From Dynamic to Static IP Address on CentOS 7

Get the current network status related on some Network Interface (ex: ens192):

Now we get some important information:

• 192.168.109.56/23 => IP 192.168.109.56 & MASK 255.255.254.0
  
• GATEWAY=192.168.109.254
  

We keep all the settings except "dynamic", in /etc/sysconfig/network-scripts/ifcfg-ens192:

• ONBOOT=yes
• NM_CONTROLLED=no
• BOOTPROTO=static
• IPADDR=192.168.109.56
• NETMASK=255.255.254.0
• GATEWAY=192.168.109.254
  

After configuration saved, restart network service and verify:

• service network restart
• ip a show ens192
  

NFS on CentOS 7

•  Server Side (server.nfs.net)
  
• install
• yum install nfs-utils
• share /var/share
• mkdir /var/share
• chmod 755 /var/share
• chown nfsnobody:nfsnobody /var/share
• service
• systemctl start rpcbind
• systemctl start nfs-server
• systemctl enable rpcbind
• systemctl enable nfs-server
• vi /etc/exports
  
• /var/share *(ro,wdelay)
• /var/share client.nfs.net(rw,sync)
  
• restart
• systemctl restart nfs-server
• firewall
• firewall-cmd --permanent --add-service=nfs
• firewall-cmd --permanent --add-service=mountd
• firewall-cmd --permanent --add-service=rpc-bind
• firewall-cmd --reload
• Client Side (client.nfs.net)
  
• install
• yum install nfs-utils
• share mapping
• mkdir -p /mnt/nfs/var/share
• mount -t nfs server.nfs.net:/var/share /mnt/nfs/var/share
• vi /etc/fstab (optional, auto mount after reboot)
• server.nfs.net:/var/share /mnt/nfs/var/share nfs defaults 0 0
  

Building private and cheaper ngrok-like tunnels

• In mrvm.net, you can cost USD$4 / year for 1 IPv4 address and 20 ports. In my case, 198.204.227.x 21001 ~ 21020.
• The ssh for mrvm.net is using another port. So you can control your VPS like ssh user@198.204.227.x -p 21021.
• In noip.com, you can register 3 free domain names like abc.hopto.org or xyz.ddns.net.
• Using inlets, you can expose your intranet service on the cloud:
• VPS
• export token=$(head -c 16 /dev/urandom | sha1sum | cut -d" " -f1)
• inlets server --port=21001 --token=$token
• DEV
• python -m SimpleHTTPServer 8000 (or your service)
• inlets client --remote=abc.hopto.org:21001 --upstream=http://localhost:8000 --token=...
• Client
• curl http://abc.hopto.org:21001

Install Appium on CentOS 7

• Refer this guide, install Node.js and npm.
• If you following this guide immediately, Appium install will fail caused by EACCES. So refer this guide for reinstall nvm forcibly.
• Relogin.
• Reinstall npm and Node.js by nvm, command: "nvm install node".
• Now you can install Appium without error.

New Selenium Node (Chrome / Firefox) on CentOS without GUI

• Assume Selenium Hub listen on docker host 172.17.0.1:4444
• docker (refer this)
• docker-compose (refer this)
• docker-compose.yml (updated from here)
• version: "3"
• services:
• chrome:
• image: selenium/node-chrome:3.141.59-neon
• volumes:
• - /dev/shm:/dev/shm
• environment:
• - HUB_HOST=172.17.0.1
• - HUB_PORT=4444
• - REMOTE_HOST=http://<Host_or_IP>:6666
• - NODE_MAX_INSTANCES=5
• ports:
• - "6666:5555"
• firefox:
• image: selenium/node-firefox:3.141.59-neon
• volumes:
• - /dev/shm:/dev/shm
• environment:
• - HUB_HOST=172.17.0.1
• - HUB_PORT=4444
• - REMOTE_HOST=http://<Host_or_IP>:7777
• - NODE_MAX_INSTANCES=5
• ports:
• - "7777:5555"

Quick Start: Selenium Grid

How can we create a Selenium Grid Environment quickly? If you have docker-compose already, just refer this, save as docker-compose.yml, and run "docker-compose up -d" to start it. That's all.

How to prove it worked? we need:

• selenese-runner.jar download from here
• check your docker host ip address like "ip addr | grep docker0"
• any workable side file

If selenese-runner.jar and my.side in the current directory, start another docker container:

• docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp openjdk java -jar selenese-runner.jar --driver remote --remote-url http://<DOCKER_HOST_IP>:4444/wd/hub --remote-browser <BROWSER> <WORKABLE.side>

<BROWSER> can be chrome or firefox.

CentOS7, Firewalld and Docker

In the past, I always stop firewalld for Docker. But it's not secured. According to this, if we update firewalld version to 0.4.3.2-9 can fix this, or running these command:

• nmcli connection modify docker0 connection.zone trusted
• systemctl stop NetworkManager.service
• firewall-cmd --permanent --zone=trusted --change-interface=docker0
• systemctl start NetworkManager.service
• nmcli connection modify docker0 connection.zone trusted
• systemctl restart docker.service

Docker & Docker Compose on CentOS

• Docker
• sudo yum install yum-utils
• sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
• sudo yum install docker-ce
• sudo systemctl start docker
• (optional) sudo systemctl enable docker
• sudo usermod -aG docker `whoami`
• (logout, then login again)
• (optional) docker ps
• Docker Compose
• (docker installed)
• (check latest version of Docker Compose from here, ex: 1.23.2)
• sudo curl -L “https://github.com/docker/compose/releases/download/1.23.2/docker-compose-$(uname -s)-$(uname -m)” -o /usr/local/bin/docker-compose
• sudo chmod +x /usr/local/bin/docker-compose
• (optional) docker-compose --version

offline install yum package - MariaDB

以安裝 MariaDB 為例，由於 CentOS YUM repository 並沒有最新版，要自己上 Maria 官網看這個說明下載，常做也是有點麻煩。這次希望準備一個「離線版」安裝包，既不用等網路，又可減少安裝程序。首先參考這篇的前置動作，下載與目錄準備：

• sudo yum install yum-plugin-downloadonly yum-utils createrepo
• mkdir /var/tmp/maria
• mkdir /var/tmp/maria-installroot

再來是準備 /etc/yum.repos.d/mariadb.repo，內容如下：

• [mariadb]
• name = MariaDB
• baseurl = http://yum.mariadb.org/10.3/centos7-amd64
• gpgkey = https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
• gpgcheck = 1

接著把 yum maria 下載安裝分開，下載是：

• sudo yum install --downloadonly --installroot=/var/tmp/maria-installroot --releasever=7 --downloaddir=/var/tmp/maria MariaDB-server MariaDB-client
• sudo curl https://yum.mariadb.org/RPM-GPG-KEY-MariaDB -o /etc/pki/rpm-gpg/RPM-GPG-KEY-MariaDB

包裹成離線安裝資源：

• createrepo --database /var/tmp/maria
• sudo rm -rf /var/tmp/maria-installroot

再準備「離線版」/etc/yum.repos.d/mariadb-offline.repo：

• [mariadb-offline]
• name = MariaDB-offline
• baseurl = file:///var/tmp/maria
• enabled = 0
• checkgpg = 1
• gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7 file:///etc/pki/rpm-gpg/RPM-GPG-KEY-MariaDB

可以多檢查一下完整性：

• repoclosure --repoid=mariadb-offline

如果沒問題的話，把 /var/tmp/maria 目錄壓成一個檔案：

• tar -cvf mariadb-offline.tar /var/tmp/maria

未來就解壓 mariadb-offline.tar，以及 /etc/yum.repos.d/mariadb-offline.repo /etc/pki/rpm-gpg/RPM-GPG-KEY-MariaDB 搬到要安裝 MariaDB 的 CentOS 7 主機上，即使對外無網路，也可以順利安裝 MariaDB：

• tar -xvf mariadb-offline.tar -C /
• sudo yum --disablerepo=\* --enablerepo=mariadb-offline install MariaDB-server MariaDB-client

安裝後再人工啟動：

• systemctl start mariadb

[2018/08/09]
java-1.8.0-openjdk 類似的過程：雖然官方 yum 有收此套件，省了多一組 GPG-KEY 的問題，但可能另外遇到目標主機沒有經過 yum update，以致 nss 比 openjdk 所需版本要舊。解決之道二選一：

• 出貨端要求各被安裝系統需求為「近日曾做過 yum update」，而且每次出貨前都先 yum update 再包離線安裝檔。（顯然是個爛方法）
• 離線安裝包增加 nss nss-tools（如果有需要的話，可能也要納入更多版本不符的套件），並且在安裝時額外指定一併安裝 nss 套件。

Auto sync CentOS server time

要讓眾 Client 向 Server 對時已是很多系統的基本需求，所以我們得先搞懂 Server 如何讓自己的時間準確？

• yum install ntp
• 根據這個網站挑選合適的時間伺服器列表，ping 確認網路通暢後，加在 /etc/ntp.conf
• systemctl start ntpd
• systemctl enable ntpd
• timedatectl set-ntp true
• 等五分鐘

以前不知要有點耐心，下完指令總以為還缺什麼，就是沒有校正時間？「等五分鐘」值得一記。