Inside a crontab File

The cron daemon schedules system tasks according to commands found within each crontab file. A crontab file consists of commands, one command per line, that will be executed at regular intervals. The beginning of each line contains date and time information that tells the cron daemon when to execute the command.

For example, a crontab file named root is supplied during SunOS software installation. The file's contents include these command lines:

10 3 * * * /usr/sbin/logadm (1)
15 3 * * 0 /usr/lib/fs/nfs/nfsfind (2)
1 2 * * * [ -x /usr/sbin/rtc ] && /usr/sbin/rtc -c > /dev/null 2>&1 (3)
30 3 * * * [ -x /usr/lib/gss/gsscred_clean ] && /usr/lib/gss/gsscred_clean (4)

The following describes the output for each of these command lines:

• The first line runs the logadm command at 3:10 a.m. every day.

• The second line executes the nfsfind script every Sunday at 3:15 a.m.

• The third line runs a script that checks for daylight savings time (and make corrections, if necessary) at 2:10 a.m. daily.

  If there is no RTC time zone, nor an /etc/rtc_config file, this entry does nothing.

  ---

  x86 only –

  The /usr/sbin/rtc script can only be run on an x86 based system.

  ---

• The fourth line checks for (and removes) duplicate entries in the Generic Security Service table, /etc/gss/gsscred_db, at 3:30 a.m. daily.

For more information about the syntax of lines within a crontab file, see Syntax of crontab File Entries.

The crontab files are stored in the /var/spool/cron/crontabs directory. Several crontab files besides root are provided during SunOS software installation. See the following table.

Besides the default crontab files, users can create crontab files to schedule their own system tasks. Other crontab files are named after the user accounts in which they are created, such as bob, mary, smith, or jones.

To access crontab files that belong to root or other users, superuser privileges are required.

Procedures explaining how to create, edit, display, and remove crontab files are described in subsequent sections.