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Questions[devices](server)

Martin Hope
sanosuke_kursch
Asked: 2021-09-12 08:38:03 +0800 CST
  • 4

So, I've been looking into this systemd "Predictable Network Interface Names" for quite some time and got some understanding on how it works, but I can't for the love of Thor figure out the naming scheme with enpXsY, I know that it's supposed to indicate the physical location of the device, but what exactly does the X and Y mean? Which one is the physical location? What exactly does the other indicate, a bus index, perhaps? I have no idea and really want to know. I searched high and low and could find nothing explaining in detail how this naming scheme works.

networking pci systemd devices
Martin Hope
Some Name
Asked: 2021-06-10 15:43:36 +0800 CST
  • 2

I'm new to QEMU and playing around with its chardevs. I faced the option called -chardev pty,id=id. So I tried to create a VM with -chardev pty,id=pty0 and got the message.

char device redirected to /dev/pts/9 (label pty0)

So I tried to send some data to it:

root@super-pc:~# cat /dev/pts/9

and didn't see any output.

What is the use case of this chardev?

linux kvm-virtualization qemu devices
Martin Hope
Mathias Begert
Asked: 2016-09-16 14:12:40 +0800 CST
  • 32

I am preparing for a certification and have a locally installed CentOS7 (VirtualBox) and another instance in a cloud-based service.

On the local system I have a /dev/sda and on the cloud-based i have a /dev/vda.

Now I am wondering what this difference exactly means? Is there a standard (documentation?) for the naming of this devices, and what the different names stand for?

Edit:

I think this document is very useful to understand the naming: https://www.kernel.org/doc/Documentation/admin-guide/devices.txt

8 block SCSI disk devices (0-15)
      0 = /dev/sda      First SCSI disk whole disk
     16 = /dev/sdb      Second SCSI disk whole disk
     32 = /dev/sdc      Third SCSI disk whole disk
        ...
    240 = /dev/sdp      Sixteenth SCSI disk whole disk

But I could not find some information about /dev/vda.

virtualization devices
Martin Hope
user544955
Asked: 2012-05-23 06:25:18 +0800 CST
  • 4

I've just 'inherited' a system that consists of a bunch of Linux servers (running Ubuntu, but probably not important) that uses iSCSI devices. These show up as /dev/sdb, /dev/sdc etc. when you log them in using the iscsiadm command.

However, the way that these devices have had filesystems formatted on them is not something I've done before, although I have heard of it. The filesystems (ext4 in this case) have been formatted directly on them, so a mkfs /dev/sdb command was probably issued. In the past I have always created partition(s) on a device using fdisk or parted, /dev/sdb1 etc., and formatted my filesystems on the partition.

Has anyone ever seen filesystems formatted directly on a device with no partitioning before and would you recommend it? Are there any reasons you might strongly argue against doing things that way?

Thanks,

linux partition filesystems devices
Martin Hope
user626201
Asked: 2011-05-04 04:00:03 +0800 CST
  • 11

Our Linux kernel is 2.6.31 running on an embedded MIPS processor with busybox.

The initialisation script (rcS) starts mdev with:

echo "/sbin/stbhotplug" > /proc/sys/kernel/hotplug
mdev -s

Can anyone tell me what the Linux utility mdev does?

It looks like it does auto hot plugging as the stbhotplug is a script that handle ethernet interfaces.

Also, the rootfs we have been given only has a console device i.e. /dev/console is the only file in /dev.

However, when the system is running, the /dev directory is full of device files (e.g. /dev/mtd, etc.).

The reason I ask is that occasionally we get an error whereby it is reported that /dev/ubi_ctrl is not found or /dev/ubi1 is not found.

How or when does Linux create these devices?

Thanks.

linux linux-kernel rootfs devices embedded-linux