解密conda channels
conda config --show channels
channels:
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/main/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/conda-forge/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/bioconda/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/menpo/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/msys2/
- defaults>https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free/
每个url对应的是不同操作系统平台的文件夹
在操作系统对应的目录下，是具体的安装包，后缀为tar.bz2
>https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free/linux-64/
在这些安装包中，有一个比较特殊repodata.json， 存储了该目录下包含的所有包的名称，依赖，md5等信息
部分内容如下
{
"info": {
"arch": "x86_64",
"platform": "linux",
"subdir": "linux-64"
},
"packages": {
"_libgcc_mutex-0.1-free.tar.bz2": {
"build": "free",
"build_number": 0,
"date": "2019-07-01",
"depends": [],
"md5": "f7d7639c8485ae4701aeb6add534a774",
"name": "_libgcc_mutex",
"size": 3129,
"timestamp": 1562011672620,
"track_features": "free_channel_libgcc",
"version": "0.1"
},
"_license-1.1-py27_0.tar.bz2": {
"build": "py27_0",
"build_number": 0,
"date": "2013-03-01",
"depends": [
"python 2.7*"
],在安装包的时候，conda会依次遍历所有的channnels,通过repodata来查找该channel是否包含需要下载的packages, 一个基本的安装过程如下
conda create -n myenv numpy
Collecting package metadata (current_repodata.json): done
Solving environment: done
## Package Plan ##
environment location: /media/gsadmin/vd1/heguangliang/bcbio3/anaconda/envs/myenv
added / updated specs:
- numpy
The following packages will be downloaded:
package | build
---------------------------|-----------------
blas-1.0 | mkl 6 KB https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free
numpy-1.13.1 | py36_0 7.2 MB https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free
------------------------------------------------------------
Total: 7.2 MB
The following NEW packages will be INSTALLED:
blas anaconda/pkgs/free/linux-64::blas-1.0-mkl
certifi anaconda/pkgs/free/linux-64::certifi-2016.2.28-py36_0
mkl anaconda/pkgs/free/linux-64::mkl-2017.0.3-0
numpy anaconda/pkgs/free/linux-64::numpy-1.13.1-py36_0
openssl anaconda/pkgs/free/linux-64::openssl-1.0.2l-0
pip anaconda/pkgs/free/linux-64::pip-9.0.1-py36_1
python anaconda/pkgs/free/linux-64::python-3.6.2-0
readline anaconda/pkgs/free/linux-64::readline-6.2-2
setuptools anaconda/pkgs/free/linux-64::setuptools-36.4.0-py36_1
sqlite anaconda/pkgs/free/linux-64::sqlite-3.13.0-0
tk anaconda/pkgs/free/linux-64::tk-8.5.18-0
wheel anaconda/pkgs/free/linux-64::wheel-0.29.0-py36_0
xz anaconda/pkgs/free/linux-64::xz-5.2.3-0
zlib anaconda/pkgs/free/linux-64::zlib-1.2.11-0
Proceed ([y]/n)?
Downloading and Extracting Packages
numpy-1.13.1 | 7.2 MB | ################################################################################################################################# | 100%
blas-1.0 | 6 KB | ################################################################################################################################# | 100%
Preparing transaction: done
Verifying transaction: done
Executing transaction: done
#
# To activate this environment, use
#
# $ conda activate myenv
#
# To deactivate an active environment, use
#
# $ conda deactivate
对于某些不能用的镜像，会在下载repodata.json时失效，出现如下所示的报错
conda create -n myenv ggtree
Collecting package metadata (current_repodata.json): failed
CondaHTTPError: HTTP 000 CONNECTION FAILED for url <https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/conda-forge/linux-64/current_repodata.json>
Elapsed: -
An HTTP error occurred when trying to retrieve this URL.
HTTP errors are often intermittent, and a simple retry will get you on your way.
ConnectionError(ReadTimeoutError("HTTPSConnectionPool(host='mirrors.tuna.tsinghua.edu.cn', port=443): Read timed out.",),)
此时我们就需要确认下该镜像是失效了，还是因为网络原因，如果失效的话，就考虑删除这个镜像。
当网络波动时，会出现下载失败的情况，报错如下
CondaHTTPError: HTTP 000 CONNECTION FAILED for url <https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/main/win-64/mkl-2020.2-256.conda>
Elapsed: -
An HTTP error occurred when trying to retrieve this URL.
HTTP errors are often intermittent, and a simple retry will get you on your way.
此时镜像本身是没问题的，就是下载速度慢，导致下载失败，只需要多试几次即可。
对于channels而言，我们需要学会新增和删除，对应的操作如下
1. 删除
conda config --remove channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/conda-forge/2. 增加
conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free/config子命令的本质是在操作.condarc这个配置文件，所以我们直接在这个配置文件里进行修改也是可以的，condarc的内容示例如下
channels:
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/main/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/bioconda/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/menpo/
- https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/msys2/
- defaults
ssl_verify: false
show_channel_urls: true修改镜像的使用场景有以下两种，第一种是使用国内镜像，提高下载速度，第二种是为了下载特定镜像才包含的packages。镜像的修改非常简单，关键是要理解镜像的本质。