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`ntpd` 是否设置硬件时钟？

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`ntpd` 是否设置硬件时钟？

是否ntpd设置硬件时钟？

如果我通过选项，是否ntpd设置硬件时钟-q（意味着一次性校正）？

Linux 3.5.6、ntp 4.2.6.p5。

这里据说 ntpd 每 11 分钟将系统时钟同步到硬件，但我在 ntpd mans 中找不到对此的参考。

答案1

类似的问题被问到服务器故障网。这就是答案。

来自hwclockRHEL 4.6 的手册页：

This mode (we'll call it "11 minute mode") is off until something turns it on.  The ntp
daemon  xntpd  is  one thing  that  turns  it on.  You can turn it off by running
anything, including hwclock --hctosys, that sets the System Time the old fashioned way.

To see if it is on or off, use the command adjtimex --print and look at the value of
"status".  If the "64" bit of this number (expressed in binary) equal to 0, 11 minute mode 
is on.  Otherwise, it is off.

所以，由于你跑步，hwclock --set你很可能已经把它关掉了。同样的道理，你可以检查输出来adjtimex --print确认。

答案2

亲自查看（以下脚本近乎实时地显示当前“时间状态”，同时记录值的突然变化）

#!/bin/sh
set -eu

get_time() {
    local line="$1"
    timedatectl \
        | sed -nE $line'p' \
        | sed -E 's/.* ([0-9]+):([0-9]+):([0-9]+).*/\1\2\3/'
}


get_time_status() {
    adjtimex --print \
        | grep -F status \
        | awk '{print "obase=2;" $2}' \
        | bc
}


num_diff() {
    local a="$1" b="$2"
    echo "ah = ${a:0:2}; am = ${a:2:2}; as = ${a:4:2}
        bh = ${b:0:2}; bm = ${b:2:2}; bs = ${b:4:2}
        a = ah * 60 * 60 + am * 60 + as
        b = bh * 60 * 60 + bm * 60 + bs
        if (a > b) a - b else b - a" | bc
}


print_line() {
    local f1="$1" f2="$2"
    printf "%20s %-$(($(tput cols) - 21))s\n" "$f1" "$f2"
}


localt=
universalt=
rtct=
ntp_enabled=
ntp_synchronized=
time_status=

localt_prv="$(get_time 1)"
universalt_prv="$(get_time 2)"
rtct_prv="$(get_time 3)"
ntp_enabled_prv="$(timedatectl | grep -E 'NTP enabled' | awk '{print $3}')"
ntp_synchronized_prv="$(timedatectl | grep -E 'NTP synchronized' | awk '{print $3}')"
time_status_prv="$(get_time_status)"

while true; do
    localt="$(get_time 1)"
    universalt="$(get_time 2)"
    rtct="$(get_time 3)"
    ntp_enabled="$(timedatectl | grep -E 'NTP enabled' | awk '{print $3}')"
    ntp_synchronized="$(timedatectl | grep -E 'NTP synchronized' | awk '{print $3}')"
    time_status="$(get_time_status)"

    if [ "$(num_diff $localt $localt_prv)" -gt 5 ]; then
        print_line "[$(date +%H:%M:%S)]" "localt: $localt_prv -> $localt"
    fi
    if [ "$(num_diff $universalt $universalt_prv)" -gt 5 ]; then
        print_line "[$(date +%H:%M:%S)]" "universalt: $universalt_prv -> $universalt"
    fi
    if [ "$(num_diff $rtct $rtct_prv)" -gt 5 ]; then
        print_line "[$(date +%H:%M:%S)]" "rtct: $rtct_prv -> $rtct"
    fi
    if [ "$ntp_enabled" != "$ntp_enabled_prv" ]; then
        print_line "[$(date +%H:%M:%S)]" "ntp_enabled: $ntp_enabled_prv -> $ntp_enabled"
    fi
    if [ "$ntp_synchronized" != "$ntp_synchronized_prv" ]; then
        print_line "[$(date +%H:%M:%S)]" "ntp_synchronized: $ntp_synchronized_prv -> $ntp_synchronized"
    fi
    if [ "$time_status" != "$time_status_prv" ]; then
        print_line "[$(date +%H:%M:%S)]" "time_status: $time_status_prv -> $time_status"
    fi

    print_line local: "$localt"
    print_line universal: "$universalt"
    print_line rtc: "$rtct"
    print_line 'NTP enabled:' "$ntp_enabled"
    print_line 'NTP synchronized:' "$ntp_synchronized"
    print_line 'time status:' "$time_status"

    sleep 1

    localt_prv="$localt"
    universalt_prv="$universalt"
    rtct_prv="$rtct"
    ntp_enabled_prv="$ntp_enabled"
    ntp_synchronized_prv="$ntp_synchronized"
    time_status_prv="$time_status"

    printf '\033[6A'
done

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