# Netconsole (简体中文)

netconsole 是一个通过网络发送所有内核日志消息（即dmesg）到另一台计算机的内核模块，且无需用户空间（如syslogd的）。 "netconsole" 这个名字不是很恰当，因为它不是一个真正的“控制台”，更像是一个远程日志服务。

它可以内建或者编译成模块使用.内建式的netconsole在网卡后立即初始化以尽快建立指定的接口. 模块方式一般用于获取无屏幕系统或用户空间无法工作时的 kernel panic 输出

文档位于内核代码当中：Documentation/networking/netconsole.txt

## 发送器配置

Install gnu-netcat from the official repositories.

### 内建配置

Netconsole and other modules' Kernel parameters can be passed from a bootloader to kernel at its startup via kernel command line by modifying the bootloader environment, which is type and version specific. Example for Uboot, where 1st address is Plug Computer ArchLinux device's netconsole Out Port & IP, and 2nd address is your PC's netconsole In Port & IP & adapter MAC:

    fw_setenv usb_custom_params 'loglevel=7 netconsole=6666@192.168.1.28/eth0,6666@192.168.1.19/00:13:32:20:r9:a5'

Logging is done by your ArchLinux set logger like syslog-ng, so available loglevels (output details) are defined in that logger docs, and may differ for each log type. One can also pass netconsole string parameters at kernel runtime (no config file required), then start two netconsole instances on the monitoring PC (one to read output, another for input), and restart it on the PC or device you are logging as shown in Dynamic Configuration:

    # set log level for kernel messages
    dmesg -n 8

    netconsole=6666@192.168.1.28/eth0,6666@192.168.1.19/00:13:32:20:r9:a5

    nc -l -u -p 6666 &
    nc -u 192.168.1.28 6666

One may need to switch off PC and router firewall, and setup proper router port forwarding to monitor and input data in Netconsole.

### 运行时配置

Netconsole can be loaded as one of kernel modules manually after boot or auto during boot depending on this module config. See kernel modules for configuring it to load at boot. For loading manually any time after boot:

    # set log level for kernel messages
    dmesg -n 8

    modprobe configfs
    modprobe netconsole
    mount none -t configfs /sys/kernel/config

    # 'netconsole' dir is auto created if the module is loaded
    mkdir /sys/kernel/config/netconsole/target1
    cd /sys/kernel/config/netconsole/target1

    # set local IP address
    echo 192.168.0.111 > local_ip
    # set destination IP address
    echo 192.168.0.17 > remote_ip
    # find destination MAC address
    arping `cat remote_ip` -f |grep -o ..:..:..:..:..:.. > remote_mac

    echo 1 > enabled

netconsole should now be configured. To verify, run 'dmesg |tail' and you should see "netconsole: network logging started". Check available log levels by running 'dmesg -h'.

## 接收器配置

    nc -u -l 6666

or

    nc -u -l -p 6666

## 引导时启动

只需将 netconsole 添加到内核引导命令行即可。内核按下列格式读取 "netconsole" 字符串参数：

      netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
            src-port      source for UDP packets (defaults to 6665)
            src-ip        source IP to use (interface address)
            dev           network interface (eth0)
            tgt-port      port for logging agent (6666)
            tgt-ip        IP address for logging agent
            tgt-macaddr   ethernet MAC address for logging agent (broadcast)

例如：

    linux /vmlinuz-linux root=UUID=a322511e-b028-4f11-87b6-e48b5d99bbd8 ro netconsole=514@10.0.0.1/eth1,514@10.0.0.2/12:34:56:78:9a:bc
    linux /vmlinuz-linux root=/dev/disk/by-label/ROOT ro netconsole=514@10.0.0.2/12:34:56:78:9a:bc

引自： Net Console for Boot Debugging[broken link: invalid section].

Categories:

- Kernel (简体中文)
- Networking (简体中文)

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