注意：是centos7才能用此方法
Step 1. First, you need to enable EPEL repository on your system.
yum install epel-release
yum -y update
Step 2. Installing Transmission.
Just run the following command to install Transmission:
yum install transmission-cli transmission-common transmission-daemon
Once complete, you can verify Transmission is installed by running the below command:
systemctl start transmission-daemon.service
systemctl stop transmission-daemon.service
Step 3. Configuration Transmission.
Edit the transmission settings.json config file:
yum install nano
nano /var/lib/transmission/.config/transmission-daemon/settings.json
OK now let’s edit the settings (to your liking) and don’t forget to save.
"rpc-authentication-required": true,
"rpc-enabled": true,
"rpc-password": "mypassword",
"rpc-username": "mysuperlogin",
"rpc-whitelist-enabled": false,
"rpc-whitelist": "0.0.0.0",
nano使用快捷Ctrl+X，然后会提示输入Y保存修改、输入N放弃修改，有的linux系统可能还要 回车（Enter) 确认。
After editing and saving the settings.json file, start the transmission daemon:
systemctl start transmission-daemon.service
Step 4. Accessing Transmission.
Transmission BitTorrent Client will be available on HTTP port 9091 by default. Open your favorite browser and navigate to http://yourdomain.com:9091 or http://server-ip:9091. You should be greeted with the Transmission WebUI. After logging in, you will notice that the value for the rpc-password inside the settings.json file will be hashed. If you are using a firewall, please open port 80 to enable access to the control panel.
Step 5.Transmission 自动启动
1.修改脚本文件rc.local：vim /etc/rc.d/rc.local
这个脚本是使用者自定的开机启动程序，可以在里面添加想在系统启动之后执行的脚本或者脚本执行命令
2.添加如下内容：
systemctl start transmission-daemon.service
3.esc 退出编辑，:wq 保存修改
4.将rc.local修改为可执行
chmod 777 /etc/rc.d/rc.local
Step 6.给Transmission下载目录授权读写权限
比如：775 权限
trouble shooting
在客户端访问服务端的 9091 端口打不开
检查 firewalld 是否启动，需要检查 tcp 9091 端口是否放行。注意 transmission 需要在一个端口（默认51413）监听，必须在 firewalld 中放行 tcp、udp 的这个端口。
sudo firewall-cmd --permanent --add-service=transmission-client,
这个 transmission-client 估计是在安装 transmission 的时候自动创建的。
检查本机的 9091 端口是否在 listening ss -lnp | grep 9091
修改下载路径到 /home/red/transmission
- add red to the transmission group
sudo usermod -a -G transmission red
- change the folder ownership
sudo chgrp -R transmission /home/red/transmission/
- grant write access to the group
sudo chmod -R 770 /home/red/transmission/
- Stop the deamon with
sudo systemctl stop transmission-daemon.service
The last thing to do is change the file creation mask, so that the downloaded files would be writeable by red.
sudo vim /var/lib/transmission/.config/transmission-daemon/settings.json
and change "umask": 18 to "umask": 2.
start tranmission-daemon
sudo sudo systemctl start transmission-daemon.service
修改 setting.json 设置默认下载路径
修改下面两个地方 修改配置需要提前 stop transmission-daemon
"download-dir": "/home/red/transmission",
"incomplete-dir": "/home/red/transmission",
如果要卸载transmission,请用命令：
yum erase transmission -y
centos6 安装transmission
安装后，启动transmission,然后再关掉：
service transmission-daemon start
service transmission-daemon stop
另外在CentOS 6上发现就算是修改了配置文件settings.json后启动transmission还行直接进入界面，根本不需要密码。
查看配置文件发"rpc-authentication-required": 又变成false，后来研究了好久发现还需要把/etc/init.d/transmission-daemon里面的参数修改一下
vi /etc/init.d/transmission-daemon
把
DAEMON_ARGS="-T --blocklist -g $TRANSMISSION_HOME/.config/transmission"
修改为
DAEMON_ARGS="-t --blocklist -g $TRANSMISSION_HOME/.config/transmission"
另外还要关闭transmission后再去修改settings.json，
service transmission-daemon stop
vi /var/lib/transmission/.config/transmission/settings.json把 "rpc-authentication-required": false,
修改为:"rpc-authentication-required": true,
启动 service transmission-daemon start