Slackware's package management is a very simplistic one compared to dpkg or rpm for example. This makes it easy to create your own packages, gives you a maximum of flexibility and is in keeping with the KISS principle of the distribution.
However, this also means that mistakes either in the creation of packages or in their installation can easily be done, resulting potentially in a system that behaves 'oddly' and in difficult to track down problems.
pkgcheck is a collection of tools that allows you to detect some of these problems. The original Slackware tools are not touched; instead, these utilities are used either before or after an installation. See the chapter "Use Cases" for a description on how to use the tools.
These tools try hard to detect potential problems; however, it's up to the system administrator to decide whether there is a real problem or not.
If you create packages yourself, always check the resulting package: "pkgcheck <package>"
vlpcheck can do a few checks to find potential problems in an installation. In doubt, issue a "vlpcheck update" before proceeding.
"vlpcheck duppacks" will detect if packages with the same name but different versions have been installed. This is usually the result of having installed a package with "installpkg" instead of "upgradepkg" when there was already an older version on the system. It should be enough to "removepkg" the older package(s). In doubt, remove them all and reinstall the lastest package.
"vlpcheck dupfiles" will find files that belong to more than one installed package. This may be a problem in the sense that the order of installation of packages results in either the file from the one or the other package being installed on the harddisk.
If you run this check for the first time, it will result in an awful lot of error messages. This is due to the fact that Slackware duplicates some files on purpose. However, information in the package database is not enough to find out whether the files are really identical, so this check needs a second pass, namely looking inside the source packages.
At the end of the list, you'll see the packages that need to be investigated (they are preceeded by a '-'). Copy the original packages to /var/lib/vlpcheck and re-run "vlpcheck dupfiles". The number of duplicate files should be lower, but due to the way in which vlpcheck works it might now ask for some more packages (preceded by '-'), while the packages it has successully checked are preceeded by a '+'. Repeat the operation until there are no more packages at the end of the list which are preceeded by a '-'.
For reference, an initial check of a Slackware 11.0 full install (without any patches) detected 6918 duplicates. After 2 iterations, the number of problematic files was down to 28.
Orphans are usually files which have been installed manually or from source. Use "vlpcheck orphans" for a list.
Ghosts are files which are listed in the package database but which are no longer present. This is OK for some files (such as .new configuration files), but may be a problem if you removed things manually. Use "vlpcheck ghosts" for a list.
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