tw_cron_update

The tw_cron_update utility is used to manage tideway user cron.

To use the utility, type the following command at the $TIDEWAY/bin/ directory:

tw_cron_update

Cron overview

BMC Discovery makes use of cron on the appliance to run various housekeeping tasks. This means that crontab must not be directly edited on the appliance, but must instead be managed using tw_cron_update. This way, BMC Discovery can manage cron entries across upgrades without affecting, or being affected by, any local customizations.

Cron entries are stored in $TIDEWAY/etc/cron. Each cron entry has its own file, using the file extension .cron to identify that file. A cron entry is created by adding a new file ending with .cron containing standard cron formatted commands. Similarly entries can be edited or removed by editing or removing .cron files.

$TIDEWAY/bin/tw_cron_update checks, every time it is run, that the file has not been edited since tw_cron_update was last run.

A note on the format of a cron entry is provided in the tw_cron.header file:

#******************************************************************
# The Tideway crontab file should NOT be edited manually.
# Please add or edit .cron files in $TIDEWAY/etc/cron and then run
# $TIDEWAY/bin/tw_cron_update to update changes.
#
# crontab format:
# min (0-59) hour (0-23) day(1-31) month(1-12) wkday(1-7) command
# ex: 30 23 * * * rm /home/someuser/tmp/*
#******************************************************************
MAILTO=""

For full details, see the Red Hat Enterprise Linux version 7 cron documentation as this applies equally to CentOS.

Managing cron entries

Cron entry files in $TIDEWAY/etc/cron are applied to the live cron configuration by running $TIDEWAY/bin/tw_cron_update as the tideway user.

• Run $TIDEWAY/bin/tw_cron_update as the tideway user. Every time the script is run it confirms that the current live cron configuration matches what BMC Discovery expects it to be. If the configuration is as expected, there will be no output. If there is a discrepency, an appropriate message will be displayed, and the discrepency must be resolved before continuing.

• To add a new cron entry, add a new .cron file. For example, the following file runs the tw_supportability command daily at 23:45:

  [tideway@appliance01 cron]$ more tw_appliance_stats.cron
  #
  # cron job to capture disk and cpu daily usage
  # runs every day at 23:45
  #
  45 23 * * * /usr/tideway/bin/tw_supportability

• To remove a cron entry, remove its .cron file, or modify the file extension to something other than .cron, (for example, .disabled.
• To modify a cron entry, edit its .cron file.
• Run $TIDEWAY/bin/tw_cron_update as the tideway user.