Example

A brand new file is required in /etc to provide the necessary information to support the solid state hard disk, named /etc/shdisk.conf. The entry in the pkgmap file might look like this:

 
.
.
.
1 f newetc /etc/shdisk.conf
.
.
.

The class action script i.newetc is responsible for installing this and any other files that need to go into /etc. It checks to make sure there is not another file there. If there is not, it will simply copy the new file into place. If there is already a file in place, it will back it up before installing the new file. The script r.newetc removes these files and restores the originals, if required. Here is the key fragment of the install script.

# i.newetc
while read src dst; do
	  if [ -f $dst ]; then
	    dstfile=`basename $dst`
	    cp $dst $PKGSAV/$dstfile
	  fi
	  cp $src $dst
done
 
if [ "${1}" = "ENDOFCLASS" ]; then
	  cd $PKGSAV
	  tar cf SAVE.newetc .
	  $INST_DATADIR/$PKG/install/squish SAVE.newetc
fi

Notice that this script uses the PKGSAV environment variable to store a backup of the file to be replaced. When the argument ENDOFCLASS is passed to the script, that is the pkgadd command informing the script that these are the last entries in this class, at which point the script archives and compresses the files that were saved using a private compression program stored in the install directory of the package.

While the use of the PKGSAV environment variable is not reliable during a package update; if the package is not updated (through a patch, for instance) the backup file is secure. The following remove script includes code to deal with the other issue—the fact that older versions of the pkgrm command do not pass the scripts the correct path to the PKGSAV environment variable.

The removal script might look like this.

# r.newetc
 
# make sure we have the correct PKGSAV
if [ -d $PKG_INSTALL_ROOT$PKGSAV ]; then
	  PKGSAV="$PKG_INSTALL_ROOT$PKGSAV"
fi
 
# find the unsquish program
UNSQUISH_CMD=`dirname $0`/unsquish
 
while read file; do
	  rm $file
done
 
if [ "${1}" = ENDOFCLASS ]; then
	  if [ -f $PKGSAV/SAVE.newetc.sq ]; then
	     $UNSQUISH_CMD $PKGSAV/SAVE.newetc
	  fi
 
	  if [ -f $PKGSAV/SAVE.newetc ]; then
	     targetdir=dirname $file	# get the right directory
	     cd $targetdir
		    tar xf $PKGSAV/SAVE.newetc
		    rm $PKGSAV/SAVE.newetc
	  fi
fi

This script uses a private uninstalled algorithm (unsquish) which is in the install directory of the package database. This is done automatically by the pkgadd command at install time. All scripts not specifically recognized as install-only by the pkgadd command are left in this directory for use by the pkgrm command. You cannot count on where that directory is, but you can depend on the directory being flat and containing all appropriate information files and installation scripts for the package. This script finds the directory by virtue of the fact that the class action script is guaranteed to be executing from the directory that contains the unsquish program.

Notice, also, that this script does not just assume the target directory is /etc. It may actually be /export/root/client2/etc. The correct directory could be constructed in one of two ways.

• Use the ${PKG_INSTALL_ROOT}/etc construction, or.

• Take the directory name of a file passed by the pkgadd command (which is what this script does).

By using this approach for each absolute object in the package, you can be sure that the current desirable behavior is unchanged or at least recoverable.