds |
| .It Cm s | Cm S |
| seconds |
| .It Cm m | Cm M |
| minutes |
| .It Cm h | Cm H |
| hours |
| .It Cm d | Cm D |
| days |
| .It Cm w | Cm W |
| weeks |
| .El |
| .Pp |
| Each member of the sequence is added together to calculate |
| the total time value. |
| .Pp |
| Time format examples: |
| .Pp |
| .Bl -tag -width Ds -compact -offset indent |
| .It 600 |
| 600 seconds (10 minutes) |
| .It 10m |
| 10 minutes |
| .It 1h30m |
| 1 hour 30 minutes (90 minutes) |
| .El |
| .Sh FILES |
| .Bl -tag -width Ds |
| .It Pa /etc/ssh/sshd_config |
| Contains configuration data for |
| .Nm sshd . |
| This file should be writable by root only, but it is recommended |
| (though not necessary) that it be world-readable. |
| .El |
| .Sh SEE ALSO |
| .Xr sshd 8 |
| .Sh 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 versions 1.5 and 2.0. |
| Niels Provos and Markus Friedl contributed support |
| for privilege separation. |