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kenn
Asked: 2016-11-08 01:58:56 +0800 CST

how to create a udev rule for usb flash with two partitions to create persistent node under /dev?

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I have a USB flash memory, I created two partitions on it, when it is attached sometimes it takes sda , sda1 and sda4 instead of sdb, sdb1, sdb4. To prevent that confusion I decided to create a udev rule to symlink it under /dev persistently.

I created the below rule

ACTION=="add", SUBSYSTEM=="usb", ATTRS{idVendor}=="0461", ATTRS{idProduct}=="4d81", SYMLINK+="myusb"

When I reboot it creates symlink under /dev/myusb but I can not mount it.

 sudo mount /dev/myusb /media/myusb

 mount: /dev/bus/usb/002/003 is not a block device

I think I get that error because it contains two partitions. So what shoul I do?

usb

2 Answers

  1. I think the problem is that you cannot mount a whole drive with several partitions at once. You have to mount each partition for itself. Mounting means getting access to the filesystem, which can be very different on two different partitions. And how would you put two filesystems into one directory? You have to have at least two subdirectories like /media/myusb/part1.

    That said we are back to UUIDs and labels.

    You could create an udev rule triggering a script that mounts the two partitions by their uuid, like

    #!/bin/bash

mount /dev/disk/by-uuid/xxxxx-xxxx-xxxxx-xxxxxx /media/myusb/part1
mount /dev/disk/by-uuid/yyyyy-yyyy-yyyyyy-yyyyy /media/myusb/part2

    Alternatively you could place the partitions into /etc/fstab, and let udev do a mount -a .

    Use 'blkid' to print the universally unique identifier for a device; this may be used with UUID= as a more robust way to name devices that works even if disks are added and removed.

    Maybe you could try that:

    For partition one:

    KERNEL=="sd?1", SUBSYSTEMS=="usb", ATTRS{idVendor}=="0461", ATTRS{idProduct}=="4d81", SYMLINK+="myusb1"

    For partition two

    KERNEL=="sd?4", SUBSYSTEMS=="usb", ATTRS{idVendor}=="0461", ATTRS{idProduct}=="4d81", SYMLINK+="myusb2"

    Not sure if it works, but you could give it a try.

    https://oracle-base.com/articles/linux/udev-scsi-rules-configuration-in-oracle-linux https://wiki.ubuntuusers.de/udev/

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  2. First of all I want to thank all who responded, they guided me on the right path.

    At first I checked out devices to locate usb stick

     fdisk -l 

Disk /dev/sda: 15.5 GB, 15512174592 bytes
234 heads, 12 sectors/track, 10789 cylinders, total 30297216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00055ec3

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *       16128    30297215    15140544    c  W95 FAT32 (LBA)
/dev/sda4         2142880     5194399     1525760    0  Empty

Disk /dev/sdb: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000517fa

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb2   *        2048    40959079    20478516   83  Linux
/dev/sdb3        40959998   234436544    96738273+   5  Extended
/dev/sdb5        40960000    52956093     5998047   83  Linux
/dev/sdb6        52957184   221904895    84473856   83  Linux
/dev/sdb7       221906944   234436544     6264800+  83  Linux

    My usb stick grabbed sda sda1 and sda4 (I haven't found a way to assign sda to primary disk yet)

    Then I did an attribute-walk to get related parameters with 

    udevadm info -a -p $(udevadm info -q path -n /dev/sda)
udevadm info -a -p $(udevadm info -q path -n /dev/sda1)
udevadm info -a -p $(udevadm info -q path -n /dev/sda4)

    I used ATTRS{serial} and ATTR{partition}==1, ATTR{partition}==2 as distinguishing IDs.

    KERNEL=="sd*", ATTRS{serial}=="0019E06B5883CCA187BC2C59", ATTR{partition}=="1", SYMLINK+="usbdevices"

    works for partition 1

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