Sshd Default Config



The default is /usr/X11/bin/xauth and sshd attempts to open it when X11 forwarding is enabled. Sshd command-line arguments and configuration file options that specify time can be expressed using a sequence of the form: timequalifier, where time is a positive integer value and qualifier is one of the following: seconds. The OpenSSH sshd command has an extended test switch which can be used to 'Check the validity of the configuration file, output the effective configuration to stdout and then exit.' (source sshd man page). So the answer is (as root, or prefixing it with sudo): sshd -T (the settings are not in alphabetical order, one can use sshd -T sort to quickly look for one setting, or just grep the.

Name

sshd_config - OpenSSH SSH daemon configuration file

Synopsis

  • Echo 'PasswordAuthentication no' /etc/ssh/sshdconfig && echo 'ChallengeResponseAuthentication no' /etc/ssh/sshdconfig. If you added Linux-PAM support and you want ssh to use it then you will need to add a configuration file for sshd and enable use of LinuxPAM. Note, ssh only uses PAM to check passwords, if you've disabled password logins these commands are not needed.
  • The /etc/ssh/sshdconfig file is the system-wide configuration file for OpenSSH which allows you to set options that modify the operation of the daemon. This file contains keyword-value pairs, one per line, with keywords being case insensitive.

/etc/ssh/sshd_config

Description

sshd(8) reads configuration data from /etc/ssh/sshd_config (or the file specified with -f on the command line). The file containskeyword-argument pairs, one per line. Lines starting with '#' and empty lines are interpreted as comments. Arguments may optionally be enclosed in doublequotes (') in order to represent arguments containing spaces.

The possible keywords and their meanings are as follows (note that keywords are case-insensitive and arguments are case-sensitive):

Specifies what environment variables sent by the client will be copied into the session's environ(7). See SendEnv in ssh_config(5) for how toconfigure the client. Note that environment passing is only supported for protocol 2. Variables are specified by name, which may contain the wildcardcharacters '*' and '?'. Multiple environment variables may be separated by whitespace or spread across multiple AcceptEnv directives. Be warned thatsome environment variables could be used to bypass restricted user environments. For this reason, care should be taken in the use of this directive. Thedefault is not to accept any environment variables.

AddressFamily
Specifies which address family should be used by sshd(8). Valid arguments are 'any', 'inet' (use IPv4 only), or 'inet6' (use IPv6 only). The default is'any'.

AllowAgentForwarding
Specifies whether ssh-agent(1) forwarding is permitted. The default is 'yes'. Note that disabling agent forwarding does not improve security unless users arealso denied shell access, as they can always install their own forwarders.

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 orsupplementary group list matches one of the patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is allowed for allgroups. The allow/deny directives are processed in the following order: DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.

See PATTERNS in ssh_config(5) for more information on patterns.

AllowTcpForwarding
Specifies whether TCP forwarding is permitted. The default is 'yes'. Note that disabling TCP forwarding does not improve security unless users are alsodenied 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 user names that match one of thepatterns. 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@HOSTthen USER and HOST are separately checked, restricting logins to particular users from particular hosts. The allow/deny directives are processed in thefollowing order: DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.

See PATTERNS in ssh_config(5) for more information on patterns.

AuthorizedKeysFile
Specifies the file that contains the public keys that can be used for user authentication. AuthorizedKeysFile may contain tokens of the form %T whichare substituted during connection setup. The following tokens are defined: %% is replaced by a literal '%', %h is replaced by the home directory of the userbeing authenticated, and %u is replaced by the username of that user. After expansion, AuthorizedKeysFile is taken to be an absolute path or onerelative to the user's home directory. The default is '.ssh/authorized_keys'.

Banner
The contents of the specified file are sent to the remote user before authentication is allowed. If the argument is 'none' then no banner is displayed. Thisoption is only available for protocol version 2. By default, no banner is displayed.

ChallengeResponseAuthentication
Specifies whether challenge-response authentication is allowed (e.g. via PAM or though authentication styles supported in login.conf(5)) The default is'yes'.

ChrootDirectory
Specifies a path to chroot(2) to after authentication. This path, and all its components, must be root-owned directories that are not writable by any otheruser or group. After the chroot, sshd(8) changes the working directory to the user's home directory.

The path may contain the following tokens that are expanded at runtime once the connecting user has been authenticated: %% is replaced by a literal '%', %his replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user.

The ChrootDirectory must contain the necessary files and directories to support the user's session. For an interactive session this requires at leasta shell, typically sh(1), and basic /dev nodes such as null(4), zero(4), stdin(4), stdout(4), stderr(4), arandom(4) and tty(4) devices. For filetransfer sessions using 'sftp', no additional configuration of the environment is necessary if the in-process sftp server is used, though sessions which uselogging do require /dev/log inside the chroot directory (see sftp-server(8) for details).

The default is not to chroot(2).

Ciphers
Specifies the ciphers allowed for protocol version 2. Multiple ciphers must be comma-separated. The supported ciphers are '3des-cbc', 'aes128-cbc','aes192-cbc', 'aes256-cbc', 'aes128-ctr', 'aes192-ctr', 'aes256-ctr', 'arcfour128', 'arcfour256', 'arcfour', 'blowfish-cbc', and'cast128-cbc'. The default is:

aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
aes256-cbc,arcfour

Sets the number of client alive messages (see below) which may be sent without sshd(8) receiving any messages back from the client. If this threshold isreached while client alive messages are being sent, sshd will disconnect the client, terminating the session. It is important to note that the use of clientalive messages is very different from TCPKeepAlive (below). The client alive messages are sent through the encrypted channel and therefore will not bespoofable. The TCP keepalive option enabled by TCPKeepAlive is spoofable. The client alive mechanism is valuable when the client or server depend onknowing when a connection has become inactive.

The default value is 3. If ClientAliveInterval (see below) is set to 15, and ClientAliveCountMax is left at the default, unresponsive SSHclients will be disconnected after approximately 45 seconds. This option applies to protocol version 2 only.

ClientAliveInterval
Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a message through the encrypted channel torequest 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 2only.

Compression
Specifies whether compression is allowed, or delayed until the user has authenticated successfully. The argument must be 'yes', 'delayed', or 'no'. Thedefault is 'delayed'.

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 grouplist matches one of the patterns. Only group names are valid; a numerical group ID is not recognized. By default, login is allowed for all groups. Theallow/deny directives are processed in the following order: DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.

See PATTERNS in ssh_config(5) for more information on patterns.

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. Only usernames 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 HOSTare separately checked, restricting logins to particular users from particular hosts. The allow/deny directives are processed in the following order:DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups.

See PATTERNS in ssh_config(5) for more information on patterns.

ForceCommand
Forces the execution of the command specified by ForceCommand, ignoring any command supplied by the client and ~/.ssh/rc if present. The commandis invoked by using the user's login shell with the -c option. This applies to shell, command, or subsystem execution. It is most useful inside a Matchblock. The command originally supplied by the client is available in the SSH_ORIGINAL_COMMAND environment variable. Specifying a command of 'internal-sftp'will force the use of an in-process sftp server that requires no support files when used with ChrootDirectory.

GatewayPorts
Specifies whether remote hosts are allowed to connect to ports forwarded for the client. By default, sshd(8) binds remote port forwardings to the loopbackaddress. This prevents other remote hosts from connecting to forwarded ports. GatewayPorts can be used to specify that sshd should allow remote portforwardings to bind to non-loopback addresses, thus allowing other hosts to connect. The argument may be 'no' to force remote port forwardings to beavailable to the local host only, 'yes' to force remote port forwardings to bind to the wildcard address, or 'clientspecified' to allow the client toselect the address to which the forwarding is bound. The default is 'no'.

Dvd factory free download. GSSAPIAuthentication
Specifies whether user authentication based on GSSAPI is allowed. The default is 'no'. Note that this option applies to protocol version 2 only.

GSSAPIKeyExchange
Specifies whether key exchange based on GSSAPI is allowed. GSSAPI key exchange doesn't rely on ssh keys to verify host identity. The default is 'no'. Notethat this option applies to protocol version 2 only.

GSSAPICleanupCredentials
Specifies whether to automatically destroy the user's credentials cache on logout. The default is 'yes'. Note that this option applies to protocol version 2only.

GSSAPIStrictAcceptorCheck
Determines whether to be strict about the identity of the GSSAPI acceptor a client authenticates against. If 'yes' then the client must authenticate againstthe host service on the current hostname. If 'no' then the client may authenticate against any service key stored in the machine's default store. Thisfacility is provided to assist with operation on multi homed machines. The default is 'yes'. Note that this option applies only to protocol version 2 GSSAPIconnections, and setting it to 'no' may only work with recent Kerberos GSSAPI libraries.

GSSAPIStoreCredentialsOnRekey
Controls whether the user's GSSAPI credentials should be updated following a successful connection rekeying. This option can be used to accepted renewed orupdated credentials from a compatible client. The default is 'no'.

HostbasedAuthentication
Specifies whether rhosts or /etc/hosts.equiv authentication together with successful public key client host authentication is allowed (host-basedauthentication). This option is similar to RhostsRSAAuthentication and applies to protocol version 2 only. The default is 'no'.

Config

HostbasedUsesNameFromPacketOnly
Specifies whether or not the server will attempt to perform a reverse name lookup when matching the name in the ~/.shosts, ~/.rhosts, and/etc/hosts.equiv files during HostbasedAuthentication. A setting of 'yes' means that sshd(8) uses the name supplied by the client rather thanattempting to resolve the name from the TCP connection itself. 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 protocol version 2. Note that sshd(8) will refuse to use a file if it isgroup/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 ofthe SSH protocol.

IgnoreRhosts
Specifies that .rhosts and .shosts files will not be used in RhostsRSAAuthentication or HostbasedAuthentication.

/etc/hosts.equiv and /etc/ssh/shosts.equiv are still used. The default is 'yes'.

IgnoreUserKnownHosts
Specifies whether sshd(8) should ignore the user's ~/.ssh/known_hosts during RhostsRSAAuthentication or HostbasedAuthentication. Thedefault is 'no'.

KerberosAuthentication
Specifies whether the password provided by the user for PasswordAuthentication will be validated through the Kerberos KDC. To use this option, theserver needs a Kerberos servtab which allows the verification of the KDC's identity. The default is 'no'.

KerberosGetAFSToken
If AFS is active and the user has a Kerberos 5 TGT, attempt to acquire an AFS token before accessing the user's home directory. The default is 'no'.

KerberosOrLocalPasswd
If password authentication through Kerberos fails then the password will be validated via any additional local mechanism such as /etc/passwd. Thedefault is 'yes'.

KerberosTicketCleanup
Specifies whether to automatically destroy the user's ticket cache file on logout. The default is 'yes'.

KerberosUseKuserok
Specifies whether to look at .k5login file for user's aliases. The 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 toprevent 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 isnever regenerated. The default is 3600 (seconds).

ListenAddress
Specifies the local addresses sshd(8) should listen on. The following forms may be used:

ListenAddresshost|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 localaddresses. Multiple ListenAddress options are permitted. Additionally, any Port options must precede this option for non-port qualifiedaddresses.

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.

LogLevel
Gives the verbosity level that is used when logging messages from sshd(8). 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 levelviolates the privacy of users and is not recommended.

MACs' Specifies the available MAC (message authentication code) algorithms. The MAC algorithm is used in protocol version 2 for data integrityprotection. Multiple algorithms must be comma-separated. The default is:

hmac-md5,hmac-sha1,umac-64@openssh.com,
hmac-ripemd160,hmac-sha1-96,hmac-md5-96

Introduces a conditional block. If all of the criteria on the Match line are satisfied, the keywords on the following lines override those set in theglobal section of the config file, until either another Match line or the end of the file.

The arguments to Match are one or more criteria-pattern pairs. The available criteria are User, Group, Host, and Address.The match patterns may consist of single entries or comma-separated lists and may use the wildcard and negation operators described in the PATTERNSsection of ssh_config(5).

The patterns in an Address criteria may additionally contain addresses to match in CIDR address/masklen format, e.g. '192.0.2.0/24' or'3ffe:ffff::/32'. Note that the mask length provided must be consistent with the address - it is an error to specify a mask length that is too long for theaddress or one with bits set in this host portion of the address. For example, '192.0.2.0/33' and '192.0.2.0/8' respectively.

Only a subset of keywords may be used on the lines following a Match keyword. Available keywords are AllowAgentForwarding,AllowTcpForwarding, Banner, ChrootDirectory, ForceCommand, GatewayPorts, GSSAPIAuthentication,HostbasedAuthentication, KbdInteractiveAuthentication, KerberosAuthentication, KerberosUseKuserok, MaxAuthTries,MaxSessions, PubkeyAuthentication, AuthorizedKeysCommand, AuthorizedKeysCommandRunAs, PasswordAuthentication,PermitEmptyPasswords, PermitOpen, PermitRootLogin, RequiredAuthentications1, RequiredAuthentications2, RhostsRSAAuthentication,RSAAuthentication, X11DisplayOffset, X11Forwarding and X11UseLocalHost.

MaxAuthTries
Specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures arelogged. The default is 6.

MaxSessions
Specifies the maximum number of open sessions permitted per network connection. The default is 10.

MaxStartups
Specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeedsor 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(8) will refuseconnection attempts with a probability of 'rate/100' (30%) if there are currently 'start' (10) unauthenticated connections. The probability increaseslinearly and all connection attempts are refused if the number of unauthenticated connections reaches 'full' (60).

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'.

PermitOpen
Specifies the destinations to which TCP port forwarding is permitted. The forwarding specification must be one of the following forms:

PermitOpenhost:port
PermitOpen
IPv4_addr:port
PermitOpen
[IPv6_addr]:port

Multiple forwards may be specified by separating them with whitespace. An argument of 'any' can be used to remove all restrictions and permit anyforwarding requests. By default all port forwarding requests are permitted.

PermitRootLogin
Specifies whether root can log in 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 authentication 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 beenspecified (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 log in.

PermitTunnel
Specifies whether tun(4) device forwarding is allowed. The argument must be 'yes', 'point-to-point' (layer 3), 'ethernet' (layer 2), or 'no'.Specifying 'yes' permits both 'point-to-point' and 'ethernet'. The default is 'no'.

PermitUserEnvironment
Specifies whether ~/.ssh/environment and environment= options in ~/.ssh/authorized_keys are processed by sshd(8). The default is 'no'.Enabling environment processing may enable users to bypass access restrictions in some configurations using mechanisms such as LD_PRELOAD.

PidFile
Specifies the file that contains the process ID of the SSH daemon. The default is /var/run/sshd.pid.

Port' Specifies the port number that sshd(8) listens on. The default is 22. Multiple options of this type are permitted. See alsoListenAddress.

PrintLastLog
Specifies whether sshd(8) should print the date and time of the last user login when a user logs in interactively. The default is 'yes'.

PrintMotd
Specifies whether sshd(8) 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'.

Protocol
Specifies the protocol versions sshd(8) supports. The possible values are '1' and '2'. Multiple versions must be comma-separated. The default is '2,1'. Notethat the order of the protocol list does not indicate preference, because the client selects among multiple protocol versions offered by the server. Specifying'2,1' is identical to '1,2'.

PubkeyAuthentication
Specifies whether public key authentication is allowed. The default is 'yes'. Note that this option applies to protocol version 2 only.

AuthorizedKeysCommand
Specifies a program to be used for lookup of the user's public keys. The program will be invoked with its first argument the name of the user being authorized,and should produce on standard output AuthorizedKeys lines (see AUTHORIZED_KEYS in sshd(8)). By default (or when set to the empty string) there is noAuthorizedKeysCommand run. If the AuthorizedKeysCommand does not successfully authorize the user, authorization falls through to the AuthorizedKeysFile. Notethat this option has an effect only with PubkeyAuthentication turned on.

AuthorizedKeysCommandRunAs
Specifies the user under whose account the AuthorizedKeysCommand is run. Empty string (the default value) means the user being authorized is used.

RequiredAuthentications[12]
Specifies required methods of authentications that has to succeed before authorizing the connection. (RequiredAuthentication1 for Protocol version 1, andRequiredAuthentication2 for v2)

RequiredAuthentications1 method[,method..]
RequiredAuthentications2 method[,method..]

Example 1:Example 2:Available methods:

Specifies whether rhosts or /etc/hosts.equiv authentication together with successful RSA host authentication is allowed. The default is 'no'. This optionapplies 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 1024.

ShowPatchLevel
Specifies whether sshd will display the patch level of the binary in the identification string. The patch level is set at compile-time. The default is'no'. This option applies to protocol version 1 only.

StrictModes
Specifies whether sshd(8) should check file modes and ownership of the user's files and home directory before accepting login. This is normally desirablebecause 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 (with optional arguments) to execute uponsubsystem request.

The command sftp-server(8) implements the 'sftp' file transfer subsystem.

Alternately the name 'internal-sftp' implements an in-process 'sftp' server. This may simplify configurations using ChrootDirectory to force adifferent filesystem root on clients.

By default no subsystems are defined. Note that this option applies to protocol version 2 only.

SyslogFacility
Gives the facility code that is used when logging messages from sshd(8). The possible values are: DAEMON, USER, AUTH, AUTHPRIV, LOCAL0, LOCAL1, LOCAL2, LOCAL3,LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH.

TCPKeepAlive
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 machineswill 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 TCP keepalives are not sent, sessions may hang indefinitely on the server, leaving 'ghost' users and consuming server resources.

The default is 'yes' (to send TCP keepalive messages), and the server will notice if the network goes down or the client host crashes. This avoidsinfinitely hanging sessions.

To disable TCP keepalive messages, the value should be set to 'no'.

UseDNS
Specifies whether sshd(8) should look up the remote host name and check that the resolved host name for the remote IP address maps back to the very same IPaddress. The default is 'yes'.

UseLogin
Specifies whether login(1) is used for interactive login sessions. The default is 'no'. Note that login(1) is never used for remote command execution. Notealso, that if this is enabled, X11Forwarding will be disabled because login(1) does not know how to handle xauth(1) cookies. IfUsePrivilegeSeparation is specified, it will be disabled after authentication.

UsePAM
Enables the Pluggable Authentication Module interface. If set to 'yes' this will enable PAM authentication using ChallengeResponseAuthentication andPasswordAuthentication in addition to PAM account and session module processing for all authentication types.

Because PAM challenge-response authentication usually serves an equivalent role to password authentication, you should disable eitherPasswordAuthentication or ChallengeResponseAuthentication.

If UsePAM is enabled, you will not be able to run sshd(8) as a non-root user. The default is 'no'.

UsePrivilegeSeparation
Specifies whether sshd(8) separates privileges by creating an unprivileged child process to deal with incoming network traffic. After successfulauthentication, another process will be created that has the privilege of the authenticated user. The goal of privilege separation is to prevent privilegeescalation by containing any corruption within the unprivileged processes. The default is 'yes'.

X11DisplayOffset
Specifies the first display number available for sshd(8)'s X11 forwarding. This prevents sshd from interfering with real X11 servers. The default is 10.

X11Forwarding
Specifies whether X11 forwarding is permitted. The argument must be 'yes' or 'no'. The default is 'no'.

When X11 forwarding is enabled, there may be additional exposure to the server and to client displays if the sshd(8) proxy display is configured to listenon the wildcard address (see X11UseLocalhost below), though this is not the default. Additionally, the authentication spoofing and authentication dataverification 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 toattack when the SSH client requests forwarding (see the warnings for ForwardX11 in ssh_config(5)). A system administrator may have a stance in whichthey want to protect clients that may expose themselves to attack by unwittingly requesting X11 forwarding, which can warrant a 'no' setting.

Note that disabling X11 forwarding does not prevent users from forwarding X11 traffic, as users can always install their own forwarders. X11 forwarding isautomatically disabled if UseLogin is enabled.

X11UseLocalhost
Specifies whether sshd(8) should bind the X11 forwarding server to the loopback address or to the wildcard address. By default, sshd binds the forwardingserver to the loopback address and sets the hostname part of the DISPLAY environment variable to 'localhost'. This prevents remote hosts from connecting tothe proxy display. However, some older X11 clients may not function with this configuration. X11UseLocalhost may be set to 'no' to specify that theforwarding server should be bound to the wildcard address. The argument must be 'yes' or 'no'. The default is 'yes'.

XAuthLocation
Specifies the full pathname of the xauth(1) program. The default is /usr/bin/xauth.

Time Formats

sshd(8) 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 following:

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
1h30m
1 hour 30 minutes (90 minutes)

Files

Contains configuration data for sshd

Ssh Config File Example

(8). This file should be writable by root only, but it is recommended (though not necessary) that it be world-readable.

See Also

sshd(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 andDug 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. NielsProvos and Markus Friedl contributed support for privilege separation.

BSD April 14, 2013 BSD

Referenced By

brlapi_tty(3),gsissh(1),gsissh_config(5),gsisshd(8),ssh-add(1),ssh-ldap-helper

Default Sshd Config File

(8),sss_ssh_authorizedkeys

Default Associations Windows 10

(1)