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建站的时候租用了一台服务器，centos的操作系统。上面只放了两个网站， CPU使用率基本为零，偶尔操作的时候也只有40%，闲置是极大的浪费。资料说门罗币（monero）可以用cpu挖，那我也挖门罗币吧。
首先要有钱包地址，本地钱包或者在线钱包，我选择了后者，所以前者就不多说了。在线平台有很多，网友说这家还不错 https://mymonero.com/ ， https://hitbtc.com/ ，注册账号之后在account里找到钱包地址，下面会用到。
接下来要在服务器上安装挖矿工具，以下命令复制粘贴。安装运行需要的程序后，从fireice-uk获取源码并编译安装，此处可以修改捐赠比例，默认是2%。实际上安装的时候不用这么麻烦，但是原来的方法不记得了，这里记录一下这个低效的方法。
sudo yum -y install centos-release-scl epel-release
sudo yum -y install cmake3 devtoolset-7-gcc* hwloc-devel libmicrohttpd-devel openssl-devel make
sudo scl enable devtoolset-7 bash
git clone https://github.com/fireice-uk/xmr-stak.git
mkdir xmr-stak/build
cd xmr-stak/build
cmake3 -DCMAKE_LINK_STATIC=ON -DXMR-STAK_COMPILE=generic -DCUDA_ENABLE=OFF -DOpenCL_ENABLE=OFF ..
make install
然而总是在42%时出错，在网上找到了这个办法。清除后重新编译。后来发现这个错误也不是每次都会出现，这还看人品？
mkdir xmr-stak/build
cd xmr-stak/build
export CFLAGS=”-O2 -march=native -msse3 -fomit-frame-pointer -pipe”
export CHOST=”x86_64-pc-linux-gnu”
export CXXFLAGS=”${CFLAGS}”
export LDFLAGS=”-Wl,-O1″
cmake3 .. -DCUDA_ENABLE=OFF -DOpenCL_ENABLE=OFF
make -j 8

安装成功之后输入/usr/local/bin/cmake –version视版本略有不同，然后修改config.txt文件，在文件中的109行-111行填入矿池钱包地址等信息，端口3333难度较低笔记本也可以算，5555，7777和9999要求都较高，文件中有照着来就可以。将26行左右cpu_threads_conf及随后中括号前的星号删除。
输入接下来的命令就可以挖矿了。
cd /root/xmr-stak/bin/
./xmr-stak-cpu
但是有时会遇到MEMORY ALLOC FAILED: mmap failed的问题，停止运行后进入/etc/security/limits.conf，在文末添加

soft memlock 262144

hard memlock 262144
保存并退出，输入下面的命令后重启。一般这样问题就解决了。

sysctl -w vm.nr_hugepages=128

有趣的是，有人对门罗币挖矿产生的电量进行了初步预测，尽管预测曲线和实际状况在18年底并不一致，最终结果和能耗估算很接近。19年三月，门罗币再次硬分叉，其能耗曲线已经展现一定程度的规律性。
参考文献：
https://maijiaoben.com/centos-monero.html
https://bitinfocharts.com/comparison/monero-hashrate.html
https://www.sciencedirect.com/science/article/pii/S0360544218322503

The followings are just for practicing English.
An ECS with centos installed was rent while creating websites. Only two websites are running on it. CPU usage usually is 0%, and sometimes 40% at most. Leaving it unused is a waste. It is sad that CPU calculation can obtain Monero, so let’s do it.
The first step is to get a wallet address. There are two methods to get it, local registration and online registration. The later one is chosen, so the previous one is neglected here. There are many platforms, such as https://mymonero.com/, and https://hitbtc.com/. After registration, you need to copy the address, which will be used later.
Copy and paste the commands to install mining tool on the server:
yum install centos-release-scl cmake3 hwloc-devel libmicrohttpd-devel openssl-devel
yum install devtoolset-4-gcc*
scl enable devtoolset-4 bash
git clone https://github.com/fireice-uk/xmr-stak-cpu xmr-stak
cd xmr-stak
cmake3 .
make install
After installation, check the version by input: /usr/local/bin/cmake –version. The commands may vary depending on the versions. Then, modify “config.txt”, input your pool address, your wallet address, and your password ID based on the examples at line 109-111, and delete the “*” at line 25-29 approximately. Port 3333 is the easiest for low & mid-range CPUs.
After these, you can start mining by input the following commands:
cd /root/xmr-stak/bin/
./xmr-stak-cpu
However, I met the problem of MEMORY ALLOC FAILED: mmap failed. The solution is to stop mining and enter /etc/security/limits.conf, add the following lines in the end of the file:

soft memlock 262144

hard memlock 262144
Save and exit the file and input “sysctl -w vm.nr_hugepages=128”. Then, reboot.