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translating---geekpi
Find your systems easily on a LAN with mDNS
======
![](https://fedoramagazine.org/wp-content/uploads/2018/09/mDNS-816x345.jpg)
Multicast DNS, or mDNS, lets systems broadcast queries on a local network to find other resources by name. Fedora users often own multiple Linux systems on a router without sophisticated name services. In that case, mDNS lets you talk to your multiple systems by name — without touching the router in most cases. You also dont have to keep files like /etc/hosts in sync on all the local systems. This article shows you how to set it up.
mDNS is a zero-configuration networking service thats been around for quite a while. Fedora ships Avahi, a zero-configuration stack that includes mDNS, as part of Workstation. (mDNS is also part of Bonjour, found on Mac OS.)
This article assumes you have two systems running supported versions of Fedora (27 or 28). Their host names are meant to be castor and pollux.
### Installing packages
Make sure the nss-mdns and avahi packages are installed on your system. You might have a different version, which is fine:
```
$ rpm -q nss-mdns avahi
nss-mdns-0.14.1-1.fc28.x86_64
avahi-0.7-13.fc28.x86_64
```
Fedora Workstation provides both of these packages by default. If not present, install them:
```
$ sudo dnf install nss-mdns avahi
```
Make sure the avahi-daemon.service unit is enabled and running. Again, this is the default on Fedora Workstation.
```
$ sudo systemctl enable --now avahi-daemon.service
```
Although optional, you might also want to install the avahi-tools package. This package includes a number of handy utilities for checking how well the zero-configuration services on your system are working. Use this sudo command:
```
$ sudo dnf install avahi-tools
```
The /etc/nsswitch.conf file controls which services your system uses to resolve services, and in what order. You should see a line like this in that file:
```
hosts: files mdns4_minimal [NOTFOUND=return] dns myhostname
```
Notice the commands mdns4_minimal [NOTFOUND=return]. They tell your system to use the multicast DNS resolver to resolve a hostname to an IP address. Even if that service works, the remaining services are tried if the name doesnt resolve.
If you dont see a configuration similar to this, you can edit it (as the root user). However, the nss-mdns package handles this for you. Remove and reinstall that package to fix the file, if youre uncomfortable editing it yourself.
Follow the steps above for **both systems**.
### Setting host name and testing
Now that youve done the common configuration work, set up each hosts name in one of these ways:
1. If youre using Fedora Workstation, [you can use this procedure][1].
2. If not, use hostnamectl to do the honors. Do this for the first box:
```
$ hostnamectl set-hostname castor
```
3. You can also edit the /etc/avahi/avahi-daemon.conf file, remove the comment on the host-name setting line, and set the name there. By default, though, Avahi uses the system provided host name, so you **shouldnt** need this method.
Next, restart the Avahi daemon so it picks up changes:
```
$ sudo systemctl restart avahi-daemon.service
```
Then set your other box properly:
```
$ hostnamectl set-hostname pollux
$ sudo systemctl restart avahi-daemon.service
```
As long as your network router is not disallowing mDNS traffic, you should now be able to login to castor and ping the other box. You should use the default .local domain name so resolution works correctly:
```
$ ping pollux.local
PING pollux.local (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1 (192.168.0.1): icmp_seq=1 ttl=64 time=3.17 ms
64 bytes from 192.168.0.1 (192.168.0.1): icmp_seq=2 ttl=64 time=1.24 ms
...
```
The same trick should also work from pollux if you ping castor.local. Its much more convenient now to access your systems around the network!
Moreover, dont be surprised if your router advertises services. Modern WiFi and wired routers often provide these services to make life easier for consumers.
This process works for most systems. However, if you run into trouble, use avahi-browse and other tools from the avahi-tools package to see what services are available.
--------------------------------------------------------------------------------
via: https://fedoramagazine.org/find-systems-easily-lan-mdns/
作者:[Paul W. Frields][a]
选题:[lujun9972](https://github.com/lujun9972)
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译,[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://fedoramagazine.org/author/pfrields/
[1]: https://fedoramagazine.org/set-hostname-fedora/

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使用 mDNS 在局域网中轻松发现系统
======
![](https://fedoramagazine.org/wp-content/uploads/2018/09/mDNS-816x345.jpg)
多播 DNS 或 mDNS 允许系统通过在广播查询局域网中的其他资源。Fedora 用户经常在没有复杂名称服务的路由器上拥有多个 Linux 系统。在这种情况下mDNS 允许你按名称与多个系统通信 - 多数情况下不用路由器。你也不必在所有本地系统上同步类似 /etc/hosts 之类的文件。本文介绍如何设置它。
mDNS 是一个零配置网络服务它已经诞生了很长一段时间。Fedora 将 Avahi (包含 mDNS 的零配置系统)作为工作站的一部分。 mDNS 也是 Bonjour 的一部分,可在 Mac OS 上找到。)
本文假设你有两个系统运行受支持的 Fedora 版本27 或 28。它们的主机名是 castor 和 pollux。
### 安装包
确保系统上安装了 nss-mdns 和 avahi 软件包。你可能是不同的版本,这也没问题:
```
$ rpm -q nss-mdns avahi
nss-mdns-0.14.1-1.fc28.x86_64
avahi-0.7-13.fc28.x86_64
```
Fedora Workstation 默认提供这两个包。如果不存在,请安装它们:
```
$ sudo dnf install nss-mdns avahi
```
确保 avahi-daemon.service 单元已启用并正在运行。同样,这是 Fedora Workstation 的默认设置。
```
$ sudo systemctl enable --now avahi-daemon.service
```
虽然是可选的,但你可能还需要安装 avahi-tools 软件包。该软件包包括许多方便的程序,用于检查系统上的零配置服务的工作情况。使用这个 sudo 命令:
```
$ sudo dnf install avahi-tools
```
/etc/nsswitch.conf 控制系统使用哪个服务用于解析,以及它们的顺序。你应该在那个文件中看到这样的一行:
```
hosts: files mdns4_minimal [NOTFOUND=return] dns myhostname
```
注意命令 mdns4_minimal [NOTFOUND=return]。它们告诉你的系统使用多播 DNS 解析程序将主机名解析为 IP 地址。即使该服务有效,如果名称无法解析,也会尝试其余服务。
如果你没有看到与此类似的配置,则可以对其进行编辑(以 root 用户身份。但是nss-mdns 包会为你处理此问题。如果你对自己编辑它感到不舒服,请删除并重新安装该软件包以修复该文件。
在**两个系统**中执行同样的步骤 。
### 设置主机名并测试
现在你已完成常见的配置工作,请使用以下方法之一设置每个主机的名称:
1. 如果你正在使用 Fedora Workstation[你可以使用这个步骤][1]。
2. 如果没有,请使用 hostnamectl 来做。在第一台机器上这么做:
```
$ hostnamectl set-hostname castor
```
3. 你还可以编辑 /etc/avahi/avahi-daemon.conf删除主机名设置行上的注释并在那里设置名称。但是默认情况下Avahi 使用系统提供的主机名,因此你**不应该**需要此方法。
接下来,重启 Avahi 守护进程,以便它接收更改:
```
$ sudo systemctl restart avahi-daemon.service
```
然后正确设置另一台机器:
```
$ hostnamectl set-hostname pollux
$ sudo systemctl restart avahi-daemon.service
```
只要你的路由器没有禁止 mDNS 流量,你现在应该能够登录到 castor 并 ping 通另一台机器。你应该使用默认的 .local 域名,以便解析正常工作:
```
$ ping pollux.local
PING pollux.local (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1 (192.168.0.1): icmp_seq=1 ttl=64 time=3.17 ms
64 bytes from 192.168.0.1 (192.168.0.1): icmp_seq=2 ttl=64 time=1.24 ms
...
```
如果你在 pollux ping castor.local同样的技巧也适用 。现在在网络中访问你的系统更方便了!
此外,如果你的路由器宣传这个服务,请不要感到惊讶。现代 WiFi 和有线路由器通常提供这些服务,以使消费者的生活更轻松。
此过程适用于大多数系统。但是,如果遇到麻烦,请使用 avahi-browse 和 avahi-tools 软件包中的其他工具来查看可用的服务。
--------------------------------------------------------------------------------
via: https://fedoramagazine.org/find-systems-easily-lan-mdns/
作者:[Paul W. Frields][a]
选题:[lujun9972](https://github.com/lujun9972)
译者:[geekpi](https://github.com/geekpi)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译,[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://fedoramagazine.org/author/pfrields/
[1]: https://fedoramagazine.org/set-hostname-fedora/