樹莓派插入U盤自動拷貝系統日志到U盤或通過U盤升級程序
注意，U盤用Fat32格式，NTFS格式的話，需要在Linux另外安裝相應驅動。
可通過udev實現如題的功能。
在/etc/udev/rules.d/目錄下新建規則文件98-logcopy.rules
內容如下：
KERNEL!="sd[a-z][0-9]", GOTO="media_by_label_auto_mount_end" # Import FS infos IMPORT{program}="/sbin/blkid -o udev -p %N" # Get a label if present, otherwise specify one ENV{ID_FS_LABEL}!="", ENV{dir_name}="%E{ID_FS_LABEL}" ENV{ID_FS_LABEL}=="", ENV{dir_name}="usbhd-%k" # Global mount options ACTION=="add", ENV{mount_options}="relatime" # Filesystem-specific mount options ACTION=="add", ENV{ID_FS_TYPE}=="vfat|ntfs", ENV{mount_options}="$env{mount_options},utf8,gid=100,umask=002" # Mount the device ACTION=="add", RUN+="/bin/mkdir -p /media/%E{dir_name}", RUN+="/bin/mount -o $env{mount_options} /dev/%k /media/%E{dir_name}" RUN+="/bin/cp -r /opt/trash/logs /media/%E{dir_name}" # Clean up after removal ACTION=="remove", ENV{dir_name}!="", RUN+="/bin/umount -l /media/%E{dir_name}", RUN+="/bin/rmdir /media/%E{dir_name}" # Exit LABEL="media_by_label_auto_mount_end"
可根據實際情況，修改掛載后的處理腳本。
保存文件并重啟，插入U盤測試，發現并未成功的拷貝日志。
通過如下命令查看日志
systemctl status udev
看到有如下錯誤提示：
pi@raspberrypi:~ $ systemctl status udev
● systemd-udevd.service - udev Kernel Device Manager
Loaded: loaded (/lib/systemd/system/systemd-udevd.service; static; vendor preset: enabled)
Active: active (running) since Sat 2019-08-10 16:31:27 CST; 6h ago
Docs: man:systemd-udevd.service(8)
man:udev(7)
Main PID: 128 (systemd-udevd)
Status: "Processing with 16 children at max"
CGroup: /system.slice/systemd-udevd.service
└─128 /lib/systemd/systemd-udevd
Aug 10 21:27:15 raspberrypi mtp-probe[8780]: checking bus 1, device 8: "/sys/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.1/1-1.1.2"
Aug 10 21:27:17 raspberrypi systemd-udevd[8785]: Process '/root/mount_manager/mount_manager add' failed with exit code 1.
Aug 10 21:27:30 raspberrypi mtp-probe[8822]: checking bus 1, device 9: "/sys/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.3"
Aug 10 21:27:49 raspberrypi systemd-udevd[8871]: Process '/root/mount_manager/mount_manager remove' failed with exit code 1.
Aug 10 22:34:07 raspberrypi systemd-udevd[10802]: Process '/bin/umount -l /media/usbhd-sda1' failed with exit code 32.
Aug 10 22:34:07 raspberrypi systemd-udevd[10802]: Process '/bin/rmdir /media/usbhd-sda1' failed with exit code 1.
Aug 10 22:34:43 raspberrypi mtp-probe[10815]: checking bus 1, device 10: "/sys/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.1/1-1.1.2"
Aug 10 22:34:45 raspberrypi systemd-udevd[10819]: Process '/bin/mkdir -p /media/usbhd-sda1' failed with exit code 1.
Aug 10 22:34:45 raspberrypi systemd-udevd[10819]: Process '/bin/mount -o relatime,utf8,gid=100,umask=002 /dev/sda1 /media/usbhd-sda1' failed with exit code 32.
Aug 10 22:34:45 raspberrypi systemd-udevd[10819]: Process '/bin/cp /opt/trash/logs /media/usbhd-sda1' failed with exit code 1.
經過Google查詢，原來樹莓派的系統有點Bug。關于此問題的詳細信息 看這里
解決方法：
sudo nano /lib/systemd/system/systemd-udevd.service
打開上面的文件，將后7行注釋掉，就可以了。否則udev規則雖會觸發執行，但會執行失敗。
修改后的文件內容如下：
# This file is part of systemd. # # systemd is free software; you can redistribute it and/or modify it # under the terms of the GNU Lesser General Public License as published by # the Free Software Foundation; either version 2.1 of the License, or # (at your option) any later version. [Unit] Description=udev Kernel Device Manager Documentation=man:systemd-udevd.service(8) man:udev(7) DefaultDependencies=no Wants=systemd-udevd-control.socket systemd-udevd-kernel.socket After=systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-sysusers.service Before=sysinit.target ConditionPathIsReadWrite=/sys [Service] Type=notify OOMScoreAdjust=-1000 Sockets=systemd-udevd-control.socket systemd-udevd-kernel.socket Restart=always RestartSec=0 ExecStart=/lib/systemd/systemd-udevd #KillMode=mixed #WatchdogSec=3min #TasksMax=infinity #MountFlags=slave #MemoryDenyWriteExecute=yes #RestrictRealtime=yes #RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
再次保存，重啟。
將U盤插入樹莓派，已經成功復制了日志文件。
現在也還有不完善的地方，比如，設備如果有多套，往U盤拷貝日志的路徑是一樣的，那么永遠只能拿到最后插的那臺設備的日志。所以應該能在Copy日志的時候用與設備相關的名稱做為目錄對日志文件進行管理。
按如上設想修改后，就可以用一個U盤從現場取N個設備的日志了。
我又想到，也可以反方向的，像安卓手機卡刷一樣，用U盤升級系統。
===================================================================================================
2019-08-11更新 實現上面末尾提到的兩個功能
由板載程序在/opt/trash/boxid.txt位置創建一個保存設備編號的文件。板載程序通過登錄應答消息從服務端得到設備編號，并寫入到上述文件。
再把規則文件修改一下，掛載完U盤后執行一個Shell腳本，修改后內容如下：
KERNEL!="sd[a-z][0-9]", GOTO="media_by_label_auto_mount_end"
# Import FS infos
IMPORT{program}="/sbin/blkid -o udev -p %N"
# Get a label if present, otherwise specify one
ENV{ID_FS_LABEL}!="", ENV{dir_name}="%E{ID_FS_LABEL}"
ENV{ID_FS_LABEL}=="", ENV{dir_name}="usbhd-%k"
# Global mount options
ACTION=="add", ENV{mount_options}="relatime"
# Filesystem-specific mount options
ACTION=="add", ENV{ID_FS_TYPE}=="vfat|ntfs", ENV{mount_options}="$env{mount_options},utf8,gid=100,umask=002"
# Mount the device
ACTION=="add", RUN+="/bin/mkdir -p /media/%E{dir_name}", RUN+="/bin/mount -o $env{mount_options} /dev/%k /media/%E{dir_name}" RUN+="/opt/trash/usb %E{dir_name}"
# Clean up after removal
ACTION=="remove", ENV{dir_name}!="", RUN+="/bin/umount -l /media/%E{dir_name}", RUN+="/bin/rmdir /media/%E{dir_name}"
# Exit
LABEL="media_by_label_auto_mount_end"
在/opt/trash目錄下創建一個shell腳本，名稱為usb
shell腳本內容如下：
#!/bin/bash
boxid=$(cat /opt/trash/boxid.txt)
curdt=$(date +%Y%m%d%H%M%S)
sudo mkdir -p /media/$1/boxlogs/${boxid}/${curdt}
sudo cp -r /opt/trash/logs/* /media/$1/boxlogs/${boxid}/${curdt}
sudo cp /media/$1/boxupdate/* /opt/trash
以上腳本先從/opt/trash/boxid.txt文件取得保存的設備編號，然后又取了當前時間，按“設備號/時間”的形式創建了目錄，然后再把日志拷貝到這個目錄里。
最后一句是從U盤指定目錄拷貝內容到板載程序目錄，實現了用U盤更新板載程序的功能。
這樣，功能就完美了。
附幾個命令：
udevadm monitor sudo udevadm control --reload-rules
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