sudo emerge -1 --ask dev-lang/ruby --keep-going --nodeps

--autounmask-backtrack < y | n >Allow backtracking after autounmask has detected that configuration changes are necessary. This option is not recommended, since it can cause a large amount of time to be wasted by backtracking calculations, even though there is no guarantee that it will produce a solution. This option is disabled by default.

emergeのオプション。

時間かかるけど、解決出来る保証はないよってこと？ひどいオプションだなあ。

自動でマスク解除するけど、コンフリクトとか出たら、backtrack(後戻り)するよって意味。

PYTHON_USEDEP

Contains a USE dependency string that can be used to enforce matching Python implementations on package dependencies. It must be used on package dependencies which are using the python-r1

PYTHON_USEDEPはpython系のパッケージのebuildファイルの中で出てくる変数で、多分ビルドに使うpythonのバージョンを表しています。

--backtrack=COUNT

Specifies an integer number of times to backtrack if dependency calculation fails due to a conflict or an unsatisfied dependency (default: '10').

　のオプションnumber of times後戻りするって言ってるけど、戻る単位が何なのかわからない。

emerge: error: Invalid Atom(s) in --reinstall-atoms parameter: 'media-gfx/uniconvertor-2.0_pre379-r2' (only package names and slot atoms (with wildcards) allowed)

grep -R dogtail /etc/portage/ | grep -v "#"

USEフラグの探し方