@asdf12303116 #25 一直这样吗？还是最近改的？以前没注意，都是直接换国内源。

@totoro52 #23 我的是 20.04 ，不是新版本，也会跳到清华源。应该是服务端做了重定位。

@ziwen1943 #16 了解了，感谢。

@unclemcz #18 我开代理不跳，关了代理就跳到清华源了。应该是楼上大哥说的那种机制。

@vicacheung #11 是吗？那以后是不是不需要手动换源了？

@ysc3839 #9
```
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://cn.archive.ubuntu.com/ubuntu/ focal universe
# deb-src http://cn.archive.ubuntu.com/ubuntu/ focal universe
deb http://cn.archive.ubuntu.com/ubuntu/ focal-updates universe
# deb-src http://cn.archive.ubuntu.com/ubuntu/ focal-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://cn.archive.ubuntu.com/ubuntu/ focal multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ focal multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ focal-updates multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ focal-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://cn.archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu focal partner
# deb-src http://archive.canonical.com/ubuntu focal partner

deb http://security.ubuntu.com/ubuntu focal-security main restricted
# deb-src http://security.ubuntu.com/ubuntu focal-security main restricted
deb http://security.ubuntu.com/ubuntu focal-security universe
# deb-src http://security.ubuntu.com/ubuntu focal-security universe
deb http://security.ubuntu.com/ubuntu focal-security multiverse
# deb-src http://security.ubuntu.com/ubuntu focal-security multiverse
```
都是自带的，我没改过。

@dangyuluo #6 没有。一切正常，可以更新缓存。我好奇他到底配置到哪儿了。

@czphoenix #5 没有。我 grep 了整个 apt 目录，没有发现 tsinghua 的字段。

@anytk #2 这个怎么看？从哪儿看出来有清华源？

@cheng6563 #1 那它不会添加到 source.list 文件中吗？

@hitmanx #18 我的意思是根据参数创建对应个数的条件变量的实例。vector 里的指针不是指向一个条件变量，而是指向参数个条件变量。

@hitmanx #10 但是我需要多个条件变量，数量也不想写死。而是能在类实例化时用参数指定。

@cnbatch #9 那你的 vector 里面的元素数量是写死的？还是在初始化时可以根据参数设置？

@cnbatch #5 无论怎么 back ，调用的都是拷贝构造函数。条件变量把拷贝构造函数删了，也就是不允许复制。

@sheyueji #2 那我也需要有条件变量的实例。我就是要在初始化时根据参数指定的数量创建条件变量的个数。

@crissx #1 牛啊。说的好详细啊。

国内说的是中国大陆吗？会上架 pixel ？那不就相当于在中国销售了吗？

现在哪个平台最好？