Problem: When upgraded DirectControl to the latest version, /etc/dzshrc is overwritten and needed to manually restore its content.
Cause: /etc/dzshrc is part of the package therefore it is replaced during upgrade.
Workaround: 1) In pre-installation, save a copy of /etc/dzshrc to /etc/dzshrc.pre_cdc_upgrade: cp /etc/dzshrc /etc/dzshrc.pre_cdc_upgrade
2) In post-installation, compare the newly installed /etc/dzshrc with the one we saved before upgrade. If the files are the same, remove the saved copy. Otherwise, replace the /etc/dzshrc with /etc/dzshrc.pre_cdc_upgrade. This is to preserve the customized copy of dzshrc.
3) For AIX, need to fix both *.pre_i and *.pre_rm because *.pre_rm may be skipped.