SSHD_CONFIG(5) File Formats Manual SSHD_CONFIG(5) NAME sshd_config -- OpenSSH daemon configuration file DESCRIPTION sshd(8) reads configuration data from /etc/ssh/sshd_config (or the file specified with -f on the command line). The file contains keyword-argument pairs, one per line. Unless noted otherwise, for each keyword, the first obtained value will be used. Lines starting with `#' and empty lines are interpreted as comments. Arguments may optionally be enclosed in double quotes (") 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): AcceptEnv Specifies what environment variables sent by the client will be copied into the session's environ(7). See SendEnv and SetEnv in ssh_config(5) for how to configure the client. The TERM environ- ment variable is always accepted whenever the client requests a pseudo-terminal as it is required by the protocol. Variables are specified by name, which may contain the wildcard characters `*' and `?'. Multiple environment variables may be separated by white- space or spread across multiple AcceptEnv directives. Be warned that some environment variables could be used to bypass restricted user environments. For this reason, care should be taken in the use of this directive. The default is not to accept any environ- ment variables. AddressFamily Specifies which address family should be used by sshd(8). Valid arguments are any (the default), inet (use IPv4 only), or inet6 (use IPv6 only). AllowAgentForwarding Specifies whether ssh-agent(1) forwarding is permitted. The de- fault is yes. Note that disabling agent forwarding does not im- prove security unless users are also denied shell access, as they can always install their own forwarders. AllowGroups This keyword can be followed by a list of group name patterns, sep- arated by spaces. If specified, login is allowed only for users whose primary group or supplementary 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 all groups. AllowGroups is not consulted for groups matched by DenyGroups. See PATTERNS in ssh_config(5) for more information on patterns. This keyword may appear multiple times in sshd_config with each in- stance appending to the list. AllowStreamLocalForwarding Specifies whether StreamLocal (Unix-domain socket) forwarding is permitted. The available options are yes (the default) or all to allow StreamLocal forwarding, no to prevent all StreamLocal for- warding, local to allow local (from the perspective of ssh(1)) for- warding only or remote to allow remote forwarding only. Note that disabling StreamLocal forwarding does not improve security unless users are also denied shell access, as they can always install their own forwarders. AllowTcpForwarding Specifies whether TCP forwarding is permitted. The available op- tions are yes (the default) or all to allow TCP forwarding, no to prevent all TCP forwarding, local to allow local (from the perspec- tive of ssh(1)) forwarding only or remote to allow remote forward- ing only. Note that disabling TCP forwarding does not improve se- curity unless users are also denied shell access, as they can al- ways install their own forwarders. AllowUsers This keyword can be followed by a list of user name patterns, sepa- rated by spaces. If specified, login is allowed only for user names that match one of 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. HOST criteria may additionally con- tain addresses to match in CIDR address/masklen format. AllowUsers is not consulted for users matched by DenyUsers. See PATTERNS in ssh_config(5) for more information on patterns. This keyword may appear multiple times in sshd_config with each in- stance appending to the list. AuthenticationMethods Specifies the authentication methods that must be successfully com- pleted for a user to be granted access. This option must be fol- lowed by one or more lists of comma-separated authentication method names, or by the single string any to indicate the default behav- iour of accepting any single authentication method. If the default is overridden, then successful authentication requires completion of every method in at least one of these lists. For example, "publickey,password publickey,keyboard-interactive" would require the user to complete public key authentication, fol- lowed by either password or keyboard interactive authentication. Only methods that are next in one or more lists are offered at each stage, so for this example it would not be possible to attempt password or keyboard-interactive authentication before public key. For keyboard interactive authentication it is also possible to re- strict authentication to a specific device by appending a colon followed by the device identifier bsdauth or pam. depending on the server configuration. For example, "keyboard-interactive:bsdauth" would restrict keyboard interactive authentication to the bsdauth device. If the publickey method is listed more than once, sshd(8) verifies that keys that have been used successfully are not reused for sub- sequent authentications. For example, "publickey,publickey" re- quires successful authentication using two different public keys. Note that each authentication method listed should also be explic- itly enabled in the configuration. The available authentication methods are: "gssapi-with-mic", "hostbased", "keyboard-interactive", "none" (used for access to password-less accounts when PermitEmptyPasswords is enabled), "password" and "publickey". AuthorizedKeysCommand Specifies a program to be used to look up the user's public keys. The program must be owned by root, not writable by group or others and specified by an absolute path. Arguments to AuthorizedKeysCommand accept the tokens described in the "TOKENS" section. If no arguments are specified then the username of the target user is used. The program should produce on standard output zero or more lines of authorized_keys output (see AUTHORIZED_KEYS in sshd(8)). AuthorizedKeysCommand is tried after the usual AuthorizedKeysFile files and will not be executed if a matching key is found there. By default, no AuthorizedKeysCommand is run. This command is only executed for valid users. AuthorizedKeysCommandUser Specifies the user under whose account the AuthorizedKeysCommand is run. It is recommended to use a dedicated user that has no other role on the host than running authorized keys commands. If AuthorizedKeysCommand is specified but AuthorizedKeysCommandUser is not, then sshd(8) will refuse to start. AuthorizedKeysFile Specifies the file that contains the public keys used for user au- thentication. The format is described in the AUTHORIZED_KEYS FILE FORMAT section of sshd(8). Arguments to AuthorizedKeysFile may in- clude wildcards and accept the tokens described in the "TOKENS" section. After expansion, AuthorizedKeysFile is taken to be an ab- solute path or one relative to the user's home directory. Multiple files may be listed, separated by whitespace. Alternately this op- tion may be set to none to skip checking for user keys in files. The default is ".ssh/authorized_keys .ssh/authorized_keys2". These files are only checked for valid users. AuthorizedPrincipalsCommand Specifies a program to be used to generate the list of allowed cer- tificate principals as per AuthorizedPrincipalsFile. The program must be owned by root, not writable by group or others and speci- fied by an absolute path. Arguments to AuthorizedPrincipalsCommand accept the tokens described in the "TOKENS" section. If no argu- ments are specified then the username of the target user is used. The program should produce on standard output zero or more lines of AuthorizedPrincipalsFile output. If either AuthorizedPrincipalsCommand or AuthorizedPrincipalsFile is speci- fied, then certificates offered by the client for authentication must contain a principal that is listed. By default, no AuthorizedPrincipalsCommand is run. This command is only executed for valid users. AuthorizedPrincipalsCommandUser Specifies the user under whose account the AuthorizedPrincipalsCommand is run. It is recommended to use a dedicated user that has no other role on the host than running au- thorized principals commands. If AuthorizedPrincipalsCommand is specified but AuthorizedPrincipalsCommandUser is not, then sshd(8) will refuse to start. AuthorizedPrincipalsFile Specifies a file that lists principal names that are accepted for certificate authentication. When using certificates signed by a key listed in TrustedUserCAKeys, this file lists names, one of which must appear in the certificate for it to be accepted for au- thentication. Names are listed one per line preceded by key op- tions (as described in AUTHORIZED_KEYS FILE FORMAT in sshd(8)). Empty lines and comments starting with `#' are ignored. Arguments to AuthorizedPrincipalsFile may include wildcards and ac- cept the tokens described in the "TOKENS" section. After expan- sion, AuthorizedPrincipalsFile is taken to be an absolute path or one relative to the user's home directory. The default is none, i.e. not to use a principals file - in this case, the username of the user must appear in a certificate's principals list for it to be accepted. This file is only checked for valid users. Note that AuthorizedPrincipalsFile is only used when authentication proceeds using a CA listed in TrustedUserCAKeys and is not con- sulted for certification authorities trusted via ~/.ssh/authorized_keys, though the principals= key option offers a similar facility (see sshd(8) for details). Banner The contents of the specified file are sent to the remote user be- fore authentication is allowed. If the argument is none then no banner is displayed. By default, no banner is displayed. CASignatureAlgorithms Specifies which algorithms are allowed for signing of certificates by certificate authorities (CAs). The default is: ssh-ed25519,ecdsa-sha2-nistp256, ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, sk-ssh-ed25519@openssh.com, sk-ecdsa-sha2-nistp256@openssh.com, rsa-sha2-512,rsa-sha2-256 If the specified list begins with a `+' character, then the speci- fied algorithms will be appended to the default set instead of re- placing them. If the specified list begins with a `-' character, then the specified algorithms (including wildcards) will be removed from the default set instead of replacing them. Certificates signed using other algorithms will not be accepted for public key or host-based authentication. ChannelTimeout Specifies whether and how quickly sshd(8) should close inactive channels. Timeouts are specified as one or more "type=interval" pairs separated by whitespace, where the "type" must be the special keyword "global" or a channel type name from the list below, op- tionally containing wildcard characters. The timeout value "interval" is specified in seconds or may use any of the units documented in the "TIME FORMATS" section. For exam- ple, "session=5m" would cause interactive sessions to terminate af- ter five minutes of inactivity. Specifying a zero value disables the inactivity timeout. The special timeout "global" applies to all active channels, taken together. Traffic on any active channel will reset the timeout, but when the timeout expires then all open channels will be closed. Note that this global timeout is not matched by wildcards and must be specified explicitly. The available channel type names include: agent-connection Open connections to ssh-agent(1). direct-tcpip, direct-streamlocal@openssh.com Open TCP or Unix socket (respectively) connections that have been established from an ssh(1) local forwarding, i.e. LocalForward or DynamicForward. forwarded-tcpip, forwarded-streamlocal@openssh.com Open TCP or Unix socket (respectively) connections that have been established to an sshd(8) listening on behalf of an ssh(1) remote forwarding, i.e. RemoteForward. session The interactive main session, including shell session, com- mand execution, scp(1), sftp(1), etc. tun-connection Open TunnelForward connections. x11-connection Open X11 forwarding sessions. Note that in all the above cases, terminating an inactive session does not guarantee to remove all resources associated with the ses- sion, e.g. shell processes or X11 clients relating to the session may continue to execute. Moreover, terminating an inactive channel or session does not nec- essarily close the SSH connection, nor does it prevent a client from requesting another channel of the same type. In particular, expiring an inactive forwarding session does not prevent another identical forwarding from being subsequently created. The default is not to expire channels of any type for inactivity. ChrootDirectory Specifies the pathname of a directory to chroot(2) to after authen- tication. At session startup sshd(8) checks that all components of the pathname are root-owned directories which are not writable by group or others. After the chroot, sshd(8) changes the working di- rectory to the user's home directory. Arguments to ChrootDirectory accept the tokens described in the "TOKENS" section. The ChrootDirectory must contain the necessary files and directo- ries to support the user's session. For an interactive session this requires at least a shell, typically sh(1), and basic /dev nodes such as null(4), zero(4), stdin(4), stdout(4), stderr(4), and tty(4) devices. For file transfer sessions using SFTP no addi- tional configuration of the environment is necessary if the in- process sftp-server is used, though sessions which use logging may require /dev/log inside the chroot directory on some operating sys- tems (see sftp-server(8) for details). For safety, it is very important that the directory hierarchy be prevented from modification by other processes on the system (espe- cially those outside the jail). Misconfiguration can lead to un- safe environments which sshd(8) cannot detect. The default is none, indicating not to chroot(2). Ciphers Specifies the ciphers allowed. Multiple ciphers must be comma-sep- arated. If the specified list begins with a `+' character, then the specified ciphers will be appended to the default set instead of replacing them. If the specified list begins with a `-' charac- ter, then the specified ciphers (including wildcards) will be re- moved from the default set instead of replacing them. If the spec- ified list begins with a `^' character, then the specified ciphers will be placed at the head of the default set. The supported ciphers are: 3des-cbc aes128-cbc aes192-cbc aes256-cbc aes128-ctr aes192-ctr aes256-ctr aes128-gcm@openssh.com aes256-gcm@openssh.com chacha20-poly1305@openssh.com The default is: chacha20-poly1305@openssh.com, aes128-gcm@openssh.com,aes256-gcm@openssh.com, aes128-ctr,aes192-ctr,aes256-ctr The list of available ciphers may also be obtained using "ssh -Q cipher". ClientAliveCountMax Sets the number of client alive messages which may be sent without sshd(8) receiving any messages back from the client. If this threshold is reached while client alive messages are being sent, sshd will disconnect the client, terminating the session. It is important to note that the use of client alive messages is very different from TCPKeepAlive. The client alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option enabled by TCPKeepAlive is spoofable. The client alive mechanism is valuable when the client or server depend on knowing when a connection has become unresponsive. The default value is 3. If ClientAliveInterval is set to 15, and ClientAliveCountMax is left at the default, unresponsive SSH clients will be disconnected after approximately 45 seconds. Set- ting a zero ClientAliveCountMax disables connection termination. 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 to request a response from the client. The de- fault is 0, indicating that these messages will not be sent to the client. Compression Specifies whether compression is enabled after the user has authen- ticated successfully. The argument must be yes, delayed (a legacy synonym for yes) or no. The default is yes. DenyGroups This keyword can be followed by a list of group name patterns, sep- arated by spaces. Login is disallowed for users whose primary group or supplementary 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 all groups. AllowGroups is not consulted for groups matched by DenyGroups. See PATTERNS in ssh_config(5) for more information on patterns. This keyword may appear multiple times in sshd_config with each in- stance appending to the list. DenyUsers This keyword can be followed by a list of user name patterns, sepa- rated by spaces. Login is disallowed for user names that match one of 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 sepa- rately checked, restricting logins to particular users from partic- ular hosts. HOST criteria may additionally contain addresses to match in CIDR address/masklen format. AllowUsers is not consulted for users matched by DenyUsers. See PATTERNS in ssh_config(5) for more information on patterns. This keyword may appear multiple times in sshd_config with each in- stance appending to the list. DisableForwarding Disables all forwarding features, including X11, ssh-agent(1), TCP and StreamLocal. This option overrides all other forwarding-re- lated options and may simplify restricted configurations. ExposeAuthInfo Writes a temporary file containing a list of authentication methods and public credentials (e.g. keys) used to authenticate the user. The location of the file is exposed to the user session through the SSH_USER_AUTH environment variable. The default is no. FingerprintHash Specifies the hash algorithm used when logging key fingerprints. Valid options are: md5 and sha256. The default is sha256. ForceCommand Forces the execution of the command specified by ForceCommand, ig- noring any command supplied by the client and ~/.ssh/rc if present. The command is 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 Match block. The command originally supplied by the client is available in the SSH_ORIGINAL_COMMAND en- vironment 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. The default is none. This directive does not limit other kinds of access that a client may request via their connection, such as TCP, agent, socket or X11 forwarding. If these are not desired, then they must be explicitly disabled, either individually via their respective options or all together using the DisableForwarding option. GatewayPorts Specifies whether remote hosts are allowed to connect to ports for- warded for the client. By default, sshd(8) binds remote port for- wardings to the loopback address. This prevents other remote hosts from connecting to forwarded ports. GatewayPorts can be used to specify that sshd should allow remote port forwardings to bind to non-loopback addresses, thus allowing other hosts to connect. The argument may be no to force remote port forwardings to be available to the local host only, yes to force remote port forwardings to bind to the wildcard address, or clientspecified to allow the client to select the address to which the forwarding is bound. The default is no. GSSAPIAuthentication Specifies whether user authentication based on GSSAPI is allowed. The default is no. GSSAPICleanupCredentials Specifies whether to automatically destroy the user's credentials cache on logout. The default is yes. GSSAPIDelegateCredentials Accept delegated credentials on the server side. The default is yes. GSSAPIStrictAcceptorCheck Determines whether to be strict about the identity of the GSSAPI acceptor a client authenticates against. If set to yes then the client must authenticate against the host service on the current hostname. If set to no then the client may authenticate against any service key stored in the machine's default store. This facil- ity is provided to assist with operation on multi homed machines. The default is yes. HostbasedAcceptedAlgorithms Specifies the signature algorithms that will be accepted for host- based authentication as a list of comma-separated patterns. Alter- nately if the specified list begins with a `+' character, then the specified signature algorithms will be appended to the default set instead of replacing them. If the specified list begins with a `-' character, then the specified signature algorithms (including wild- cards) will be removed from the default set instead of replacing them. If the specified list begins with a `^' character, then the specified signature algorithms will be placed at the head of the default set. The default for this option is: ssh-ed25519-cert-v01@openssh.com, ecdsa-sha2-nistp256-cert-v01@openssh.com, ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com, sk-ssh-ed25519-cert-v01@openssh.com, sk-ecdsa-sha2-nistp256-cert-v01@openssh.com, webauthn-sk-ecdsa-sha2-nistp256-cert-v01@openssh.com, rsa-sha2-512-cert-v01@openssh.com, rsa-sha2-256-cert-v01@openssh.com, ssh-ed25519, ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, sk-ssh-ed25519@openssh.com, sk-ecdsa-sha2-nistp256@openssh.com, webauthn-sk-ecdsa-sha2-nistp256@openssh.com, rsa-sha2-512,rsa-sha2-256 The list of available signature algorithms may also be obtained us- ing "ssh -Q HostbasedAcceptedAlgorithms". This was formerly named HostbasedAcceptedKeyTypes. HostbasedAuthentication Specifies whether rhosts or /etc/hosts.equiv authentication to- gether with successful public key client host authentication is al- lowed (host-based authentication). The default is no. HostbasedUsesNameFromPacketOnly Specifies whether or not the server will attempt to perform a re- verse 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 than attempting to resolve the name from the TCP connection itself. The default is no. HostCertificate Specifies a file containing a public host certificate. The cer- tificate's public key must match a private host key already speci- fied by HostKey. The default behaviour of sshd(8) is not to load any certificates. HostKey Specifies a file containing a private host key used by SSH. The defaults are /etc/ssh/ssh_host_ecdsa_key, /etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key. Note that sshd(8) will refuse to use a file if it is group/world- accessible and that the HostKeyAlgorithms option restricts which of the keys are actually used by sshd(8). It is possible to have multiple host key files. It is also possi- ble to specify public host key files instead. In this case opera- tions on the private key will be delegated to an ssh-agent(1). HostKeyAgent Identifies the UNIX-domain socket used to communicate with an agent that has access to the private host keys. If the string "SSH_AUTH_SOCK" is specified, the location of the socket will be read from the SSH_AUTH_SOCK environment variable. HostKeyAlgorithms Specifies the host key signature algorithms that the server offers. The default for this option is: ssh-ed25519-cert-v01@openssh.com, ecdsa-sha2-nistp256-cert-v01@openssh.com, ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com, sk-ssh-ed25519-cert-v01@openssh.com, sk-ecdsa-sha2-nistp256-cert-v01@openssh.com, webauthn-sk-ecdsa-sha2-nistp256-cert-v01@openssh.com, rsa-sha2-512-cert-v01@openssh.com, rsa-sha2-256-cert-v01@openssh.com, ssh-ed25519, ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, sk-ssh-ed25519@openssh.com, sk-ecdsa-sha2-nistp256@openssh.com, webauthn-sk-ecdsa-sha2-nistp256@openssh.com, rsa-sha2-512,rsa-sha2-256 The list of available signature algorithms may also be obtained us- ing "ssh -Q HostKeyAlgorithms". IgnoreRhosts Specifies whether to ignore per-user .rhosts and .shosts files dur- ing HostbasedAuthentication. The system-wide /etc/hosts.equiv and /etc/shosts.equiv are still used regardless of this setting. Accepted values are yes (the default) to ignore all per-user files, shosts-only to allow the use of .shosts but to ignore .rhosts or no to allow both .shosts and rhosts. IgnoreUserKnownHosts Specifies whether sshd(8) should ignore the user's ~/.ssh/known_hosts during HostbasedAuthentication and use only the system-wide known hosts file /etc/ssh/ssh_known_hosts. The default is "no". Include Include the specified configuration file(s). Multiple pathnames may be specified and each pathname may contain glob(7) wildcards that will be expanded and processed in lexical order. Files with- out absolute paths are assumed to be in /etc/ssh. An Include di- rective may appear inside a Match block to perform conditional in- clusion. IPQoS Specifies the Differentiated Services Field Codepoint (DSCP) value for the connection. Accepted values are af11, af12, af13, af21, af22, af23, af31, af32, af33, af41, af42, af43, cs0, cs1, cs2, cs3, cs4, cs5, cs6, cs7, ef, le, a numeric value, or none to use the op- erating system default. This option may take one or two arguments, separated by whitespace. If one argument is specified, it is used as the packet class unconditionally. If two values are specified, the first is automatically selected for interactive sessions and the second for non-interactive sessions. The default is ef (Expe- dited Forwarding) for interactive sessions and none (the operating system default) for non-interactive sessions. KbdInteractiveAuthentication Specifies whether to allow keyboard-interactive authentication. All authentication styles from login.conf(5) are supported. The default is yes. The argument to this keyword must be yes or no. ChallengeResponseAuthentication is a deprecated alias for this. KerberosAuthentication Specifies whether the password provided by the user for PasswordAuthentication will be validated through the Kerberos KDC. To use this option, the server needs a Kerberos servtab which al- lows 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 ac- quire 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. The default is yes. KerberosTicketCleanup Specifies whether to automatically destroy the user's ticket cache file on logout. The default is yes. KexAlgorithms Specifies the permitted KEX (Key Exchange) algorithms that the server will offer to clients. The ordering of this list is not im- portant, as the client specifies the preference order. Multiple algorithms must be comma-separated. If the specified list begins with a `+' character, then the speci- fied algorithms will be appended to the default set instead of re- placing them. If the specified list begins with a `-' character, then the specified algorithms (including wildcards) will be removed from the default set instead of replacing them. If the specified list begins with a `^' character, then the specified algorithms will be placed at the head of the default set. The supported algorithms are: curve25519-sha256 curve25519-sha256@libssh.org diffie-hellman-group1-sha1 diffie-hellman-group14-sha1 diffie-hellman-group14-sha256 diffie-hellman-group16-sha512 diffie-hellman-group18-sha512 diffie-hellman-group-exchange-sha1 diffie-hellman-group-exchange-sha256 ecdh-sha2-nistp256 ecdh-sha2-nistp384 ecdh-sha2-nistp521 mlkem768x25519-sha256 sntrup761x25519-sha512 sntrup761x25519-sha512@openssh.com The default is: mlkem768x25519-sha256, sntrup761x25519-sha512,sntrup761x25519-sha512@openssh.com, curve25519-sha256,curve25519-sha256@libssh.org, ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521 The list of supported key exchange algorithms may also be obtained using "ssh -Q KexAlgorithms". ListenAddress Specifies the local addresses sshd(8) should listen on. The fol- lowing forms may be used: ListenAddress hostname|address [rdomain domain] ListenAddress hostname:port [rdomain domain] ListenAddress IPv4_address:port [rdomain domain] ListenAddress [hostname|address]:port [rdomain domain] The optional rdomain qualifier requests sshd(8) listen in an ex- plicit routing domain. If port is not specified, sshd will listen on the address and all Port options specified. The default is to listen on all local addresses on the current default routing do- main. Multiple ListenAddress options are permitted. For more in- formation on routing domains, see rdomain(4). LoginGraceTime The server disconnects after this time if the user has not success- fully 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, VER- BOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. DE- BUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of debugging output. Logging with a DEBUG level vio- lates the privacy of users and is not recommended. LogVerbose Specify one or more overrides to LogLevel. An override consists of one or more pattern lists that matches the source file, function and line number to force detailed logging for. For example, an override pattern of: kex.c:*:1000,*:kex_exchange_identification():*,packet.c:* would enable detailed logging for line 1000 of kex.c, everything in the kex_exchange_identification() function, and all code in the packet.c file. This option is intended for debugging and no over- rides are enabled by default. MACs Specifies the available MAC (message authentication code) algo- rithms. The MAC algorithm is used for data integrity protection. Multiple algorithms must be comma-separated. If the specified list begins with a `+' character, then the specified algorithms will be appended to the default set instead of replacing them. If the specified list begins with a `-' character, then the specified al- gorithms (including wildcards) will be removed from the default set instead of replacing them. If the specified list begins with a `^' character, then the specified algorithms will be placed at the head of the default set. The algorithms that contain "-etm" calculate the MAC after encryp- tion (encrypt-then-mac). These are considered safer and their use recommended. The supported MACs are: hmac-md5 hmac-md5-96 hmac-sha1 hmac-sha1-96 hmac-sha2-256 hmac-sha2-512 umac-64@openssh.com umac-128@openssh.com hmac-md5-etm@openssh.com hmac-md5-96-etm@openssh.com hmac-sha1-etm@openssh.com hmac-sha1-96-etm@openssh.com hmac-sha2-256-etm@openssh.com hmac-sha2-512-etm@openssh.com umac-64-etm@openssh.com umac-128-etm@openssh.com The default is: umac-64-etm@openssh.com,umac-128-etm@openssh.com, hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com, hmac-sha1-etm@openssh.com, umac-64@openssh.com,umac-128@openssh.com, hmac-sha2-256,hmac-sha2-512,hmac-sha1 The list of available MAC algorithms may also be obtained using "ssh -Q mac". Match Introduces a conditional block. If all of the criteria on the Match line are satisfied, the keywords on the following lines over- ride those set in the global section of the config file, until ei- ther another Match line or the end of the file. If a keyword ap- pears in multiple Match blocks that are satisfied, only the first instance of the keyword is applied. The arguments to Match are one or more criteria-pattern pairs or one of the single token criteria: All, which matches all criteria, or Invalid-User, which matches when the requested user-name does not match any known account. The available criteria are User, Group, Host, LocalAddress, LocalPort, Version, RDomain, and Address (with RDomain representing the rdomain(4) on which the connection was received). The match patterns may consist of single entries or comma-separated lists and may use the wildcard and negation operators described in the "PATTERNS" section of ssh_config(5). The patterns in an Address criteria may additionally contain ad- dresses to match in CIDR address/masklen format, such as 192.0.2.0/24 or 2001:db8::/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 the address 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. The Version keyword matches against the version string of sshd(8), for example "OpenSSH_10.0". Only a subset of keywords may be used on the lines following a Match keyword. Available keywords are AcceptEnv, AllowAgentForwarding, AllowGroups, AllowStreamLocalForwarding, AllowTcpForwarding, AllowUsers, AuthenticationMethods, AuthorizedKeysCommand, AuthorizedKeysCommandUser, AuthorizedKeysFile, AuthorizedPrincipalsCommand, AuthorizedPrincipalsCommandUser, AuthorizedPrincipalsFile, Banner, CASignatureAlgorithms, ChannelTimeout, ChrootDirectory, ClientAliveCountMax, ClientAliveInterval, DenyGroups, DenyUsers, DisableForwarding, ExposeAuthInfo, ForceCommand, GatewayPorts, GSSAPIAuthentication, HostbasedAcceptedAlgorithms, HostbasedAuthentication, HostbasedUsesNameFromPacketOnly, IgnoreRhosts, Include, IPQoS, KbdInteractiveAuthentication, KerberosAuthentication, LogLevel, MaxAuthTries, MaxSessions, PasswordAuthentication, PermitEmptyPasswords, PermitListen, PermitOpen, PermitRootLogin, PermitTTY, PermitTunnel, PermitUserRC, PubkeyAcceptedAlgorithms, PubkeyAuthentication, PubkeyAuthOptions, RefuseConnection, RekeyLimit, RevokedKeys, RDomain, SetEnv, StreamLocalBindMask, StreamLocalBindUnlink, TrustedUserCAKeys, UnusedConnectionTimeout, 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 are logged. The default is 6. MaxSessions Specifies the maximum number of open shell, login or subsystem (e.g. sftp) sessions permitted per network connection. Multiple sessions may be established by clients that support connection mul- tiplexing. Setting MaxSessions to 1 will effectively disable ses- sion multiplexing, whereas setting it to 0 will prevent all shell, login and subsystem sessions while still permitting forwarding. The default is 10. MaxStartups Specifies the maximum number of concurrent unauthenticated connec- tions to the SSH daemon. Additional connections will be dropped until authentication succeeds or the LoginGraceTime expires for a connection. Alternatively, random early drop can be enabled by specifying the three colon separated values start:rate:full (e.g. "10:30:60"). The default is 10:30:100. sshd(8) will refuse connection attempts with a probability of rate/100 (30%) if there are currently start (10) unauthenticated connections. The probability increases lin- early and all connection attempts are refused if the number of unauthenticated connections reaches full (60). ModuliFile Specifies the moduli(5) file that contains the Diffie-Hellman groups used for the "diffie-hellman-group-exchange-sha1" and "diffie-hellman-group-exchange-sha256" key exchange methods. The default is /etc/moduli. 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. PermitListen Specifies the addresses/ports on which a remote TCP port forwarding may listen. The listen specification must be one of the following forms: PermitListen port PermitListen host:port Multiple permissions may be specified by separating them with whitespace. An argument of any can be used to remove all restric- tions and permit any listen requests. An argument of none can be used to prohibit all listen requests. The host name may contain wildcards as described in the PATTERNS section in ssh_config(5). The wildcard `*' can also be used in place of a port number to al- low all ports. By default all port forwarding listen requests are permitted. Note that the GatewayPorts option may further restrict which addresses may be listened on. Note also that ssh(1) will re- quest a listen host of "localhost" if no listen host was specifi- cally requested, and this name is treated differently to explicit localhost addresses of "127.0.0.1" and "::1". PermitOpen Specifies the destinations to which TCP port forwarding is permit- ted. The forwarding specification must be one of the following forms: PermitOpen host:port PermitOpen IPv4_addr:port PermitOpen [IPv6_addr]:port Multiple forwards may be specified by separating them with white- space. An argument of any can be used to remove all restrictions and permit any forwarding requests. An argument of none can be used to prohibit all forwarding requests. The wildcard `*' can be used for host or port to allow all hosts or ports respectively. Otherwise, no pattern matching or address lookups are performed on supplied names. By default all port forwarding requests are per- mitted. PermitRootLogin Specifies whether root can log in using ssh(1). The argument must be yes, prohibit-password, forced-commands-only, or no. The de- fault is prohibit-password. If this option is set to prohibit-password (or its deprecated alias, without-password), password and keyboard-interactive authen- tication are disabled for root. If this option is set to forced-commands-only, root login with pub- lic key authentication will be allowed, but only if the command op- tion has been specified (which may be useful for taking remote backups even if root login is normally not allowed). All other au- thentication methods are disabled for root. If this option is set to no, root is not allowed to log in. PermitTTY Specifies whether pty(4) allocation is permitted. The default is yes. PermitTunnel Specifies whether tun(4) device forwarding is allowed. The argu- ment 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. Independent of this setting, the permissions of the selected tun(4) device must allow access to the user. PermitUserEnvironment Specifies whether ~/.ssh/environment and environment= options in ~/.ssh/authorized_keys are processed by sshd(8). Valid options are yes, no or a pattern-list specifying which environment variable names to accept (for example "LANG,LC_*"). The default is no. En- abling environment processing may enable users to bypass access re- strictions in some configurations using mechanisms such as LD_PRELOAD. PermitUserRC Specifies whether any ~/.ssh/rc file is executed. The default is yes. PerSourceMaxStartups Specifies the number of unauthenticated connections allowed from a given source address, or "none" if there is no limit. This limit is applied in addition to MaxStartups, whichever is lower. The de- fault is none. PerSourceNetBlockSize Specifies the number of bits of source address that are grouped to- gether for the purposes of applying PerSourceMaxStartups limits. Values for IPv4 and optionally IPv6 may be specified, separated by a colon. The default is 32:128, which means each address is con- sidered individually. PerSourcePenalties Controls penalties for various conditions that may represent at- tacks on sshd(8). If a penalty is enforced against a client then its source address and any others in the same network, as defined by PerSourceNetBlockSize, will be refused connection for a period. A penalty doesn't affect concurrent connections in progress, but multiple penalties from the same source from concurrent connections will accumulate up to a maximum. Conversely, penalties are not ap- plied until a minimum threshold time has been accumulated. Penalties are enabled by default with the default settings listed below but may disabled using the no keyword. The defaults may be overridden by specifying one or more of the keywords below, sepa- rated by whitespace. All keywords accept arguments, e.g. "crash:2m". crash:duration Specifies how long to refuse clients that cause a crash of sshd(8)(default: 90s). authfail:duration Specifies how long to refuse clients that disconnect after making one or more unsuccessful authentication attempts (default: 5s). invaliduser:duration Specifies how long to refuse clients that attempt to log in with an invalid user (default: 5s). refuseconnection:duration Specifies how long to refuse clients that were administra- tively prohibited connection via the RefuseConnection op- tion (default: 10s). noauth:duration Specifies how long to refuse clients that disconnect with- out attempting authentication (default: 1s). This timeout should be used cautiously otherwise it may penalise legiti- mate scanning tools such as ssh-keyscan(1). grace-exceeded:duration Specifies how long to refuse clients that fail to authenti- cate after LoginGraceTime (default: 10s). max:duration Specifies the maximum time a particular source address range will be refused access for (default: 10m). Repeated penalties will accumulate up to this maximum. min:duration Specifies the minimum penalty that must accrue before en- forcement begins (default: 15s). max-sources4:number, max-sources6:number Specifies the maximum number of client IPv4 and IPv6 ad- dress ranges to track for penalties (default: 65536 for both). overflow:mode Controls how the server behaves when max-sources4 or max-sources6 is exceeded. There are two operating modes: deny-all, which denies all incoming connections other than those exempted via PerSourcePenaltyExemptList until a penalty expires, and permissive, which allows new connec- tions by removing existing penalties early (default: per- missive). Note that client penalties below the min thresh- old count against the total number of tracked penalties. IPv4 and IPv6 addresses are tracked separately, so an over- flow in one will not affect the other. overflow6:mode Allows specifying a different overflow mode for IPv6 ad- dresses. The default it to use the same overflow mode as was specified for IPv4. PerSourcePenaltyExemptList Specifies a comma-separated list of addresses to exempt from penal- ties. This list may contain wildcards and CIDR address/masklen ranges. 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 the address 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, respec- tively. The default is not to exempt any addresses. PidFile Specifies the file that contains the process ID of the SSH daemon, or none to not write one. 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 also ListenAddress. 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. PubkeyAcceptedAlgorithms Specifies the signature algorithms that will be accepted for public key authentication as a list of comma-separated patterns. Alter- nately if the specified list begins with a `+' character, then the specified algorithms will be appended to the default set instead of replacing them. If the specified list begins with a `-' character, then the specified algorithms (including wildcards) will be removed from the default set instead of replacing them. If the specified list begins with a `^' character, then the specified algorithms will be placed at the head of the default set. The default for this option is: ssh-ed25519-cert-v01@openssh.com, ecdsa-sha2-nistp256-cert-v01@openssh.com, ecdsa-sha2-nistp384-cert-v01@openssh.com, ecdsa-sha2-nistp521-cert-v01@openssh.com, sk-ssh-ed25519-cert-v01@openssh.com, sk-ecdsa-sha2-nistp256-cert-v01@openssh.com, webauthn-sk-ecdsa-sha2-nistp256-cert-v01@openssh.com, rsa-sha2-512-cert-v01@openssh.com, rsa-sha2-256-cert-v01@openssh.com, ssh-ed25519, ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, sk-ssh-ed25519@openssh.com, sk-ecdsa-sha2-nistp256@openssh.com, webauthn-sk-ecdsa-sha2-nistp256@openssh.com, rsa-sha2-512,rsa-sha2-256 The list of available signature algorithms may also be obtained us- ing "ssh -Q PubkeyAcceptedAlgorithms". PubkeyAuthOptions Sets one or more public key authentication options. The supported keywords are: none (the default; indicating no additional options are enabled), touch-required and verify-required. The touch-required option causes public key authentication using a FIDO authenticator algorithm (i.e. ecdsa-sk or ed25519-sk) to al- ways require the signature to attest that a physically present user explicitly confirmed the authentication (usually by touching the authenticator). By default, sshd(8) requires user presence unless overridden with an authorized_keys option. The touch-required flag disables this override. The verify-required option requires a FIDO key signature attest that the user was verified, e.g. via a PIN. Neither the touch-required or verify-required options have any ef- fect for other, non-FIDO, public key types. PubkeyAuthentication Specifies whether public key authentication is allowed. The de- fault is yes. RefuseConnection Indicates that sshd(8) should unconditionally terminate the connec- tion. Additionally, a refuseconnection penalty may be recorded against the source of the connection if PerSourcePenalties are en- abled. This option is only really useful in a Match block. RekeyLimit Specifies the maximum amount of data that may be transmitted or re- ceived before the session key is renegotiated, optionally followed by a maximum amount of time that may pass before the session key is renegotiated. The first argument is specified in bytes and may have a suffix of `K', `M', or `G' to indicate Kilobytes, Megabytes, or Gigabytes, respectively. The default is between `1G' and `4G', depending on the cipher. The optional second value is specified in seconds and may use any of the units documented in the "TIME FORMATS" section. The default value for RekeyLimit is default none, which means that rekeying is performed after the cipher's de- fault amount of data has been sent or received and no time based rekeying is done. RequiredRSASize Specifies the minimum RSA key size (in bits) that sshd(8) will ac- cept. User and host-based authentication keys smaller than this limit will be refused. The default is 1024 bits. Note that this limit may only be raised from the default. RevokedKeys Specifies revoked public keys file, or none to not use one. Keys listed in this file will be refused for public key authentication. Note that if this file is not readable, then public key authentica- tion will be refused for all users. Keys may be specified as a text file, listing one public key per line, or as an OpenSSH Key Revocation List (KRL) as generated by ssh-keygen(1). This file may be consulted for each public key authentication attempt received by sshd(8) and its contents must be consistent at all times, therefore it should only be atomically replaced and never modified in place while the server is running. For more information on KRLs, see the KEY REVOCATION LISTS section in ssh-keygen(1). RDomain Specifies an explicit routing domain that is applied after authen- tication has completed. The user session, as well as any forwarded or listening IP sockets, will be bound to this rdomain(4). If the routing domain is set to %D, then the domain in which the incoming connection was received will be applied. SecurityKeyProvider Specifies a path to a library that will be used when loading FIDO authenticator-hosted keys, overriding the default of using the built-in USB HID support. SetEnv Specifies one or more environment variables to set in child ses- sions started by sshd(8) as "NAME=VALUE". The environment value may be quoted (e.g. if it contains whitespace characters). Envi- ronment variables set by SetEnv override the default environment and any variables specified by the user via AcceptEnv or PermitUserEnvironment. SshdAuthPath Overrides the default path to the sshd-auth binary that is invoked to complete user authentication. The default is /usr/libexec/sshd-auth. This option is intended for use by tests. SshdSessionPath Overrides the default path to the sshd-session binary that is in- voked to handle each connection. The default is /usr/libexec/sshd-session. This option is intended for use by tests. StreamLocalBindMask Sets the octal file creation mode mask (umask) used when creating a Unix-domain socket file for local or remote port forwarding. This option is only used for port forwarding to a Unix-domain socket file. The default value is 0177, which creates a Unix-domain socket file that is readable and writable only by the owner. Note that not all operating systems honor the file mode on Unix-domain socket files. StreamLocalBindUnlink Specifies whether to remove an existing Unix-domain socket file for local or remote port forwarding before creating a new one. If the socket file already exists and StreamLocalBindUnlink is not en- abled, sshd will be unable to forward the port to the Unix-domain socket file. This option is only used for port forwarding to a Unix-domain socket file. The argument must be yes or no. The default is no. 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 desirable because novices sometimes accidentally leave their directory or files world-writable. The default is yes. Note that this does not apply to ChrootDirectory, whose permissions and ownership are checked unconditionally. Subsystem Configures an external subsystem (e.g. file transfer daemon). Ar- guments should be a subsystem name and a command (with optional ar- guments) to execute upon subsystem request. The command sftp-server implements the SFTP file transfer subsys- tem. Alternately the name internal-sftp implements an in-process SFTP server. This may simplify configurations using ChrootDirectory to force a different filesystem root on clients. It accepts the same command line arguments as sftp-server and even though it is in- process, settings such as LogLevel or SyslogFacility do not apply to it and must be set explicitly via command line arguments. By default no subsystems are defined. SyslogFacility Gives the facility code that is used when logging messages from sshd(8). The possible values are: DAEMON, USER, AUTH, LOCAL0, LO- CAL1, 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 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 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 avoids infinitely hanging sessions. To disable TCP keepalive messages, the value should be set to no. TrustedUserCAKeys Specifies a file containing public keys of certificate authorities that are trusted to sign user certificates for authentication, or none to not use one. Keys are listed one per line; empty lines and comments starting with `#' are allowed. If a certificate is pre- sented for authentication and has its signing CA key listed in this file, then it may be used for authentication for any user listed in the certificate's principals list. Note that certificates that lack a list of principals will not be permitted for authentication using TrustedUserCAKeys. For more details on certificates, see the CERTIFICATES section in ssh-keygen(1). UnusedConnectionTimeout Specifies whether and how quickly sshd(8) should close client con- nections with no open channels. Open channels include active shell, command execution or subsystem sessions, connected network, socket, agent or X11 forwardings. Forwarding listeners, such as those from the ssh(1) -R flag, are not considered as open channels and do not prevent the timeout. The timeout value is specified in seconds or may use any of the units documented in the "TIME FORMATS" section. Note that this timeout starts when the client connection completes user authentication but before the client has an opportunity to open any channels. Caution should be used when using short timeout values, as they may not provide sufficient time for the client to request and open its channels before terminating the connection. The default none is to never expire connections for having no open channels. This option may be useful in conjunction with ChannelTimeout. UseDNS Specifies whether sshd(8) should look up the remote host name, and to check that the resolved host name for the remote IP address maps back to the very same IP address. If this option is set to no (the default) then only addresses and not host names may be used in ~/.ssh/authorized_keys from and sshd_config Match Host directives. VersionAddendum Optionally specifies additional text to append to the SSH protocol banner sent by the server upon connection. The default is none. X11DisplayOffset Specifies the first display number available for sshd(8)'s X11 for- warding. This prevents sshd from interfering with real X11 servers. The default is 10. X11Forwarding Specifies whether X11 forwarding is permitted. The 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 listen on the wildcard address (see X11UseLocalhost), though this is not the default. Additionally, the authentication spoofing and authentication data verification and substitution oc- cur 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 ForwardX11 in ssh_config(5)). A system administrator may have a stance in which they want to protect clients that may expose them- selves to attack by unwittingly requesting X11 forwarding, which can warrant a no setting. Note that disabling X11 forwarding does not prevent users from for- warding X11 traffic, as users can always install their own for- warders. 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 forwarding server to the loopback address and sets the hostname part of the DISPLAY environment variable to localhost. This prevents remote hosts from connecting to the proxy display. However, some older X11 clients may not function with this configu- ration. X11UseLocalhost may be set to no to specify that the for- warding server should be bound to the wildcard address. The argu- ment must be yes or no. The default is yes. XAuthLocation Specifies the full pathname of the xauth(1) program, or none to not use one. The default is /usr/X11R6/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: <none> seconds s | S seconds m | M minutes h | H hours d | D days w | W weeks Each member of the sequence is added together to calculate the total time value. Time format examples: 600 600 seconds (10 minutes) 10m 10 minutes 1h30m 1 hour 30 minutes (90 minutes) TOKENS Arguments to some keywords can make use of tokens, which are expanded at runtime. Tokens are expanded without quoting or escaping of shell charac- ters. It is the administrator's responsibility to ensure they are safe in the context of their use. The supported tokens in sshd_config are: %% A literal `%'. %C Identifies the connection endpoints, containing four space-sep- arated values: client address, client port number, server ad- dress, and server port number. %D The routing domain in which the incoming connection was re- ceived. %F The fingerprint of the CA key. %f The fingerprint of the key or certificate. %h The home directory of the user. %i The key ID in the certificate. %K The base64-encoded CA key. %k The base64-encoded key or certificate for authentication. %s The serial number of the certificate. %T The type of the CA key. %t The key or certificate type. %U The numeric user ID of the target user. %u The username. AuthorizedKeysCommand accepts the tokens %%, %C, %D, %f, %h, %k, %t, %U, and %u. AuthorizedKeysFile accepts the tokens %%, %h, %U, and %u. AuthorizedPrincipalsCommand accepts the tokens %%, %C, %D, %F, %f, %h, %i, %K, %k, %s, %T, %t, %U, and %u. AuthorizedPrincipalsFile accepts the tokens %%, %h, %U, and %u. ChrootDirectory accepts the tokens %%, %h, %U, and %u. RoutingDomain accepts the token %D. FILES /etc/ssh/sshd_config Contains configuration data for sshd(8). This file should be writable by root only, but it is recommended (though not necessary) that it be world-readable. SEE ALSO sftp-server(8), 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 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 privi- lege separation. OpenBSD 7.9 March 28, 2026 SSHD_CONFIG(5)
NAME | DESCRIPTION | TIME FORMATS | TOKENS | FILES | SEE ALSO | AUTHORS
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