Setting the Date and Time

Setting the date and time is very important for a system administrator. Why? Because if you find something inappropriate or possibly problematic in your log files (e.g., repeated unsuccessful login attempts from a specific location), you want to be able to accurately cross-reference your log files with the log files of your colleagues at the other location. That can happen only if the time on both hosts is pretty close to accurate.

To Set the Time with ntpdate:

• sudo /usr/sbin/ntpdate 192.168.96.3

  Use ntpdate with the name of a time server (currently available servers are listed at www.ntp.org) to update your system clock to the current, accurate time (Code Listing 16.7). If you get an error message about the socket being in use, use ps –ef | grep ntp to find the ntp daemon that’s running to keep your time synchronized. (If this happens, your time is probably OK and doesn’t need to be set.)

  Or

• sudo date -s "Tues Jan 27 5:30:23 → 2003"

  If your system doesn’t have ntpdate, you’ll have to set the time manually. Use sudo, date, and all the rest of the needed information. (If you need to change, say, only the time, you can just provide the time, as in sudo date –s 5:45).

Code Listing 16.7. Setting the date (and making sure it stays up-to-date) is an important root user responsibility.

[jdoe@frazz jdoe]$ sudo /usr/sbin/ntpdate
→ 192.168.96.3
27 Jan 05:26:50 ntpdate[1470]: adjust time
→ server 192.168.96.3 offset -0.004140 sec
[jdoe@frazz jdoe]$ sudo date -s 5:30
Mon Jan 27 05:30:00 MST 2003
[jdoe@frazz jdoe]$ sudo date -s "Tues
→ Jan 28 5:30:21"
Tue Jan 28 05:30:21 MST 2003
[jdoe@frazz jdoe]$ sudo date -s "Tues
→ Jan 28 5:30:21 2004"
Password:
Wed Jan 28 05:30:21 MST 2004
[jdoe@frazz jdoe]$ sudo date -s "Mon Jan
→ 27 5:30:21 2003"
Mon Jan 27 05:30:21 MST 2003
[jdoe@frazz jdoe]$ date
Mon Jan 27 05:30:35 MST 2003
[jdoe@frazz jdoe]$ sudo /usr/sbin/
→ ntpdate 192.168.96.3
27 Jan 05:30:38 ntpdate[1616]: step time
server 192.168.96.3 offset -7.329083 sec
[jdoe@frazz jdoe]$ sudo /usr/sbin/
→ ntpdate 192.168.96.3
27 Jan 05:30:44 ntpdate[1622]:adjust time
server 192.168.96.3 offset 0.000479 sec
[jdoe@frazz jdoe]$