Linux CGroup全称Linux Control Group， 是Linux内核的一个功能，用来限制，控制与分离一个进程组群的资源（如CPU、内存、磁盘输入输出等）。这个项目最早是由Google的工程师在2006年发起（主要是Paul Menage和Rohit Seth），最早的名称为进程容器（process containers）。在2007年时，因为在Linux内核中，容器（container）这个名词太过广泛，为避免混乱，被重命名为cgroup，并且被合并到2.6.24版的内核中去。然后，其它开始了他的发展。
Linux CGroupCgroup 可让您为系统中所运行任务（进程）的用户定义组群分配资源 — 比如 CPU 时间、系统内存、网络带宽或者这些资源的组合。您可以监控您配置的 cgroup，拒绝 cgroup 访问某些资源，甚至在运行的系统中动态配置您的 cgroup。
cgroups的一个设计目标是为不同的应用情况提供统一的接口，从控制单一进程到操作系统层虚拟化
主要功能:
限制进程组可以使用的资源数量（Resource limiting ）。比如：memory子系统可以为进程组设定一个memory使用上限，一旦进程组使用的内存达到限额再申请内存，就会出发OOM（out of memory）。
[root@node1 yum.repos.d]# yum install ifconfig
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org?arch=x86_64&release=7&repo=sclo-sclo error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; Unknown error"
One of the configured repositories failed (Unknown),
and yum doesn't have enough cached data to continue. At this point the only
safe thing yum can do is fail. There are a few ways to work "fix" this:
1. Contact the upstream for the repository and get them to fix the problem.
2. Reconfigure the baseurl/etc. for the repository, to point to a working
upstream. This is most often useful if you are using a newer
distribution release than is supported by the repository (and the
packages for the previous distribution release still work).
3. Run the command with the repository temporarily disabled
yum --disablerepo= ...
4. Disable the repository permanently, so yum won't use it by default. Yum
will then just ignore the repository until you permanently enable it
again or use --enablerepofor temporary usage:
yum-config-manager --disable<repoid>
or
subscription-manager repos --disable=<repoid>5. Configure the failing repository to be skipped, if it is unavailable.
Note that yum will try to contact the repo. when it runs most commands,
so will have to try and fail each time(and thus. yum will be be much
slower). If it is a very temporary problem though, this is often a nice
compromise:
yum-config-manager --save--setopt=<repoid>.skip_if_unavailable=true
Cannot find a valid baseurl for repo: centos-sclo-sclo/x86_64
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vi /etc/yum.repos.d/CentOS-Base.repo
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全选替换：
# CentOS-Base.repo## The mirror system uses the connecting IP address of the client and the# update status of each mirror to pick mirrors that are updated to and# geographically close to the client. You should use this for CentOS updates# unless you are manually picking other mirrors.## If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead.#[base]name=CentOS-$releasever - Base
baseurl=https://mirrors.aliyun.com/centos/$releasever/os/$basearch/
gpgcheck=1gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#released updates [updates]name=CentOS-$releasever - Updates
baseurl=https://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
gpgcheck=1gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#additional packages that may be useful[extras]name=CentOS-$releasever - Extras
baseurl=https://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
gpgcheck=1gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#contrib - packages by Centos Users[centosplus]name=CentOS-$releasever - Plus
baseurl=https://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1enabled=0gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
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或者
# CentOS-Base.repo## The mirror system uses the connecting IP address of the client and the# update status of each mirror to pick mirrors that are updated to and# geographically close to the client. You should use this for CentOS updates# unless you are manually picking other mirrors.## If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead.#[base]name=CentOS-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/os/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/os/$basearch/
gpgcheck=1gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#released updates [updates]name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/updates/$basearch/
gpgcheck=1gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#additional packages that may be useful[extras]name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/extras/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/extras/$basearch/
gpgcheck=1gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#additional packages that extend functionality of existing packages[centosplus]name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/centosplus/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1enabled=0gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#contrib - packages by Centos Users[contrib]name=CentOS-$releasever - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/contrib/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/contrib/$basearch/
gpgcheck=1enabled=0gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
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4、编辑 CentOS-SCLo-scl-rh.repo 文件（如果没有这个文件，不用管）
编辑 CentOS-SCLo-scl-rh.repo 文件：
vi /etc/yum.repos.d/CentOS-SCLo-scl-rh.repo
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