# uptime -s
2020-10-31 15:24:21
# head -1 /var/log/syslog
Oct 31 15:50:53 ...
观察:正常运行时间早于系统日志中的第一个时间戳
DHCP IP 已于 15:51 获取
Oct 31 15:51:34 dhclient[841]: DHCPOFFER of 10.50.51.49 from 10.50.51.102
Oct 31 15:51:38 dhclient[841]: bound to 10.50.51.49 -- renewal in 145 seconds
NTP 同步启动,时间回溯至 15:25(回溯约 25 分钟)
Oct 31 15:52:03 ntpd[944]: ...
Oct 31 15:25:42 ntpd[944]: ntpd: time set -1588.158001 s
NTP 似乎也因时间设置而删除了接口
Oct 31 15:30:09 ntpd[1278]: Deleting interface #3 eth0, 10.50.51.49#123, interface stats: received=27, sent=27, dropped=0, active_time=226 secs
下次更新时间为 15:54
Oct 31 15:54:03 dhclient[841]: DHCPREQUEST for 10.50.51.49 on eth0 to 10.50.51.102
由于 NTP,DHCP 更新不会在约 145 秒内发生,而是在 25 分钟内发生
我在 ubuntu 20.04 上安装了以下软件包:
# dpkg -l | grep dhc
ii isc-dhcp-client 4.4.1-2.1ubuntu5 amd64 DHCP client for automatically obtaining an IP address
# dpkg -l | grep bind
ii bind9-dnsutils 1:9.16.1-0ubuntu2.4 amd64 Clients provided with BIND 9
ii bind9-host 1:9.16.1-0ubuntu2.4 amd64 DNS Lookup Utility
ii bind9-libs:amd64 1:9.16.1-0ubuntu2.4 amd64 Shared Libraries used by BIND 9
DHCP 进程正在运行:
root 841 0.0 0.2 99896 5960 ? Ssl Oct31 0:00 /sbin/dhclient -1 -4 -v -i -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -I -df /var/lib/dhcp/dhclient6.eth0.leases eth0