Project:Portage/FAQ

How can "blocks" between packages be resolved?
See the Blocked Packages section in the Gentoo Handbook.

Why is it that emerge does not update all packages?
By default, the dependency graph may not include some packages. For example, it will not include any packages that are listed in the output of. It will also not include any build time dependencies for installed packages or binary packages. If you would like to include such build time dependencies even though they are not strictly required, use. You can set  in  if you would like this option to be enabled by default. If you would like a specific package to be updated in any case, you can use to have it added to the world set.

After running, it is a good idea to use to see if there are any packages that it would remove. If that command shows a package that you would like to keep, use to have it added to the world set.

How can I check for reverse dependencies of a package, to know if it can be safely uninstalled?
Run to see if there are any reverse dependencies for matched packages.

Why does emerge --depclean sometimes remove system packages?
For system dependencies that are specified as virtuals, such as, it's common to have multiple packages installed that are capable of satisfying the dependency. In this case, redundant packages may be removed by unless they are explicitly added to the world set. You can use to have a package added to the world set, and this will guarantee that this package will not be removed by.

Why doesn't emerge account for reverse dependencies sometimes?
Complete accounting for reverse dependencies is time-consuming, and many users would be likely to complain about poor performance if this was the default behavior. So, reverse dependencies will often be neglected by dependency calculations unless the option is enabled. You can set  in  if you would like this option to be enabled by default. Refer to the manual page (run ) for more information about the   option.

Can I mount the Portage tree (/usr/portage) via NFS?
It is possible to share the Portage tree over NFS so that  only needs to be run on an NFS server. However, even though NFS clients do not need to run, they must run each time that the Portage tree is updated since otherwise their dependency calculations will slow down due to their metadata cache (located in ) becoming stale.

If you encounter problems with an NFS setup it is important that you ensure you have the proper locking daemons on both the NFS client machines and the NFS server machine. Portage uses hardlinks over NFS in an attempt to lock files; if the locking daemon fails to lock files Portage may complain about failed or stale locks. There is a script that can be used to clean out old lockfiles.

Why does emerge display "waiting for lock" messages?
The most common reason is due to  which is enabled by default in. Set  in  if you would like to disable this feature. Refer to the manual page (run ) for more information about possible FEATURES values.

If the command is invoked multiple times concurrently, or if DISTDIR location is on a shared network file system, this may also trigger similar "waiting for lock" messages. Such locks are necessary in order to prevent interference between concurrently running processes.

Why does the @preserved-rebuild set contain packages that have already been rebuilt?
This is a common problem which indicates that the build system for the given ebuild causes the package to inappropriately link against the old (preserved) version of the library, instead of the new one. As a workaround, you can manually remove the old library (such as libreadline.so.5.2) and then run in order to rebuild the packages which linked against it. A list of all preserved libraries may be obtained from.

When packages are built in parallel with the --jobs option, why aren't some packages installed immediately after they have finished building?
As a safety precaution, installation actions for system packages and their deep dependencies are executed only when no other packages are building. This behavior is required in order to avoid cases like (unspecified system dependencies) and  (temporarily unsatisfied system dependencies).

Why doesn't emerge --pretend output show the correct SLOT for a package with USE=multislot enabled?
Since ebuilds that support  violate established rules about "constant metadata", cached SLOT value differs from the SLOT value that you will actually get once the package is installed. There is nothing portage can do about this except to implement an extension such as.

How do I configure environment variable settings that apply only to specific packages?
Put an entry such as  in, and put your variable settings in  (using the same format as ). An example file might appear as follows:

What should I do when emerge reports a lot of dependency conflicts involving built slot-operator (foo/bar:X/Y=) dependencies?
Built slot-operator (foo/bar:X/Y=) dependencies tend to introduce a lot of noise when emerge dependency calculations fail. If you encounter this problem, then you should temporarily add the emerge  and   options to your emerge command, in order to suppress noise related to built slot-operator dependencies so that it is easier to identify issues that are more important. This problem is tracked by.

It addition to the  and   options mentioned above, it can also be helpful to temporarily add   to the emerge options, so that the dependency resolver does not spend extra time backtracking before it ultimately fails. Also, it can be helpful to use  instead of , so that emerge will ask you if you would like to write configuration changes that have been automatically generated by the   option.

Also see Built Slot Operator Dependency Conflicts.

What should I do if emerge fails to solve conflicts when there are "no parents that aren't satisfied by other packages in this slot"?
This is a known issue, reported in. If the conflict solely involves built slot-operator (foo/bar:X/Y=) dependencies (the  option can help you determine this), then you should temporarily add the emerge   and   options to your emerge command, as discussed in the answer to the previous question. Otherwise, it may be necessary to solve the conflict by masking one of the packages with package.mask.

Why is there a dependency conflict whey I attempt to upgrade a single package?
Attempts to upgrade single packages will often trigger dependency conflicts because emerge does not have an option to specify that it should automatically update reverse dependencies as needed. As discussed in, there are plans to implement an option for automatically update of reverse dependencies. Meanwhile, the recommended practice is to update all packages together (after each operation), using a command such as.