Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Configuring a System
Making Adjustments
Chapter 3 267
Making Adjustments
• Setting the System Clock
• Manually Setting Initial Information
• Customizing System-Wide and User Login Environments
Setting the System Clock
Only the superuser (root) can change the system clock. The system clock
budgets process time and tracks file access.
Potential Problems When Changing the System Clock
The following are potential problems you can cause by changing the
system clock:
• The make program is sensitive to a file’s time and date information
and to the current value of the system clock. Setting the clock
forward will have no effect, but setting the clock backward by even a
small amount may cause make to behave unpredictably.
• Incremental backups heavily depend on a correct date because the
backups rely on a dated file. If the date is not correct, an incorrect
version of a file can be backed up.
• Altering the system clock can cause unexpected results for jobs
scheduled by /usr/sbin/cron:
— If you set the time back, cron does not run any jobs until the
clock catches up to the point from which it was set back. For
example, if you set the clock back from 8:00 to 7:30, cron will not
run any jobs until the clock again reaches 8:00.
— If you set the clock ahead, cron attempts to catch up by
immediately starting all jobs scheduled to run between the old
time and the new. For example, if you set the clock ahead from
9:00 to 10:00, cron immediately starts all jobs scheduled to run
between 9:00 and 10:00.