Transactions allow you to install multiple packages as a group and know that either all the packages will succeed in installing or none of them will. This is very important if you have a set of interlocking packages that you need to install.

All the packages you install, remove, or upgrade on the same command line are automatically made part of a transaction. The rpm command will ensure that all packages can be installed, removed, or upgraded, and will not perform the operation unless all will succeed.

All packages installed or removed are given a transaction ID, which uses a Unix timestamp (the number of seconds since January 1, 1970). All packages installed or removed at the same time are given the same transaction ID. You can then query by transaction IDs to perform operations on all the packages installed together.

The --repackage option tells the rpm command to make a backup RPM of the current package when you are installing or upgrading a more recent version or removing the package. By default, the backup RPM is placed in the /var/spool/repackage directory. Note that a package created this way is not exactly the same as the original package. Files may have changed on disk. In addition, packages created with the --repackage option are not real valid RPM packages. You cannot install these packages without performing extra operations to create a real RPM package from the repackaged data.