Abstract
As the series work about the improvement of vacuum DAQ, I set the timing synchronization on RaspPi.(Timestamp in log files was ~a few years different from the correct time, so it's difficult to check the log investigation.)
A direct cause of wrong system time was due to the settings of DNS not NTP.
After reseting DNS, RaspPi system is synchronized by systemd-timesyncd.
Details
At first, I tried to install the some package for synchronizing the server time. But RaspPi couldn't access the standard repositories. After some checks, I found that this was caused by wrong DNS settings. In 2020, large update of ICRR network was done and the server addresses of DNS in ICRR LAN were also changed at that time. But list of nameserver on RaspPi was still old address. Because nameservers are managed by resolvconf, I modified /etc/resolvconf.conf as name_servers=x.x.x.x and restarted NIC by ifdown eth0 && ifup eth0. After then, list of nameservers in /etc/resolv.conf was updated as correct servers and I got an access to standard repositories.As the next, I planned to install ntpd or chronyd. But I found timestamp of logs became already correct and systemd-timesyncd was running. Probably, RaspPi had been synchronized properly around 2018(?) when this system was installed for the first time. They had just been left unsynchronized since the network change in 2020. Anyway, RaspPi system is now synchronized and a log-file analysis will be getting easier.