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| Newer page: | version 3 | Last edited on Monday, October 15, 2007 4:04:39 pm | by IanMcDonald | Revert |
| Older page: | version 2 | Last edited on Monday, June 3, 2002 6:50:35 pm | by perry | Revert |
@@ -1,610 +1,407 @@
-NTPD
-!!!NTPD
+<verbatim>
NAME
+ ntpd - Network Time Protocol (NTP) daemon.
+
SYNOPSIS
-DESCRIPTION
-OPTIONS
-THE CONFIGURATION FILE
-FILES
-BUGS
-AUTHOR
-----
-!!NAME
+ ntpd [ -aAbdDgLmnNqx ] [ -c conffile ] [ -f driftfile ] [ -i jaildir ]
+ [ -k keyfile ] [ -l logfile ] [ -p pidfile ] [ -P priority ] [ -r
+ broadcastdelay ] [
-s statsdir ] [
-t key ] [
-u user[:group] ] [
-v
+ variable ] [ -V variable ]
-ntpd - Network Time Protocol (NTP) daemon
.
-!!SYNOPSIS
+DESCRIPTION
+
ntpd is an operating system daemon which sets and maintains the system
+ time
-of-day in synchronism with Internet standard time servers. Ntpd
+ is a complete implementation of the
Network Time Protocol (NTP) version
+ 4 but also retains compatibility with version 3, as defined by RFC-1305
+ and version 1 and 2, as defined by RFC-1059 and RFC-1119, respectively
.
+ ntpd does most computations in 64-bit floating point arithmetic and
+ does relatively clumsy 64-bit fixed point operations only when neces‐
+ sary to preserve the ultimate precision, about 232 picoseconds. While
+ the ultimate precision, is not achievable with ordinary workstations
+ and networks of today, it may be required with future nanosecond CPU
+ clocks and gigabit LANs.
+ The daemon can operate in any of several modes, including symmetric
+ active/passive, client/server broadcast/multicast and manycast. A
+ broadcast/multicast or manycast client can discover remote servers,
+ compute server-client propagation delay correction factors and config‐
+ ure itself automatically. This makes it possible to deploy a fleet of
+ workstations without specifying configuration details specific to the
+ local environment.
-__
ntpd__ [[ -aAbdm ] [[ -c conffile ] [[ -f driftfile ] [[ -k
-keyfile ] [[ -l logfile ] [[ -p pidfile ] [[ -r broadcastdelay
-] [[ -s statsdir ] [[ -t key ] [[ -v variable ] [[ -V variable
-]
-!!DESCRIPTION
+ Ordinarily,
ntpd reads the ntp.conf configuration file at startup time
+ in order to determine the synchronization sources and operating modes.
+ It is also possible to specify a working, although limited configura‐
+ tion entirely on the command line, obviating the need for a configura‐
+ tion file. This may be particularly appropriate when the local host is
+ to be configured as a broadcast/multicast client or manycast client,
+ with all peers being determined by listening to broadcasts at run time.
+ If NetInfo support is built into ntpd then ntpd will attempt to read
+ its configuration from the NetInfo if the default ntp.conf file cannot
+ be read and no file is specified by the -c option.
-__
ntpd__ is an operating system daemon which sets
and
-maintains
the system time-of-day in synchronism with
-Internet standard time servers. __Ntpd__
is a complete
-implementation of
the Network Time Protocol (NTP) version 4
-but also retains compatibility with version 3, as defined by
-RFC-1305
and version 1 and 2, as defined by RFC-1059 and
-RFC-1119, respectively. __
ntpd__ does most computations
-in 64-bit floating point arithmetic and does relatively
-clumsy 64-bit fixed point operations only when necessary to
-preserve the ultimate precision, about 232 picoseconds.
-While the ultimate precision, is not achievable with
-ordinary workstations and networks of today, it may be
-required with future nanosecond CPU clocks and gigabit
-LANs
.
+ Various internal
ntpd variables can be displayed
and configuration
+ options altered while
the daemon
is running using
the ntpq
and
ntpd
+ utility programs
.
+ When ntpd starts it looks at the value of umask, and if it is zero ntpd
+ will set the umask to 0222.
-The daemon can operate in any of several modes, including
-symmetric active/passive, client/server broadcast/multicast
-and manycast. A broadcast/multicast or manycast client can
-discover remote servers, compute server
-client propagation
-delay correction factors and configure itself automatically.
-This makes it possible to deploy
a fleet of workstations
-without specifying configuration details specific to the
-local environment
.
+OPTIONS
+
-a Enable authentication mode (default)
.
+ -A Disable authentication mode.
-Ordinarily, __ntpd__ reads the ntp.conf configuration
-file at startup time in order to determine the
-synchronization sources and operating modes. It is also
-possible to specify a working, although limited
-configuration entirely on the command line, obviating the
-need for a configuration file. This may be particularly
-appropriate when the local host is to be configured as a
-/multicast client or manycast client, with all
-peers being determined by listening to broadcasts at run
-time
.
+ -b Synchronize using NTP
broadcast messages
.
+ -c conffile
+ Specify the name and path of the configuration file.
-If !NetInfo support is built into __ntpd__ then
-__ntpd__ will attempt to read its configuration from the
-!NetInfo if the default ntp
.conf file cannot be read and no
-file is specified by the -c option
.
+ -d Specify debugging mode
. This flag may occur multiple times,
+ with each occurrence indicating greater detail of display
.
+ -D level
+ Specify debugging level directly.
-Various internal __ntpd__ variables can be displayed and
-configuration options altered while
the daemon is running
-using
the __ntpq__ and __ntpd__ utility
-programs
.
+ -f driftfile
+ Specify
the name and path of
the drift file
.
+ -g Normally, the daemon exits if the offset exceeds a 1000s sanity
+ limit. This option overrides this limit and allows the time to
+ be set to an value without restriction.
-When __ntpd__ starts it looks at
the value of umask
, and
-if
it is zero __ntpd__ will set
the umask
to
-0222
.
-!!OPTIONS
+ -i jaildir
+ Chroot
the server to the directory jaildir. This option also
+ implies that the server attempts to drop root privileges at
+ startup (otherwise
, chroot gives very little additional secu‐
+ rity), and
it is only available if
the OS supports
to run the
+ server without full root privileges
. You may need to also spec‐
+ ify a -u option.
+ -k keyfile
+ Specify the name and path of the file containing the NTP authen‐
+ tication keys.
-''
-a''
+
-l logfile
+ Specify the name and path of the log file. The default is the
+ system log facility.
+ -L Do not listen to virtual IPs. The default is to listen.
-Enable authentication mode
(default
). ''-A''
+ -m Synchronize using NTP multicast messages on the IP multicast
+ group address 224..1.1
(requires multicast kernel
).
+ -n Don’t fork, i.e. run in the foreground.
-Disable authentication mode
.
+ -N To the extent permitted by the operating system, run the ntpd at
+ the highest priority
.
+ -p pidfile
+ Specify the name and path to record the daemon’s process ID.
-''
-b''
+
-P Override the priority limit set by the operating system. Not
+ recommended for sissies.
+ -q Exit the ntpd just after the first time the clock is set. This
+ behavior mimics that of the ntpdate program, which is to be
+ retired. The -g and -x options can be used with this option.
+ Note: The kernel time discipline is disabled with this option.
-Synchronize using NTP
broadcast messages
.
+ -r broadcastdelay
+ Specify the default propagation delay from the
broadcast/multi‐
+ cast server and this computer. This is necessary only if the
+ delay cannot be computed automatically by the protocol
.
+ -s statsdir
+ Specify the directory path for files created by the statistics
+ facility.
-''
-c conffile''
+
-t key Add a key number to the trusted key list.
+ -u user[:group]
+ Specify a user, and optionally a group, to switch to.
-Specify the name and path of the configuration
-file.
+ -v variable
+ -V variable
+ Add a system variable listed by default.
-''
-d''
+
-x Ordinarily, if the time is to be adjusted more than 128 ms, it
+ is stepped, not gradually slewed. This option forces the time
+ to be slewed in all cases. Note: Since the slew rate is limited
+ to .5 ms/s, each second of adjustment requires an amortization
+ interval of 2000 s. Thus an adjustment of many seconds can take
+ hours or days to amortize.
+THE CONFIGURATION FILE
+ The ntpd configuration file is read at initial startup in order to
+ specify the synchronization sources, modes and other related informa‐
+ tion. Usually, it is installed in the /etc directory, but could be
+ installed elsewhere (see the -c conffile command line option). The
+ file format is similar to other Unix configuration files - comments
+ begin with a # character and extend to the end of the line; blank lines
+ are ignored. Configuration commands consist of an initial keyword fol‐
+ lowed by a list of arguments, some of which may be optionally separated
+ by whitespace. Commands may not be continued over multiple lines.
+ Arguments may be host names, host addresses written in numeric dotted-
+ quad form, integers, floating point numbers (when specifying times in
+ seconds) and text strings. Optional arguments are delimited by [ ] in
+ the following descriptions, while alternatives are separated by |. The
+ notation [ ... ] means an optional, indefinite repetition of the last
+ item before the [ ... ].
-Specify debugging mode. This flag may occur multiple times
,
-with each occurrence indicating greater detail
of
-display
.
+ While there is a rich set of options available
, the only required
+ option is one or more
of the server, peer, broadcast or manycastclient
+ commands
.
+ Following is a description of the NTPv4 configuration commands. These
+ commands have the same basic functions as in NTPv3 and in some cases
+ new functions and new operands. The various modes are determined by
+ the command keyword and the type of the required IP address. Addresses
+ are classed by type as (s) a remote server or peer (IP class A, B and
+ C), (b) the broadcast address of a local interface, (m) a multicast
+ address (IP class D), or (r) a reference clock address (127.127.x.x).
+ Note that, while autokey and burst modes are supported by these com‐
+ mands, their effect in some weird mode combinations can be meaningless
+ or even destructive.
-''-D level''
+ peer address
+ [autokey | key key] [burst] [version version] [prefer] [minpoll
+ minpoll] [maxpoll maxpoll]
+ For type s addresses (only), this operates as the current peer command
+ which mobilizes a persistent symmetric-active mode association, except
+ that additional modes are available. This command should NOT be used
+ for type b, m or r addresses.
-Specify debugging level directly
.
+ The peer command specifies that the local server is to operate in sym‐
+ metric active mode with the remote server. In this mode, the local
+ server can be synchronized to the remote server and, in addition, the
+ remote server can be synchronized by the local server. This is useful
+ in a network of servers where, depending on various failure scenarios
+ either the local or remote server may be the better source of time
.
+ server address
+ [autokey | key key] [burst] [version version] [prefer] [minpoll
+ minpoll] [maxpoll maxpoll]
-''-f driftfile''
+ For type s and r addresses, this operates as the NTPv3 server command
+ which mobilizes a persistent client mode association. The server com‐
+ mand specifies that the local server is to operate in client mode with
+ the specified remote server. In this mode, the local server can be
+ synchronized to the remote server, but the remote server can never be
+ synchronized to the local server.
+ broadcast address
+ [autokey | key key] [burst] [version version] [minpoll minpoll]
+ [maxpoll maxpoll] [ttl ttl]
-Specify
the name
and path of
the drift file
.
+ For type b and m addresses (only), this operates as
the current NTPv3
+ broadcast command, which mobilizes a persistent broadcast mode associa‐
+ tion, except that additional modes are available. Multiple commands
+ can be used to specify multiple local broadcast interface (subnets)
+
and/or multiple multicast groups. Note that local broadcast messages
+ go only to the interface associated with the subnet specified but mul‐
+ ticast messages go to all interfaces. In the current implementation,
+ the source address used for these messages is
the Unix host default
+ address
.
+ In broadcast mode, the local server sends periodic broadcast messages
+ to a client population at the address specified, which is usually the
+ broadcast address on (one of) the local network(s) or a multicast
+ address assigned to NTP. The IANA has assigned the multicast group
+ address 224.0.1.1 exclusively to NTP, but other nonconflicting
+ addresses can be used to contain the messages within administrative
+ boundaries. Ordinarily, this specification applies only to the local
+ server operating as a sender; for operation as a broadcast client, see
+ the broadcastclient or multicastclient commands below.
-''-g''
+ manycastclient address
+ [autokey | key key] [burst] [version version] [minpoll minpoll]
+ [maxpoll maxpoll] [ttl ttl]
+ For type m addresses (only), this mobilizes a manycast client-mod asso‐
+ ciation for the multicast address specified. In this case specific
+ address must be supplied which matches the address used on th manycast‐
+ server command for the designated manycast servers. The NT multicast
+ address 224.0.1.1 assigned by the IANA should NOT be used unless spe‐
+ cific means are taken to avoid spraying large areas of th Internet with
+ these messages and causing a possibly massive implosion o replies at
+ the sender
-Normally,
the daemon exits if
the offset exceeds
a 1000s
-sanity limit This option overrides this limit and allows
the
-time
to be set to an value without restriction
.
+ The manycast command specifies that
the local server is to operate i
+ client mode with
the remote server that are discovered as the result o
+ broadcast/multicast messages. The client broadcasts
a request message
+ to
the group address associated with the specified address an specifi‐
+ cally enabled servers respond
to these messages
. The client selects
+ the servers providing the best time and continues as with the server
+ command. The remaining servers are discarded as if never heard
+ These four commands specify the time server name or address to be use
+ and the mode in which to operate. The address can be either a DNS name
+ or a IP address in dotted-quad notation. Additional information on
+ association behaviour can be found in the Association Management page
-''-k keyfile''
+ autokey
+ All packets sent to the address are to include authentication
+ field encrypted using the autokey scheme.
+ burst At each poll interval, send a burst of eight packets spaced,
+ instead of the usual one.
-Specify
the name and path of
the file containing the NTP
-authentication keys
.
+ key key
+ All packets sent to
the address are to include authentication
+ field encrypted using
the specified key identifier, which is an
+ unsigned 32-bit integer less than 65536. The default is to
+ include no encryption field
.
+ version version
+ Specifies the version number to be used for outgoing NTP pack‐
+ ets. Versions 1-4 are the choices, with version 4 the default.
-''-l logfile''
+ prefer Marks the server as preferred. All other things being equal,
+ this host will be chosen for synchronization among a set of cor‐
+ rectly operating hosts. See the Mitigation Rules and the prefer
+ Keyword page for further information
+ ttl ttl
+ This option is used only with broadcast mode. It specifies the
+ time-to-live ttl to use on multicast packets. Selection of the
+ proper value, which defaults to 127, is something of a black art
+ and must be coordinated with the network administrator.
-Specify
the name
and path of the log file
. The default is
-the system log facility
.
+ minpoll minpoll maxpoll maxpoll
+ These options specify
the minimum
and maximum polling intervals
+ for NTP messages. The values are interpreted as dual logarithms
+ (2 ^ x)
. The default range
is 6 (2^6 = 64 s) to 10 (2^10 = 1024
+ s). The allowable range is 4 (16 s) to 17 (36.4 h)
.
+ broadcastclient
+ This command directs the local server to listen for and respond
+ to broadcast messages received on any local interface. Upon
+ hearing a broadcast message for the first time, the local server
+ measures the nominal network delay using a brief client/server
+ exchange with the remote server, then enters the broadcastclient
+ mode, in which it listens for and synchronizes to succeeding
+ broadcast messages. Note that, in order to avoid accidental or
+ malicious disruption in this mode, both the local and remote
+ servers should operate using authentication and the same trusted
+ key and key identifiers.
-''-m''
+ multicastclient
+ [address] [...] This command directs the local server to listen
+ for multicast messages at the group address(es) of these global
+ network. The default address is that assigned by the Number
+ Czar to NTP (224..1.1). This command operates in the same way
+ as the broadcastclient command, but uses IP multicasting. Sup‐
+ port for this command requires a multicast kernel.
+ driftfile driftfile
+ This command specifies the name of the file use to record the
+ frequency offset of the local clock oscillator. If the file
+ exists, it is read at startup in order to set the initial fre‐
+ quency offset and then updated once per hour with the current
+ frequency offset computed by the daemon. If the file does not
+ exist or this command is not given, the initial frequency offset
+ is assume zero. In this case, it may take some hours for the
+ frequency to stabilize and the residual timing errors to sub‐
+ side.
-Synchronize using NTP multicast messages on
the IP multicast
-group address 224
.1.1 (requires multicast
-kernel)
.
+ The file format consists of a single line containing a single floating
+ point number, which records
the frequency offset measured in parts-per-
+ million (PPM)
. The file is updated by first writing the current drift
+ value into a temporary file and then renaming this file to replace the
+ old version
. This implies that ntpd must have write permission for the
+ directory the drift file is located in, and that file system links,
+ symbolic or otherwise, should be avoided
.
+ manycastserver address [...]
+ This command directs the local server to listen for and respond
+ to broadcast messages received on any local interface, and in
+ addition enables the server to respond to client mode messages
+ to the multicast group address(es) (type m) specified. At least
+ one address is required, but the NTP multicast address 224.0.1.1
+ assigned by the IANA should NOT be used, unless specific means
+ are taken to limit the span of the reply and avoid a possible
+ massive implosion at the original sender.
-''
-p pidfile''
+ revoke [logsec]
+ Specifies the interval between recomputations of the private
+ value used with the autokey feature, which ordinarily requires
+ an expensive public
- key computation. The default value is 12
+ (65,536 s or about 18 hours). For poll intervals above the
+ specified interval, a new private value will be recomputed for
+ every message sent.
+ autokey [logsec]
+ Specifies the interval between regenerations of the session key
+ list used with the autokey feature. Note that the size of the
+ key list for each association depends on this interval and the
+ current poll interval. The default value is 12 (4096 s or about
+ 1.1 hours). For poll intervals above the specified interval, a
+ session key list with a single entry will be regenerated for
+ every message sent.
-Specify the name and path to record the daemon's process
-ID.
+ enable [auth | bclient | kernel | monitor | ntp | stats]
+ disable [auth | bclient | kernel | monitor | ntp | stats]
+ Provides a way to enable or disable various server options.
+ Flags not mentioned are unaffected. Note that all of these
+ flags can be controlled remotely using the ntpdc utility pro‐
+ gram.
-''-P''
+ auth Enables the server to synchronize with unconfigured peers only
+ if the peer has been correctly authenticated using a trusted key
+ and key identifier. The default for this flag is enable.
+ bclient
+ When enabled, this is identical to the broadcastclient command.
+ The default for this flag is disable.
-Override
the priority limit set by
the operating
system. Not
-recommended
for sissies
.
+ kernel Enables
the precision-time kernel support for
the ntp_adjtime()
+
system call, if implemented
. Ordinarily, support for this rou‐
+ tine is detected automatically when the NTP daemon is compiled,
+ so it is not necessary
for the user to worry about this flag.
+ It flag is provided primarily so that this support can be dis‐
+ abled during kernel development
.
+ monitor
+ Enables the monitoring facility. See the ntpdc program and the
+ monlist command or further information. The default for this
+ flag is enable.
-''
-r broadcastdelay''
+ ntp Enables the server to adjust its local clock by means of NTP.
+ If disabled, the local clock free
-runs at its intrinsic time and
+ frequency offset. This flag is useful in case the local clock
+ is controlled by some other device or protocol and NTP is used
+ only to provide synchronization to other clients In this case,
+ the local clock driver can be used to provide this function and
+ also certain time variables for error estimates and leap-indica‐
+ tors. The default for this flag is enable.
+ stats Enables the statistics facility. The default for this flag is
+ enable.
-Specify the default propagation delay from the
-broadcast
/multicast server and this computer
. This is
-necessary only if
the delay cannot be computed automatically
-by
the protocol.
+FILES
+
/etc/ntp
.conf
+ -
the default name of
the configuration file
+ /etc/ntp.drift
+ - the default name of the drift file
-''
-s statsdir''
+ /etc/ntp.key
+
- the default name of the key file
+BUGS
+ Ntpd has gotten rather fat. While not huge, it has gotten larger than
+ might be desirable for an elevated-priority daemon running on a work‐
+ station, particularly since many of the fancy features which consume
+ the space were designed more with a busy primary server, rather than a
+ high stratum workstation, in mind.
-Specify the directory path for files created by the
-statistics facility
.
-
-
-''-t key''
-
-
-Add a key number to the trusted key list
. ''-v
-variable''
-
-
-''-V variable''
-
-
-Add a system variable listed by default
.
-
-
-''-x''
-
-
-Ordinarily, if
the time is to be adjusted more than 128 ms,
-it is stepped, not gradually slewed. This option forces the
-time to be slewed in all cases. Note: Since the slew rate is
-limited to .5 ms/s, each second of adjustment requires an
-amortization interval of 2000 s. Thus an adjustment of many
-seconds can take hours or days to amortize.
-!!THE CONFIGURATION FILE
-
-
-The __ntpd__ configuration file is read at initial
-startup in order to specify the synchronization sources,
-modes and other related information. Usually, it is
-installed in the /etc directory, but could be installed
-elsewhere (see the -c conffile command line option). The
-file format is similar to other Unix configuration files -
-comments begin with a # character and extend to the end of
-the line; blank lines are ignored. Configuration commands
-consist of an initial keyword followed
by a list of
-arguments, some of which may be optionally separated by
-whitespace. Commands may not be continued over multiple
-lines. Arguments may be host names, host addresses written
-in numeric dotted-quad form, integers, floating point
-numbers (when specifying times in seconds) and text strings.
-Optional arguments are delimited by [[ ] in the following
-descriptions, while alternatives are separated by |. The
-notation [[ ... ] means an optional, indefinite repetition of
-the last item before the [[ ... ].
-
-
-While there is a rich set of options available, the only
-required option is one or more of the server, peer,
-broadcast or manycastclient commands.
-
-
-Following is a description of the NTPv4 configuration
-commands. These commands have the same basic functions as in
-NTPv3 and in some cases new functions and new operands. The
-various modes are determined by the command keyword and the
-type of the required IP address. Addresses are classed by
-type as (s) a remote server or peer (IP class A, B and C),
-(b) the broadcast address of a local interface, (m) a
-multicast address (IP class D), or (r) a reference clock
-address (127.127.x.x). Note that, while autokey and burst
-modes are supported by these commands, their effect in some
-weird mode combinations can be meaningless or even
-destructive.
-
-
-''peer address''
-
-
-[[autokey | key key] [[burst] [[version version] [[prefer]
-[[minpoll minpoll] [[maxpoll maxpoll]
-
-
-For type s addresses (only), this operates as the current
-peer command which mobilizes a persistent symmetric-active
-mode association, except that additional modes are
-available. This command should NOT be used for type b, m or
-r addresses.
-
-
-The peer command specifies that the local server is to
-operate in symmetric active mode with the remote server. In
-this mode, the local server can be synchronized to the
-remote server and, in addition, the remote server can be
-synchronized by the local server. This is useful in a
-network of servers where, depending on various failure
-scenarios either the local or remote server may be the
-better source of time.
-
-
-''server address''
-
-
-[[autokey | key key] [[burst] [[version version] [[prefer]
-[[minpoll minpoll] [[maxpoll maxpoll]
-
-
-For type s and r addresses, this operates as the NTPv3
-server command which mobilizes a persistent client mode
-association. The server command specifies that the local
-server is to operate in client mode with the specified
-remote server. In this mode, the local server can be
-synchronized to the remote server, but the remote server can
-never be synchronized to the local server.
-
-
-''broadcast address''
-
-
-[[autokey | key key] [[burst] [[version version] [[minpoll
-minpoll] [[maxpoll maxpoll] [[ttl ttl]
-
-
-For type b and m addresses (only), this operates as the
-current NTPv3 broadcast command, which mobilizes a
-persistent broadcast mode association, except that
-additional modes are available. Multiple commands can be
-used to specify multiple local broadcast interface (subnets)
-and/or multiple multicast groups. Note that local broadcast
-messages go only to the interface associated with the subnet
-specified but multicast messages go to all interfaces. In
-the current implementation, the source address used for
-these messages is the Unix host default
-address.
-
-
-In broadcast mode, the local server sends periodic broadcast
-messages to a client population at the address specified,
-which is usually the broadcast address on (one of) the local
-network(s) or a multicast address assigned to NTP. The IANA
-has assigned the multicast group address 224..1.1
-exclusively to NTP, but other nonconflicting addresses can
-be used to contain the messages within administrative
-boundaries. Ordinarily, this specification applies only to
-the local server operating as a sender; for operation as a
-broadcast client, see the broadcastclient or multicastclient
-commands below.
-
-
-''manycastclient address''
-
-
-[[autokey | key key] [[burst] [[version version] [[minpoll
-minpoll] [[maxpoll maxpoll] [[ttl ttl]
-
-
-For type m addresses (only), this mobilizes a manycast
-client-mod association for the multicast address specified.
-In this case specific address must be supplied which matches
-the address used on th manycastserver command for the
-designated manycast servers. The NT multicast address
-224..1.1 assigned by the IANA should NOT be used unless
-specific means are taken to avoid spraying large areas of th
-Internet with these messages and causing a possibly massive
-implosion o replies at the sender
-
-
-The manycast command specifies that the local server is to
-operate i client mode with the remote server that are
-discovered as the result o broadcast/multicast messages. The
-client broadcasts a request message to the group address
-associated with the specified address an specifically
-enabled servers respond to these messages. The client
-selects the servers providing the best time and continues as
-with the server command. The remaining servers are discarded
-as if never heard
-
-
-These four commands specify the time server name or address
-to be use and the mode in which to operate. The address can
-be either a DNS name or a IP address in dotted-quad
-notation. Additional information on association behaviour
-can be found in the Association Management page
-
-
-''autokey''
-
-
-All packets sent to the address are to include
-authentication field encrypted using the autokey
-scheme.
-
-
-''burst''
-
-
-At each poll interval, send a burst of eight packets spaced,
-instead of the usual one.
-
-
-''key key''
-
-
-All packets sent to the address are to include
-authentication field encrypted using the specified key
-identifier, which is an unsigned 32-bit integer less than
-65536. The default is to include no encryption
-field.
-
-
-''version version''
-
-
-Specifies the version number to be used for outgoing NTP
-packets. Versions 1-4 are the choices, with version 4 the
-default.
-
-
-''prefer''
-
-
-Marks the server as preferred. All other things being equal,
-this host will be chosen for synchronization among a set of
-correctly operating hosts. See the Mitigation Rules and the
-prefer Keyword page for further information
-
-
-''ttl ttl''
-
-
-This option is used only with broadcast mode. It specifies
-the time-to-live ttl to use on multicast packets. Selection
-of the proper value, which defaults to 127, is something of
-a black art and must be coordinated with the network
-administrator.
-
-
-''minpoll minpoll maxpoll maxpoll''
-
-
-These options specify the minimum and maximum polling
-intervals for NTP messages, in seconds to the power of two.
-The default range is 6 (64 s) to 10 (1,024 s).The allowable
-range is 4 (16 s) to 17 (36.4 h) inclusive.
-
-
-''broadcastclient''
-
-
-This command directs the local server to listen for and
-respond to broadcast messages received on any local
-interface. Upon hearing a broadcast message for the first
-time, the local server measures the nominal network delay
-using a brief client/server exchange with the remote server,
-then enters the broadcastclient mode, in which
it listens
-for and synchronizes to succeeding broadcast messages
. Note
-that, in order to avoid accidental or malicious disruption
-in this mode, both the local and remote servers should
-operate using authentication and the same trusted key and
-key identifiers
.
-
-
-''multicastclient''
-
-
-[[address] [[...] This command directs the local server to
-listen for multicast messages at the group address(
es) of
-these global network
. The default address is that assigned
-by the Number Czar to NTP (224..1.1). This command operates
-in the same way as the broadcastclient command, but uses IP
-multicasting. Support for this command requires a multicast
-kernel.
-
-
-''driftfile driftfile''
-
-
-This command specifies the name of the file use to record
-the frequency offset of the local clock oscillator. If the
-file exists, it is read at startup in order to set the
-initial frequency offset and then updated once per hour with
-the current frequency offset computed by the daemon. If the
-file does not exist or this command is not given, the
-initial frequency offset is assume zero. In this case, it
-may take some hours for the frequency to stabilize and the
-residual timing errors to subside.
-
-
-The file format consists of a single line containing a
-single floating point number, which records the frequency
-offset measured in parts-per-million (PPM). The file is
-updated by first writing the current drift value into a
-temporary file and then renaming this file to replace the
-old version. This implies that ntpd must have write
-permission for the directory the drift file is located in,
-and that file system links, symbolic or otherwise, should be
-avoided.
-
-
-''manycastserver address [[...]''
-
-
-This command directs the local server to listen for and
-respond to broadcast messages received on any local
-interface, and in addition enables the server to respond to
-client mode messages to the multicast group address(es)
-(type m) specified. At least one address is required, but
-the NTP multicast address 224..1.1 assigned by the IANA
-should NOT be used, unless specific means are taken to limit
-the span of the reply and avoid a possible massive implosion
-at the original sender.
-
-
-''revoke [[logsec]''
-
-
-Specifies the interval between recomputations of the private
-value used with the autokey feature, which ordinarily
-requires an expensive public- key computation. The default
-value is 12 (65,536 s or about 18 hours). For poll intervals
-above the specified interval, a new private value will be
-recomputed for every message sent.
-
-
-''autokey [[logsec]''
-
-
-Specifies the interval between regenerations of the session
-key list used with the autokey feature. Note that the size
-of the key list for each association depends on this
-interval and the current poll interval. The default value is
-12 (4096 s or about 1.1 hours). For poll intervals above the
-specified interval, a session key list with a single entry
-will be regenerated for every message sent.
-
-
-''enable [[auth | bclient | kernel | monitor | ntp |
-stats]''
-
-
-''disable [[auth | bclient | kernel | monitor | ntp |
-stats]''
-
-
-Provides a way to enable or disable various server options.
-Flags not mentioned are unaffected. Note that all of these
-flags can be controlled remotely using the ntpdc utility
-program.
-
-
-''auth''
-
-
-Enables the server to synchronize with unconfigured peers
-only if the peer has been correctly authenticated using a
-trusted key and key identifier. The default for this flag is
-enable.
-
-
-''bclient''
-
-
-When enabled, this is identical to the broadcastclient
-command. The default for this flag is disable.
-
-
-''kernel''
-
-
-Enables the precision-time kernel support for the
-ntp_adjtime() system call, if implemented. Ordinarily,
-support for this routine is detected automatically when the
-NTP daemon is compiled, so it is not necessary for the user
-to worry about this flag. It flag is provided primarily so
-that this support can be disabled during kernel
-development.
-
-
-''monitor''
-
-
-Enables the monitoring facility. See the ntpdc program and
-the monlist command or further information. The default for
-this flag is enable.
-
-
-''ntp''
-
-
-Enables the server to adjust its local clock by means of
-NTP. If disabled, the local clock free-runs at its intrinsic
-time and frequency offset. This flag is useful in case the
-local clock is controlled by some other device or protocol
-and NTP is used only to provide synchronization to other
-clients In this case, the local clock driver can be used to
-provide this function and also certain time variables for
-error estimates and leap-indicators. The default for this
-flag is enable.
-
-
-''stats''
-
-
-Enables the statistics facility. The default for this flag
-is enable.
-!!FILES
-
-
-''
/etc/ntp.conf''
-
-
-- the default name of the configuration file
-
-
-''/etc/ntp.drift''
-
-
-- the default name of the drift file
-
-
-''/etc/ntp.key''
-
-
-- the default name of the key file
-!!BUGS
-
-
-__Ntpd__ has gotten rather fat. While not huge, it has
-gotten larger than might be desirable for an
-elevated-priority daemon running on a workstation,
-particularly since many of the fancy features which consume
-the space were designed more with a busy primary server,
-rather than a high stratum workstation, in
-mind.
-!!AUTHOR
-
-
-David L. Mills
-----
+AUTHOR
+ David L
. Mills <mills@udel
.edu>
. Manpage abstracted from
the html doc‐
+ umentation
by Peter Breuer <ptb@
it.uc3m
.es>
.
+<
/verbatim>
