多数发行版都会自动更新所有添加的源，包括第三方源，如redhat系、debian系、arch linux等，而Gentoo添加了第三方源（overlay）之后，更新时，需要用layman -S命令来单独更新全部overlay。
现在，最新的portage管理器也终于支持用emerge命令来更新overlay了！
2015-02-04-portage-sync-changes
Title New portage plug-in sync system
Author Brian Dolbec <dolsen@gentoo.org>
Posted 2015-02-02
Revision 1
There is a new plug-in sync system in >=sys-apps/portage-2.2.16.
This system will allow third party modules to be easily installed. Look
for a new layman plug-in sync module in layman's next release. Next is
a brief look at the changes. See the url [1] listed below for detailed
descriptions and usage.
Changes: /etc/portage/repos.conf/*
New setting for all repository types (needed):
auto-sync = yes/no, true/false # default if absent: yes/true
New for git sync-type: (applies to clone only)
sync-depth = n where n = {0,1,2,3,...} (optional, default = 1)
0 -- full history
1 -- shallow clone, only current state (default)
2,3,... number of history changes to download
New sync-type modules:
sync-type = svn # sync a subversion repository
sync-type = websync # Perform an emerge-webrsync operation
sync-type = laymanator # (if installed) runs a layman -s action
New native portage postsync hooks
/etc/portage/postsync.d/*
Runs hooks once, only after all repos have been synced.
/etc/portage/repo.postsync.d/*
Runs each script with three arguments:
repo name, sync-uri, location
Each script is run at the completion of every repo synced.
Migration:
Edit /etc/portage/repos.conf/*.conf files, add the auto-sync option
to each repository definition. Edit sync-type option to one of the
supported types {rsync, git, cvs, svn, websync, laymanator}.
[some-repo]
...
sync-type = rsync
auto-sync = yes
For an existing /etc/portage/repos.conf/layman.conf file:
1) change/add the sync-type
sync-type = laymanator
2) Ensure you have the correct layman version installed with
it's laymanator module also installed.
Alternate method:
Please see the wiki page url [1] for detailed instructions.
Primary control of all sync operations has been moved from emerge to
emaint. "emerge --sync" now just calls the emaint sync module with the
--auto option. The --auto option performs a sync on only those
repositories with the auto-sync setting not set to 'no' or 'false'. If
it is absent, then it will default to yes and "emerge --sync" will sync
the repository.
NOTE: As a result of the default auto-sync = True/Yes setting, commands
like "eix-sync", "esync -l", "emerge --sync && layman -S" will cause
many repositories to be synced multiple times in a row. Please edit
your configs or scripts to adjust for the new operation.
WARNING:
Due to the above default. For any repos that you EXPLICITLY do not
want to be synced. You MUST set "auto-sync = no"
The 'emaint sync' module operates similar to layman. It can sync
single or multiple repos. See "emaint --help" or for more details and
examples see the wiki page listed below [1].
Additional help and project API documentation can be found at:
[1] https://wiki.gentoo.org/wiki/Project:Portage/Sync
也就是从sys-apps/portage-2.2.16开始，添加了配置文件之后，用emerge –sync就可以直接更新overlay了。另外，layman也增加了一个use，sync-plugin-portage（Install the sys-apps/portage sync module），默认不开启。如果需要手动配置，可以采用以下方法：
1、首先，需要创建一个配置文件。安装portage和layman时没有自动创建文件和目录，只好手动创建了。
mkdir /etc/portage/repos.conf touch /etc/portage/repos.conf/layman.conf
2、手动添加配置信息，例如gentoo-zh：
[gentoo-zh] location = /var/lib/layman/gentoo-zh auto-sync = yes sync-type = git sync-uri = https://github.com/microcai/gentoo-zh.git
注：有了配置文件之后，新安装的overlay也会自动添加配置文件，但需要修改，否则更新时出错。这是默认添加的配置：
[kde] priority = 50 location = /var/lib/layman/kde auto-sync = No layman-type = git
有三个地方需要修改：auto-sync的No修改为yes；layman-type改为sync-type；按前面配置方式添加sync-uri项。改成下面内容：
[kde] priority = 50 location = /var/lib/layman/kde auto-sync = yes sync-type = git sync-uri = https://github.com/gentoo/kde.git
配置完成。
以后，再用emerge –sync更新portage时，官方portage更新完成之后，会自动更新overlay，出现如下信息：
>>> Syncing repository 'gentoo-zh' into '/var/lib/layman/gentoo-zh'...
/usr/bin/git pull
remote: Counting objects: 15, done.
remote: Compressing objects: 100% (15/15), done.
remote: Total 15 (delta 4), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (15/15), done.
From git://github.com/microcai/gentoo-zh
da7bbf3..a4d1c13 master -> origin/master
Updating da7bbf3..a4d1c13
Fast-forward
media-video/bilibili-player/Manifest | 2 +-
media-video/bilibili-player/{bilibili-player-0.10.ebuild => bilibili-player-0.12.ebuild} | 8 ++++++--
2 files changed, 7 insertions(+), 3 deletions(-)
rename media-video/bilibili-player/{bilibili-player-0.10.ebuild => bilibili-player-0.12.ebuild} (88%)
=== Sync completed for gentoo-zh
>>> Syncing repository 'kde' into '/var/lib/layman/kde'...
/usr/bin/git pull
Already up-to-date.
=== Sync completed for kde