neulab/tldr huggingface dataset:
Normally this program generates the key and asks for a file in which to store the private key.  The public key is stored in a file with the same name but “.pub” appended.  The program also asks for a passphrase.  The passphrase may be empty to indicate no passphrase (host keys must have an empty passphrase), or it may be a string of arbitrary length.  A passphrase is similar to a password, except it can be a phrase with a series of words, punctuation, numbers, whitespace, or any string of characters you want. Good passphrases are 10-30 characters long, are not simple sentences or otherwise easily guessable (English prose has only 1-2 bits of entropy per character, and provides very bad passphrases), and contain a mix of upper and lowercase letters, numbers, and non-alphanumeric characters.  The passphrase can be changed later by using the -p option.
There is no way to recover a lost passphrase.  If the passphrase is lost or forgotten, a new key must be generated and the corresponding public key copied to other machines.
ssh-keygen will by default write keys in an OpenSSH-specific format.  This format is preferred as it offers better protection for keys at rest as well as allowing storage of key comments within the private key file itself. The key comment may be useful to help identify the key.  The comment is initialized to “user@host” when the key is created, but can be changed using the -c option.
It is still possible for ssh-keygen to write the previously-used PEM format private keys using the -m flag.  This may be used when generating new keys, and existing new-format keys may be converted using this option in conjunction with the -p (change passphrase) flag.
After a key is generated, ssh-keygen will ask where the keys should be placed to be activated.
-A      For each of the key types (rsa, dsa, ecdsa and ed25519) for which host keys do not exist, generate the host keys with the default key file path, an empty passphrase, default bits for the key type, and default comment.  If -f has also been specified, its argument is used as a prefix to the default path for the resulting host key files.  This is used by /etc/rc to generate new host keys.
-a rounds When saving a private key, this option specifies the number of KDF (key derivation function, currently bcrypt_pbkdf(3)) rounds used. Higher numbers result in slower passphrase verification and increased resistance to brute-force password cracking (should the keys be stolen).  The default is 16 rounds.
-B      Show the bubblebabble digest of specified private or public key file.
-b bits Specifies the number of bits in the key to create.  For RSA keys, the minimum size is 1024 bits and the default is 3072 bits. Generally, 3072 bits is considered sufficient.  DSA keys must be exactly 1024 bits as specified by FIPS 186-2.  For ECDSA keys, the -b flag determines the key length by selecting from one of three elliptic curve sizes: 256, 384 or 521 bits.  Attempting to use bit lengths other than these three values for ECDSA keys will fail. ECDSA-SK, Ed25519 and Ed25519-SK keys have a fixed length and the -b flag will be ignored.
-C comment Provides a new comment.
-c      Requests changing the comment in the private and public key files. The program will prompt for the file containing the private keys, for the passphrase if the key has one, and for the new comment.
-D pkcs11 Download the public keys provided by the PKCS#11 shared library pkcs11.  When used in combination with -s, this option indicates that a CA key resides in a PKCS#11 token (see the CERTIFICATES section for details).
-e      This option will read a private or public OpenSSH key file and print to stdout a public key in one of the formats specified by the -m option.  The default export format is “RFC4716”.  This option allows exporting OpenSSH keys for use by other programs, including several commercial SSH implementations.
-F hostname | [hostname]:port Search for the specified hostname (with optional port number) in a known_hosts file, listing any occurrences found.  This option is useful to find hashed host names or addresses and may also be used in conjunction with the -H option to print found keys in a hashed format.
-f filename Specifies the filename of the key file.
-g      Use generic DNS format when printing fingerprint resource records using the -r command.
-H      Hash a known_hosts file.  This replaces all hostnames and addresses with hashed representations within the specified file; the original content is moved to a file with a .old suffix.  These hashes may be used normally by ssh and sshd, but they do not reveal identifying information should the file's contents be disclosed.  This option will not modify existing hashed hostnames and is therefore safe to use on files that mix hashed and non-hashed names.
-h      When signing a key, create a host certificate instead of a user certificate.  Please see the CERTIFICATES section for details.
-I certificate_identity Specify the key identity when signing a public key.  Please see the CERTIFICATES section for details.
-i      This option will read an unencrypted private (or public) key file in the format specified by the -m option and print an OpenSSH compatible private (or public) key to stdout.  This option allows importing keys from other software, including several commercial SSH implementations.  The default import format is “RFC4716”.
-K      Download resident keys from a FIDO authenticator.  Public and private key files will be written to the current directory for each downloaded key.  If multiple FIDO authenticators are attached, keys will be downloaded from the first touched authenticator.
-k      Generate a KRL file.  In this mode, ssh-keygen will generate a KRL file at the location specified via the -f flag that revokes every key or certificate presented on the command line. Keys/certificates to be revoked may be specified by public key file or using the format described in the KEY REVOCATION LISTS section.
-L      Prints the contents of one or more certificates.
-l      Show fingerprint of specified public key file.  For RSA and DSA keys ssh-keygen tries to find the matching public key file and prints its fingerprint.  If combined with -v, a visual ASCII art representation of the key is supplied with the fingerprint.
-M generate Generate candidate Diffie-Hellman Group Exchange (DH-GEX) parameters for eventual use by the ‘diffie-hellman-group-exchange-*’ key exchange methods.  The numbers generated by this operation must be further screened before use.  See the MODULI GENERATION section for more information.
-M screen Screen candidate parameters for Diffie-Hellman Group Exchange. This will accept a list of candidate numbers and test that they are safe (Sophie Germain) primes with acceptable group generators.  The results of this operation may be added to the /etc/ssh/moduli file. See the MODULI GENERATION section for more information.
-m key_format Specify a key format for key generation, the -i (import), -e (export) conversion options, and the -p change passphrase operation.  The latter may be used to convert between OpenSSH private key and PEM private key formats.  The supported key formats are: “RFC4716” (RFC 4716/SSH2 public or private key), “PKCS8” (PKCS8 public or private key) or “PEM” (PEM public key).  By default OpenSSH will write newly-generated private keys in its own format, but when converting public keys for export the default format is “RFC4716”.  Setting a format of “PEM” when generating or updating a supported private key type will cause the key to be stored in the legacy PEM private key format.
-N new_passphrase Provides the new passphrase.
-n principals Specify one or more principals (user or host names) to be included in a certificate when signing a key.  Multiple principals may be specified, separated by commas.  Please see the CERTIFICATES section for details.
-O option Specify a key/value option.  These are specific to the operation that ssh-keygen has been requested to perform.
When signing certificates, one of the options listed in the CERTIFICATES section may be specified here.
When performing moduli generation or screening, one of the options listed in the MODULI GENERATION section may be specified.
When generating a key that will be hosted on a FIDO authenticator, this flag may be used to specify key-specific options.  Those supported at present are:
application Override the default FIDO application/origin string of “ssh:”.  This may be useful when generating host or domain- specific resident keys.  The specified application string must begin with “ssh:”.
challenge=path Specifies a path to a challenge string that will be passed to the FIDO token during key generation.  The challenge string may be used as part of an out-of-band protocol for key enrollment (a random challenge is used by default).
device  Explicitly specify a fido(4) device to use, rather than letting the token middleware select one.
no-touch-required Indicate that the generated private key should not require touch events (user presence) when making signatures.  Note that sshd(8) will refuse such signatures by default, unless overridden via an authorized_keys option.
resident Indicate that the key should be stored on the FIDO authenticator itself.  Resident keys may be supported on FIDO2 tokens and typically require that a PIN be set on the token prior to generation.  Resident keys may be loaded off the token using ssh-add(1).
user    A username to be associated with a resident key, overriding the empty default username.  Specifying a username may be useful when generating multiple resident keys for the same application name.
verify-required Indicate that this private key should require user verification for each signature.  Not all FIDO tokens support this option.  Currently PIN authentication is the only supported verification method, but other methods may be supported in the future.
write-attestation=path May be used at key generation time to record the attestation data returned from FIDO tokens during key generation.  Please note that this information is potentially sensitive.  By default, this information is discarded.
When performing signature-related options using the -Y flag, the following options are accepted:
print-pubkey Print the full public key to standard output after signature verification.
verify-time=timestamp Specifies a time to use when validating signatures instead of the current time.  The time may be specified as a date in YYYYMMDD format or a time in YYYYMMDDHHMM[SS] format.
The -O option may be specified multiple times.
-P passphrase Provides the (old) passphrase.
-p      Requests changing the passphrase of a private key file instead of creating a new private key.  The program will prompt for the file containing the private key, for the old passphrase, and twice for the new passphrase.
-Q      Test whether keys have been revoked in a KRL.  If the -l option is also specified then the contents of the KRL will be printed.
-q      Silence ssh-keygen.
-R hostname | [hostname]:port Removes all keys belonging to the specified hostname (with optional port number) from a known_hosts file.  This option is useful to delete hashed hosts (see the -H option above).
-r hostname Print the SSHFP fingerprint resource record named hostname for the specified public key file.
-s ca_key Certify (sign) a public key using the specified CA key.  Please see the CERTIFICATES section for details.
When generating a KRL, -s specifies a path to a CA public key file used to revoke certificates directly by key ID or serial number. See the KEY REVOCATION LISTS section for details.
-t dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa Specifies the type of key to create.  The possible values are “dsa”, “ecdsa”, “ecdsa-sk”, “ed25519”, “ed25519-sk”, or “rsa”.
This flag may also be used to specify the desired signature type when signing certificates using an RSA CA key.  The available RSA signature variants are “ssh-rsa” (SHA1 signatures, not recommended), “rsa-sha2-256”, and “rsa-sha2-512” (the default).
-U      When used in combination with -s, this option indicates that a CA key resides in a ssh-agent(1).  See the CERTIFICATES section for more information.
-u      Update a KRL.  When specified with -k, keys listed via the command line are added to the existing KRL rather than a new KRL being created.
-V validity_interval Specify a validity interval when signing a certificate.  A validity interval may consist of a single time, indicating that the certificate is valid beginning now and expiring at that time, or may consist of two times separated by a colon to indicate an explicit time interval.
The start time may be specified as the string “always” to indicate the certificate has no specified start time, a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format, a relative time (to the current time) consisting of a minus sign followed by an interval in the format described in the TIME FORMATS section of sshd_config(5).
The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time, a relative time starting with a plus character or the string “forever” to indicate that the certificate has no expiry date.
For example: “+52w1d” (valid from now to 52 weeks and one day from now), “-4w:+4w” (valid from four weeks ago to four weeks from now), “20100101123000:20110101123000” (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011), “-1d:20110101” (valid from yesterday to midnight, January 1st, 2011), “-1m:forever” (valid from one minute ago and never expiring).
-v      Verbose mode.  Causes ssh-keygen to print debugging messages about its progress.  This is helpful for debugging moduli generation. Multiple -v options increase the verbosity.  The maximum is 3.
-w provider Specifies a path to a library that will be used when creating FIDO authenticator-hosted keys, overriding the default of using the internal USB HID support.
-Y find-principals Find the principal(s) associated with the public key of a signature, provided using the -s flag in an authorized signers file provided using the -f flag.  The format of the allowed signers file is documented in the ALLOWED SIGNERS section below.  If one or more matching principals are found, they are returned on standard output.
-Y check-novalidate Checks that a signature generated using ssh-keygen -Y sign has a valid structure.  This does not validate if a signature comes from an authorized signer.  When testing a signature, ssh-keygen accepts a message on standard input and a signature namespace using -n.  A file containing the corresponding signature must also be supplied using the -s flag.  Successful testing of the signature is signalled by ssh-keygen returning a zero exit status.
-Y sign Cryptographically sign a file or some data using a SSH key.  When signing, ssh-keygen accepts zero or more files to sign on the command-line - if no files are specified then ssh-keygen will sign data presented on standard input.  Signatures are written to the path of the input file with “.sig” appended, or to standard output if the message to be signed was read from standard input.
The key used for signing is specified using the -f option and may refer to either a private key, or a public key with the private half available via ssh-agent(1).  An additional signature namespace, used to prevent signature confusion across different domains of use (e.g. file signing vs email signing) must be provided via the -n flag.  Namespaces are arbitrary strings, and may include: “file” for file signing, “email” for email signing. For custom uses, it is recommended to use names following a NAMESPACE@YOUR.DOMAIN pattern to generate unambiguous namespaces.
-Y verify Request to verify a signature generated using ssh-keygen -Y sign as described above.  When verifying a signature, ssh-keygen accepts a message on standard input and a signature namespace using -n.  A file containing the corresponding signature must also be supplied using the -s flag, along with the identity of the signer using -I and a list of allowed signers via the -f flag.  The format of the allowed signers file is documented in the ALLOWED SIGNERS section below.  A file containing revoked keys can be passed using the -r flag.  The revocation file may be a KRL or a one-per-line list of public keys.  Successful verification by an authorized signer is signalled by ssh-keygen returning a zero exit status.
-y      This option will read a private OpenSSH format file and print an OpenSSH public key to stdout.
-Z cipher Specifies the cipher to use for encryption when writing an OpenSSH- format private key file.  The list of available ciphers may be obtained using "ssh -Q cipher".  The default is “aes256-ctr”.
-z serial_number Specifies a serial number to be embedded in the certificate to distinguish this certificate from others from the same CA.  If the serial_number is prefixed with a ‘+’ character, then the serial number will be incremented for each certificate signed on a single command-line.  The default serial number is zero.
When generating a KRL, the -z flag is used to specify a KRL version number.
ssh-keygen may be used to generate groups for the Diffie-Hellman Group Exchange (DH-GEX) protocol.  Generating these groups is a two-step process: first, candidate primes are generated using a fast, but memory intensive process.  These candidate primes are then tested for suitability (a CPU- intensive process).
Generation of primes is performed using the -M generate option.  The desired length of the primes may be specified by the -O bits option.  For example:
# ssh-keygen -M generate -O bits=2048 moduli-2048.candidates
By default, the search for primes begins at a random point in the desired length range.  This may be overridden using the -O start option, which specifies a different start point (in hex).
Once a set of candidates have been generated, they must be screened for suitability.  This may be performed using the -M screen option.  In this mode ssh-keygen will read candidates from standard input (or a file specified using the -f option).  For example:
# ssh-keygen -M screen -f moduli-2048.candidates moduli-2048
By default, each candidate will be subjected to 100 primality tests.  This may be overridden using the -O prime-tests option.  The DH generator value will be chosen automatically for the prime under consideration.  If a specific generator is desired, it may be requested using the -O generator option.  Valid generator values are 2, 3, and 5.
Screened DH groups may be installed in /etc/ssh/moduli.  It is important that this file contains moduli of a range of bit lengths.
A number of options are available for moduli generation and screening via the -O flag:
lines=number Exit after screening the specified number of lines while performing DH candidate screening.
start-line=line-number Start screening at the specified line number while performing DH candidate screening.
checkpoint=filename Write the last line processed to the specified file while performing DH candidate screening.  This will be used to skip lines in the input file that have already been processed if the job is restarted.
memory=mbytes Specify the amount of memory to use (in megabytes) when generating candidate moduli for DH-GEX.
start=hex-value Specify start point (in hex) when generating candidate moduli for DH-GEX.
generator=value Specify desired generator (in decimal) when testing candidate moduli for DH-GEX.
ssh-keygen supports signing of keys to produce certificates that may be used for user or host authentication.  Certificates consist of a public key, some identity information, zero or more principal (user or host) names and a set of options that are signed by a Certification Authority (CA) key. Clients or servers may then trust only the CA key and verify its signature on a certificate rather than trusting many user/host keys.  Note that OpenSSH certificates are a different, and much simpler, format to the X.509 certificates used in ssl(8).
ssh-keygen supports two types of certificates: user and host.  User certificates authenticate users to servers, whereas host certificates authenticate server hosts to users.  To generate a user certificate:
$ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
The resultant certificate will be placed in /path/to/user_key-cert.pub.  A host certificate requires the -h option:
$ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
The host certificate will be output to /path/to/host_key-cert.pub.
It is possible to sign using a CA key stored in a PKCS#11 token by providing the token library using -D and identifying the CA key by providing its public half as an argument to -s:
$ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
Similarly, it is possible for the CA key to be hosted in a ssh-agent(1). This is indicated by the -U flag and, again, the CA key must be identified by its public half.
$ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
In all cases, key_id is a "key identifier" that is logged by the server when the certificate is used for authentication.
Certificates may be limited to be valid for a set of principal (user/host) names.  By default, generated certificates are valid for all users or hosts.  To generate a certificate for a specified set of principals:
$ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub $ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub
Additional limitations on the validity and use of user certificates may be specified through certificate options.  A certificate option may disable features of the SSH session, may be valid only when presented from particular source addresses or may force the use of a specific command.
The options that are valid for user certificates are:
clear   Clear all enabled permissions.  This is useful for clearing the default set of permissions so permissions may be added individually.
critical:name[=contents] extension:name[=contents] Includes an arbitrary certificate critical option or extension. The specified name should include a domain suffix, e.g. “name@example.com”.  If contents is specified then it is included as the contents of the extension/option encoded as a string, otherwise the extension/option is created with no contents (usually indicating a flag).  Extensions may be ignored by a client or server that does not recognise them, whereas unknown critical options will cause the certificate to be refused.
force-command=command Forces the execution of command instead of any shell or command specified by the user when the certificate is used for authentication.
no-agent-forwarding Disable ssh-agent(1) forwarding (permitted by default).
no-port-forwarding Disable port forwarding (permitted by default).
no-pty  Disable PTY allocation (permitted by default).
no-user-rc Disable execution of ~/.ssh/rc by sshd(8) (permitted by default).
no-x11-forwarding Disable X11 forwarding (permitted by default).
permit-agent-forwarding Allows ssh-agent(1) forwarding.
permit-port-forwarding Allows port forwarding.
permit-pty Allows PTY allocation.
permit-user-rc Allows execution of ~/.ssh/rc by sshd(8).
permit-X11-forwarding Allows X11 forwarding.
no-touch-required Do not require signatures made using this key include demonstration of user presence (e.g. by having the user touch the authenticator). This option only makes sense for the FIDO authenticator algorithms ecdsa-sk and ed25519-sk.
source-address=address_list Restrict the source addresses from which the certificate is considered valid.  The address_list is a comma-separated list of one or more address/netmask pairs in CIDR format.
verify-required Require signatures made using this key indicate that the user was first verified.  This option only makes sense for the FIDO authenticator algorithms ecdsa-sk and ed25519-sk.  Currently PIN authentication is the only supported verification method, but other methods may be supported in the future.
At present, no standard options are valid for host keys.
Finally, certificates may be defined with a validity lifetime.  The -V option allows specification of certificate start and end times.  A certificate that is presented at a time outside this range will not be considered valid.  By default, certificates are valid from the UNIX Epoch to the distant future.
For certificates to be used for user or host authentication, the CA public key must be trusted by sshd(8) or ssh(1).  Please refer to those manual pages for details.
ssh-keygen is able to manage OpenSSH format Key Revocation Lists (KRLs). These binary files specify keys or certificates to be revoked using a compact format, taking as little as one bit per certificate if they are being revoked by serial number.
KRLs may be generated using the -k flag.  This option reads one or more files from the command line and generates a new KRL.  The files may either contain a KRL specification (see below) or public keys, listed one per line.  Plain public keys are revoked by listing their hash or contents in the KRL and certificates revoked by serial number or key ID (if the serial is zero or not available).
Revoking keys using a KRL specification offers explicit control over the types of record used to revoke keys and may be used to directly revoke certificates by serial number or key ID without having the complete original certificate on hand.  A KRL specification consists of lines containing one of the following directives followed by a colon and some directive-specific information.
serial: serial_number[-serial_number] Revokes a certificate with the specified serial number.  Serial numbers are 64-bit values, not including zero and may be expressed in decimal, hex or octal.  If two serial numbers are specified separated by a hyphen, then the range of serial numbers including and between each is revoked.  The CA key must have been specified on the ssh-keygen command line using the -s option.
id: key_id Revokes a certificate with the specified key ID string.  The CA key must have been specified on the ssh-keygen command line using the -s option.
key: public_key Revokes the specified key.  If a certificate is listed, then it is revoked as a plain public key.
sha1: public_key Revokes the specified key by including its SHA1 hash in the KRL.
sha256: public_key Revokes the specified key by including its SHA256 hash in the KRL. KRLs that revoke keys by SHA256 hash are not supported by OpenSSH versions prior to 7.9.
hash: fingerprint Revokes a key using a fingerprint hash, as obtained from a sshd(8) authentication log message or the ssh-keygen -l flag.  Only SHA256 fingerprints are supported here and resultant KRLs are not supported by OpenSSH versions prior to 7.9.
KRLs may be updated using the -u flag in addition to -k.  When this option is specified, keys listed via the command line are merged into the KRL, adding to those already there.
It is also possible, given a KRL, to test whether it revokes a particular key (or keys).  The -Q flag will query an existing KRL, testing each key specified on the command line.  If any key listed on the command line has been revoked (or an error encountered) then ssh-keygen will exit with a non-zero exit status.  A zero exit status will only be returned if no key was revoked.
When verifying signatures, ssh-keygen uses a simple list of identities and keys to determine whether a signature comes from an authorized source. This "allowed signers" file uses a format patterned after the AUTHORIZED_KEYS FILE FORMAT described in sshd(8).  Each line of the file contains the following space-separated fields: principals, options, keytype, base64-encoded key.  Empty lines and lines starting with a ‘#’ are ignored as comments.
The principals field is a pattern-list (see PATTERNS in ssh_config(5)) consisting of one or more comma-separated USER@DOMAIN identity patterns that are accepted for signing.  When verifying, the identity presented via the -I option must match a principals pattern in order for the corresponding key to be considered acceptable for verification.
The options (if present) consist of comma-separated option specifications. No spaces are permitted, except within double quotes.  The following option specifications are supported (note that option keywords are case- insensitive):
cert-authority Indicates that this key is accepted as a certificate authority (CA) and that certificates signed by this CA may be accepted for verification.
namespaces=namespace-list Specifies a pattern-list of namespaces that are accepted for this key.  If this option is present, the signature namespace embedded in the signature object and presented on the verification command- line must match the specified list before the key will be considered acceptable.
valid-after=timestamp Indicates that the key is valid for use at or after the specified timestamp, which may be a date in YYYYMMDD format or a time in YYYYMMDDHHMM[SS] format.
valid-before=timestamp Indicates that the key is valid for use at or before the specified timestamp.
When verifying signatures made by certificates, the expected principal name must match both the principals pattern in the allowed signers file and the principals embedded in the certificate itself.
An example allowed signers file:
# Comments allowed at start of line user1@example.com,user2@example.com ssh-rsa AAAAX1... # A certificate authority, trusted for all principals in a domain. *@example.com cert-authority ssh-ed25519 AAAB4... # A key that is accepted only for file signing. user2@example.com namespaces="file" ssh-ed25519 AAA41...
~/.ssh/id_dsa ~/.ssh/id_ecdsa ~/.ssh/id_ecdsa_sk ~/.ssh/id_ed25519 ~/.ssh/id_ed25519_sk ~/.ssh/id_rsa Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519, authenticator-hosted Ed25519 or RSA authentication identity of the user.  This file should not be readable by anyone but the user.  It is possible to specify a passphrase when generating the key; that passphrase will be used to encrypt the private part of this file using 128-bit AES.  This file is not automatically accessed by ssh-keygen but it is offered as the default file for the private key.  ssh(1) will read this file when a login attempt is made.
~/.ssh/id_dsa.pub ~/.ssh/id_ecdsa.pub ~/.ssh/id_ecdsa_sk.pub ~/.ssh/id_ed25519.pub ~/.ssh/id_ed25519_sk.pub ~/.ssh/id_rsa.pub Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519, authenticator-hosted Ed25519 or RSA public key for authentication. The contents of this file should be added to ~/.ssh/authorized_keys on all machines where the user wishes to log in using public key authentication.  There is no need to keep the contents of this file secret.
/etc/ssh/moduli Contains Diffie-Hellman groups used for DH-GEX.  The file format is described in moduli(5).
ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8)
The Secure Shell (SSH) Public Key File Format, RFC 4716, 2006.
is(n)                              [incr Tcl]                              is(n)
itcl::is - test argument to see if it is a class or an object
itcl::is option ?arg arg ...?
________________________________________________________________________________
The is command is used to check if the argument given is a class or an object; depending on the option given. If the argument if a class or object, then 1 is returned. Otherwise, 0 is returned.  The is command also recognizes the commands wrapped in the itcl code command.
The option argument determines what action is carried out by the command. The legal options (which may be abbreviated) are:
is class command Returns 1 if command is a class, and returns 0 otherwise.
The fully qualified name of the class needs to be given as the command argument. So, if a class resides in a namespace, then the namespace needs to be specified as well. So, if a class C resides in a namespace N, then the command should be called like:
is N::C or is ::N::C
is object ?-class className? command Returns 1 if command is an object, and returns 0 otherwise.
If the optional "-class" parameter is specified, then the command will be checked within the context of the class given. Note that className has to exist. If not, then an error will be given. So, if className is uncertain to be a class, then the programmer will need to check it's existance beforehand, or wrap it in a catch statement.
So, if c is an object in the class C, in namespace N then these are the possibilities (all return 1):
set obj [N::C c] itcl::is object N::c itcl::is object c itcl::is object $obj itcl::is object [itcl::code c]
class, object
PUPPET-AGENT(8)                   Puppet manual                  PUPPET-AGENT(8)
puppet-agent - The puppet agent daemon
Retrieves the client configuration from the Puppet master and applies it to the local host.
This service may be run as a daemon, run periodically using cron (or something similar), or run interactively for testing purposes.
puppet agent [--certname NAME] [-D|--daemonize|--no-daemonize] [-d|--debug] [--detailed-exitcodes] [--digest DIGEST] [--disable [MESSAGE]] [--enable] [--fingerprint] [-h|--help] [-l|--logdest syslog|eventlog|ABS FILEPATH|console] [--serverport PORT] [--noop] [-o|--onetime] [--sourceaddress IP_ADDRESS] [-t|--test] [-v|--verbose] [-V|--version] [-w|--waitforcert SECONDS]
This is the main puppet client. Its job is to retrieve the local machine´s configuration from a remote server and apply it. In order to successfully communicate with the remote server, the client must have a certificate signed by a certificate authority that the server trusts; the recommended method for this, at the moment, is to run a certificate authority as part of the puppet server (which is the default). The client will connect and request a signed certificate, and will continue connecting until it receives one.
Once the client has a signed certificate, it will retrieve its configuration and apply it.
´puppet agent´ does its best to find a compromise between interactive use and daemon use. If you run it with no arguments and no configuration, it goes into the background, attempts to get a signed certificate, and retrieves and applies its configuration every 30 minutes.
Some flags are meant specifically for interactive use --- in particular, ´test´, ´tags´ and ´fingerprint´ are useful.
´--test´ runs once in the foreground with verbose logging, then exits. It also exits if it can´t get a valid catalog. --test includes the ´--detailed-exitcodes´ option by default and exits with one of the following exit codes:
•   0: The run succeeded with no changes or failures; the system was already in the desired state.
•   1: The run failed, or wasn´t attempted due to another run already in progress.
•   2: The run succeeded, and some resources were changed.
•   4: The run succeeded, and some resources failed.
•   6: The run succeeded, and included both changes and failures.
´--tags´ allows you to specify what portions of a configuration you want to apply. Puppet elements are tagged with all of the class or definition names that contain them, and you can use the ´tags´ flag to specify one of these names, causing only configuration elements contained within that class or definition to be applied. This is very useful when you are testing new configurations --- for instance, if you are just starting to manage ´ntpd´, you would put all of the new elements into an ´ntpd´ class, and call puppet with ´--tags ntpd´, which would only apply that small portion of the configuration during your testing, rather than applying the whole thing.
´--fingerprint´ is a one-time flag. In this mode ´puppet agent´ runs once and displays on the console (and in the log) the current certificate (or certificate request) fingerprint. Providing the ´--digest´ option allows to use a different digest algorithm to generate the fingerprint. The main use is to verify that before signing a certificate request on the master, the certificate request the master received is the same as the one the client sent (to prevent against man-in-the-middle attacks when signing certificates).
´--skip_tags´ is a flag used to filter resources. If this is set, then only resources not tagged with the specified tags will be applied. Values must be comma-separated.
Note that any Puppet setting that´s valid in the configuration file is also a valid long argument. For example, ´server´ is a valid setting, so you can specify ´--server servername´ as an argument. Boolean settings accept a ´--no-´ prefix to turn off a behavior, translating into ´--setting´ and ´--no-setting´ pairs, such as --daemonize and --no-daemonize.
See the configuration file documentation at https://puppet.com/docs/puppet/latest/configuration.html for the full list of acceptable settings. A commented list of all settings can also be generated by running puppet agent with ´--genconfig´.
•   --certname: Set the certname (unique ID) of the client. The master reads this unique identifying string, which is usually set to the node´s fully-qualified domain name, to determine which configurations the node will receive. Use this option to debug setup problems or implement unusual node identification schemes. (This is a Puppet setting, and can go in puppet.conf.)
•   --daemonize: Send the process into the background. This is the default. (This is a Puppet setting, and can go in puppet.conf. Note the special ´no-´ prefix for boolean settings on the command line.)
•   --no-daemonize: Do not send the process into the background. (This is a Puppet setting, and can go in puppet.conf. Note the special ´no-´ prefix for boolean settings on the command line.)
•   --detailed-exitcodes: Provide extra information about the run via exit codes; works only if ´--test´ or ´--onetime´ is also specified. If enabled, ´puppet agent´ uses the following exit codes:
1: The run failed, or wasn´t attempted due to another run already in progress.
•   --digest: Change the certificate fingerprinting digest algorithm. The default is SHA256. Valid values depends on the version of OpenSSL installed, but will likely contain MD5, MD2, SHA1 and SHA256.
•   --disable: Disable working on the local system. This puts a lock file in place, causing ´puppet agent´ not to work on the system until the lock file is removed. This is useful if you are testing a configuration and do not want the central configuration to override the local state until everything is tested and committed.
Disable can also take an optional message that will be reported by the ´puppet agent´ at the next disabled run.
´puppet agent´ uses the same lock file while it is running, so no more than one ´puppet agent´ process is working at a time.
´puppet agent´ exits after executing this.
•   --enable: Enable working on the local system. This removes any lock file, causing ´puppet agent´ to start managing the local system again However, it continues to use its normal scheduling, so it might not start for another half hour.
•   --evaltrace: Logs each resource as it is being evaluated. This allows you to interactively see exactly what is being done. (This is a Puppet setting, and can go in puppet.conf. Note the special ´no-´ prefix for boolean settings on the command line.)
•   --fingerprint: Display the current certificate or certificate signing request fingerprint and then exit. Use the ´--digest´ option to change the digest algorithm used.
•   --job-id: Attach the specified job id to the catalog request and the report used for this agent run. This option only works when ´--onetime´ is used. When using Puppet Enterprise this flag should not be used as the orchestrator sets the job-id for you and it must be unique.
•   --logdest: Where to send log messages. Choose between ´syslog´ (the POSIX syslog service), ´eventlog´ (the Windows Event Log), ´console´, or the path to a log file. If debugging or verbosity is enabled, this defaults to ´console´. Otherwise, it defaults to ´syslog´ on POSIX systems and ´eventlog´ on Windows. Multiple destinations can be set using a comma separated list (eg: /path/file1,console,/path/file2)"
•   --masterport: The port on which to contact the Puppet Server. (This is a Puppet setting, and can go in puppet.conf. Deprecated in favor of the ´serverport´ setting.)
•   --noop: Use ´noop´ mode where the daemon runs in a no-op or dry-run mode. This is useful for seeing what changes Puppet would make without actually executing the changes. (This is a Puppet setting, and can go in puppet.conf. Note the special ´no-´ prefix for boolean settings on the command line.)
•   --onetime: Run the configuration once. Runs a single (normally daemonized) Puppet run. Useful for interactively running puppet agent when used in conjunction with the --no-daemonize option. (This is a Puppet setting, and can go in puppet.conf. Note the special ´no-´ prefix for boolean settings on the command line.)
•   --serverport: The port on which to contact the Puppet Server. (This is a Puppet setting, and can go in puppet.conf.)
•   --sourceaddress: Set the source IP address for transactions. This defaults to automatically selected. (This is a Puppet setting, and can go in puppet.conf.)
•   --test: Enable the most common options used for testing. These are ´onetime´, ´verbose´, ´no-daemonize´, ´no-usecacheonfailure´, ´detailed-exitcodes´, ´no-splay´, and ´show_diff´.
•   --trace Prints stack traces on some errors. (This is a Puppet setting, and can go in puppet.conf. Note the special ´no-´ prefix for boolean settings on the command line.)
•   --verbose: Turn on verbose reporting.
•   --version: Print the puppet version number and exit.
•   --waitforcert: This option only matters for daemons that do not yet have certificates and it is enabled by default, with a value of 120 (seconds). This causes ´puppet agent´ to connect to the server every 2 minutes and ask it to sign a certificate request. This is useful for the initial setup of a puppet client. You can turn off waiting for certificates by specifying a time of 0. (This is a Puppet setting, and can go in puppet.conf.)
•   --write_catalog_summary After compiling the catalog saves the resource list and classes list to the node in the state directory named classes.txt and resources.txt (This is a Puppet setting, and can go in puppet.conf.)
$ puppet agent --server puppet.domain.com
Puppet agent accepts the following signals:
SIGHUP Restart the puppet agent daemon.
SIGINT and SIGTERM Shut down the puppet agent daemon.
SIGUSR1 Immediately retrieve and apply configurations from the puppet master.
SIGUSR2 Close file descriptors for log files and reopen them. Used with logrotate.
GIT-CHERRY(1)                      Git Manual                      GIT-CHERRY(1)
git-cherry - Find commits yet to be applied to upstream
git cherry [-v] [<upstream> [<head> [<limit>]]]
Determine whether there are commits in <head>..<upstream> that are equivalent to those in the range <limit>..<head>.
The equivalence test is based on the diff, after removing whitespace and line numbers. git-cherry therefore detects when commits have been "copied" by means of git-cherry-pick(1), git-am(1) or git-rebase(1).
Outputs the SHA1 of every commit in <limit>..<head>, prefixed with - for commits that have an equivalent in <upstream>, and + for commits that do not.
-v Show the commit subjects next to the SHA1s.
<upstream> Upstream branch to search for equivalent commits. Defaults to the upstream branch of HEAD.
<head> Working branch; defaults to HEAD.
<limit> Do not report commits up to (and including) limit.
Patch workflows git-cherry is frequently used in patch-based workflows (see gitworkflows(7)) to determine if a series of patches has been applied by the upstream maintainer. In such a workflow you might create and send a topic branch like this:
$ git checkout -b topic origin/master # work and create some commits $ git format-patch origin/master $ git send-email ... 00*
Later, you can see whether your changes have been applied by saying (still on topic):
$ git fetch  # update your notion of origin/master $ git cherry -v
Concrete example In a situation where topic consisted of three commits, and the maintainer applied two of them, the situation might look like:
$ git log --graph --oneline --decorate --boundary origin/master...topic * 7654321 (origin/master) upstream tip commit [... snip some other commits ...] * cccc111 cherry-pick of C * aaaa111 cherry-pick of A [... snip a lot more that has happened ...] | * cccc000 (topic) commit C | * bbbb000 commit B | * aaaa000 commit A |/ o 1234567 branch point
In such cases, git-cherry shows a concise summary of what has yet to be applied:
$ git cherry origin/master topic - cccc000... commit C + bbbb000... commit B - aaaa000... commit A
Here, we see that the commits A and C (marked with -) can be dropped from your topic branch when you rebase it on top of origin/master, while the commit B (marked with +) still needs to be kept so that it will be sent to be applied to origin/master.
Using a limit The optional <limit> is useful in cases where your topic is based on other work that is not in upstream. Expanding on the previous example, this might look like:
$ git log --graph --oneline --decorate --boundary origin/master...topic * 7654321 (origin/master) upstream tip commit [... snip some other commits ...] * cccc111 cherry-pick of C * aaaa111 cherry-pick of A [... snip a lot more that has happened ...] | * cccc000 (topic) commit C | * bbbb000 commit B | * aaaa000 commit A | * 0000fff (base) unpublished stuff F [... snip ...] | * 0000aaa unpublished stuff A |/ o 1234567 merge-base between upstream and topic
By specifying base as the limit, you can avoid listing commits between base and topic:
$ git cherry origin/master topic base - cccc000... commit C + bbbb000... commit B - aaaa000... commit A
git-patch-id(1)
DIRCOLORS(1)                      User Commands                     DIRCOLORS(1)
dircolors - color setup for ls
dircolors [OPTION]... [FILE]
Output commands to set the LS_COLORS environment variable.
Determine format of output: -b, --sh, --bourne-shell output Bourne shell code to set LS_COLORS
-c, --csh, --c-shell output C shell code to set LS_COLORS
-p, --print-database output defaults
If FILE is specified, read it to determine which colors to use for which file types and extensions.  Otherwise, a precompiled database is used. For details on the format of these files, run 'dircolors --print-database'.
Written by H. Peter Anvin.
Full documentation <https://www.gnu.org/software/coreutils/dircolors> or available locally via: info '(coreutils) dircolors invocation'
fswatch(7)            BSD Miscellaneous Information Manual            fswatch(7)
fswatch â€” Ask for notification when the contents of the specified files or directory hierarchies are modified.
This man page is kept for reference but it is not to be considered an authoritative or complete source of information.  Please, consult the official Info documentation shipped with fswatch.
fswatch (option)* path+
The fswatch command receives notifications when the contents of the specified files or directories are modified.  fswatch implements six kind of monitors:
-       A monitor based on the File System Events API of Apple OS X.
-       A monitor based on kqueue, an event notification interface introduces in FreeBSD 4.1 and supported on most *BSD systems (including OS X).
-       A monitor based on the File Events Notification API of the Solaris kernel and its derivatives.
-       A monitor based on inotify, a Linux kernel subsystem that reports file system changes to applications.
-       A monitor based on the ReadDirectoryChangesW Microsoft Windows API.
-       A monitor which periodically stats the file system, saves file modification times in memory and manually calculates changes.
fswatch writes a record for each event it receives containing:
-       The timestamp when the event was received (optionally).
-       The path affected by the current event.
-       A space-separated list of event types (see EVENT TYPES ).
fswatch enters an infinite loop and never returns.  When it receives a SIGABRT, SIGINT or SIGTERM signal, fswatch closes the notification streams and exits gracefully returning 0 to the calling process.
-0, --print0 Use the ASCII NUL character (\0) as line separator.  Since file names can potentially contain any character but NUL, this option assures that the output of fswatch can be safely parsed using NUL as delimiter, such as using xargs -0 and the shell builtin read -d ''.
-1, --one-event Exit fswatch after the first set of events is received.
--batch-marker marker Print a marker at the end of every batch.  An optional marker marker can be specified to override its default value `NoOp'.
--event name Filter event with the specified name.  This option can be used multiple times, one for each event name that must be included in the output.
-e, --exclude regexp Exclude paths matching regexp.  Multiple exclude filters can be specified using this option multiple times.  See FILTERING PATHS for further information.