Re: [gentoo-user] Rename /dev/nvme0n1 to /dev/sda

[Mike Gilbert]

On Mon, Sep 4, 2017 at 11:00 AM, Grant <emailgrant@×××××.com> wrote:
>>>>>>> My new laptop uses /dev/nvme0n1 instead of /dev/sda which conflicts
>>>>>>> with the script I use to manage about 12 similar laptops running
>>>>>>> Gentoo.  Is there a udev method for renaming the disk that will work
>>>>>>> well with any USB disks that happen to also be attached?
>>>>>>
>>>>>> I'm not certain what you mean by that, but I would guess that you want
>>>>>> the nvme disk to show up as /dev/sda, and the USB disk(s) to show up
>>>>>> as /dev/sd[b-z].
>>>>>>
>>>>>> It is not possible to accomplish this using udev; the kernel owns the
>>>>>> /dev/sdX device namespace, and will sequentially create devices nodes
>>>>>> for SCSI-like block devices using that namespace. There is no way to
>>>>>> change that using a udev rule.
>>>>>
>>>>>
>>>>> Can I rename /dev/sda to /dev/sd[b-z] if it's attached via USB, and
>>>>> then rename /dev/nvme0n1 to /dev/sda if /dev/nvme0n1 exists?
>>>>>
>>>>> Alternatively, can I rename /dev/sda to /dev/sd[b-z] if /dev/sda and
>>>>> /dev/nvme0n1 exist, and then rename /dev/nvme0n1 to /dev/sda if
>>>>> /dev/nvme0n1 exists?
>>>>
>>>> You might technically be able to do it, but I would guess it would
>>>> cause some nasty race conditions between the kernel and udev. It's a
>>>> bad idea.
>>>
>>>
>>> Is it the conditionals that cause this to be a bad idea?  Because I
>>> believe udev has functionality designed to rename devices exactly like
>>> this.
>>
>> udev doesn't provide any functionality to rename device nodes. You can
>> adjust their permissions, and create symlinks, but there is no direct
>> way to rename them.
>
>
> I use stuff like this to rename my USB devices and it works perfectly:
>
> SUBSYSTEM=="net", ACTION=="add", ENV{ID_NET_NAME_PATH}=="enp0s20u2u1",
> NAME="net0"
>
> Isn't this a true rename of the device node?

Network devices don't have device nodes. They have interface names,
which are a different concept entirely.