If you've added (or removed) some USE flags on your system, there will be some inconsistencies with how some packages are compiled.
equery uses packagename
equery hasuse useflag
equery hasuse ldap [ Searching for USE flag ldap in all categories among: ] * installed packages [I--] [ ] app-crypt/gnupg-1.2.6 (0) [I--] [ ] dev-libs/cyrus-sasl-2.1.20 (2) [I--] [ ] dev-php/php-4.3.10 (0) [I--] [ ] kde-base/kdebase-3.3.2-r1 (3.3) [I--] [ ] kde-base/kdelibs-3.3.2-r2 (3.3) [I--] [ ] mail-client/evolution-1.4.6 (0) [I--] [ ] mail-client/pine-4.61-r2 (0) [I--] [ ] net-fs/samba-3.0.9-r1 (0) [I--] [ ] net-misc/openssh-3.9_p1-r1 (0) [I--] [ ] net-www/mozilla-firefox-1.0 (0) [I--] [ ] net-www/mozilla-1.7.5 (0)
If you make major changes to your USE flags, and want to rebuild your entire system to make use of this, you can either run
emerge --emptytree world
This will, however, rebuild everything. If you've changed your CFLAGS then that might make sense, but if you've only changed some USE flags and want to rebuild everything that might make use of it, try the following instead:
emerge --newuse world
This will only rebuild packages whose USE flags would change
This happens a lot. If you run emerge -Du world, and don't have a tediously slow machine, chances are pretty good that at some point you'll emerge a package which will "automatically" overwrite some config option. It'll tell you about it, but you probably won't be watching. The shadow package was doing this for a while, and was overwriting the PAM configuration -- screwing anyone who used any non-standard PAM options.
The last two options are ok, however this should be part of portage, not an external script. There is a bug filed against portage for this, but it's been about two years and nothing has actually happened. It's possible this will be included in the 'next version of portage', whenever that comes out.
You can set specific USE flags for a given package in the package attribute /etc/portage/package.use. Those flags will then be applied to that package as though they were specified on the CommandLine. Eg., to build BitTorrent without X11 support:
echo net-p2p/bittorrent -X >> /etc/portage/package.use
Packages can be flagged as masked for a number of reasons. Mostly they are masked because they might break something, or they WILL break something. These tend to be masked in /usr/portage/profiles/packages.mask, and you can either forcibly install the package (see later), or unmask the package by commenting out the line. Note that this file is rebuilt everytime you emerge sync. There is a packages.unmask file, which allows you to unmask packages that have been explicitly masked, but use this with care: The package was probably masked for a good reason. You can look in /usr/portage/profiles/package.mask to see what packages are masked and why, and copy the declaration to /etc/portage/packages.unmask to unmask it.
The other reason packages can be masked is that they are in the 'unstable' branch of the gentoo tree. This is essentially the same as unstable in debian. Sometimes things will break, othertimes they'll be fine. You're on your own.
The only recommended way to install masked packages is to add to /etc/portage/package.keywords an entry for the package you want to build. Do not, whatever you do, emerge the .ebuild directly, or try to override ACCEPT_KEYWORDS on the CommandLine. Eg., if you want to emerge XFce4 from the unstable tree, do:
echo 'wm-x11/xfce4 ~x86' >> /etc/portage/package.keywords echo '=wm-x11/xfce4-4.0.0 ~x86' >> /etc/portage/package.keywords # specific version of the package echo '~wm-x11/xfce4-4.0.0 ~x86' >> /etc/portage/package.keywords # all revisions of a specific version
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