Questions tagged [devices]

devices refers to questions about the Unix/Linux device special files, normally these are under /dev. Do not use this tag for physical devices (for that use e.g. usb or pci).

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233 views

How do I mount USB CDROM Drive

I have an external usb cdrom drive but cannot find it in RHEL 7.4. The attached image is the results of my "ls /dev/". When I execute the "cat /var/log/dmesg | grep usb" I get the below results but ...
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2answers
759 views

What are all those 'sd' devices in /proc/devices

The /proc/devices file lists devices by major revision number and name. On my system it shows (partially): Block devices: 259 blkext 7 loop 8 sd 9 md 11 sr 65 sd 66 sd 67 sd 68 sd 69 sd ...
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Booting from Puppy Linux USB cannot see sda1

I am booting from a Puppy Linux USB Flash drive so that I can tar the primary partition of the hard drive. I see sda2 through to sda15, sdb1 to 15 (sdb1 is USB boot disk), sdc1 to 15, sdd1 to 15, sde1 ...
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143 views

Is it possible to use a pseudoterminal to redirect PPP’s dataflow to an application?

I want to set PPP in order to use a pseudoterminal slave (/dev/pts/N) instead of a physical serial link, handle its data flow in an application (from /dev/ptmx) and redirect that flow … somewhere ...
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1answer
260 views

Why does kpartx use a new loop device each time?

I'm running kpartx from within a python script as part of a custom OS build I'm trying to do. I'm using python sh module to run bash commands. sh.kpartx("-as", image) is how I attach my image. Then ...
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2answers
4k views

how to include or add /dev with tar --one-file-system

I'm running tar on a complete remote filesystem using ssh -n <hostname> 'sudo tar -cpvzf - --one-file-system /' | cat > Bak.tar.gz This gave me a tarball. I tried importing this tarball ...
7
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1answer
3k views

Writing raw images safely to USB sticks

Trying lots of different Linux distributions on all kinds of hardware, I find myself typing commands like this quite often: sudo dd if=xubuntu-13.10-desktop-amd64.iso of=/dev/sdc bs=10240 Needless ...
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1answer
3k views

Why does my USB device not appear on /dev?

We have a customized Linux distro (created via buildroot) running on an embedded platform. There's this relay module we need to connect to it through an USB port (the module is based on an ATmega32U2 ...
2
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1answer
300 views

Format of hiddev bytes?

I have a gamma spectrometer that connects as a USB HID. When it is inserted dmesg helpfully informs me that two device files were made for it, hiddev0 and hidraw2 (obviously, the numbering isn't ...
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1answer
162 views

How to mount 192.168.0.3:/dev/sda to local:/mnt/sda for cryptsetup luksOpen /mnt/sda?

as mentioned above, I have a cryptsetup full disk encrypted device on /dev/sda at 192.168.0.3. And I am at 192.168.0.2. $ sudo cryptsetup luksOpen user@192.168.0.3:/dev/sda encHDD $ sudo mount /dev/...
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337 views

why is it necessary to differentiate between character and block devices? [duplicate]

I have been trying to read the source code for linux. I started watching a Youtube video which mentioned that character and block devices are different. It didn't say much about why it matters because ...
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134 views

Mounting external hard drive makes all new files or pasted files with 777 permissions, how to change that?

I've looked all over and I can't find the answer to fix this. I also recognize I may not know the exact terms to use to search for this issue. So, I automount my external hard drive using: udisksct1 ...
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3answers
3k views

What happens if you delete a device file?

I roughly know about the files located under /dev. I know there are two types (character/block), accessing these files communicates with a driver in the kernel. I want to know what happens if I ...
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1answer
4k views

A Start Job is running for dev-md1.device

Hello everyone I'm with the following error on my CentOS 7 I restarted the server is now the boot time is with this message is already so minimum 40 minutes, what should I do? Please Help-me?
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1answer
810 views

Does the kernel delete entries in /dev on an initramfs?

I have a fully custom, minimal, embedded Linux (vanilla, 3.3.8, i486, Vortex86dx) system that boots from an initramfs image. No standard distribution scripts are used, just a single rcS file that does ...
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2answers
17k views

Difference between Device file and device drivers

I am beginner in device driver programming. I don't get the difference between device drivers and device files in Linux. Can anyone explain the difference?
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1answer
524 views

how to know if disks are from Jbod or integral as part of the HW machine

In some cases when we are not near the HW Linux machine, we are only able to see disks as the following: /dev/sdd 20511312 199536 20295392 1% /grd/sdd /dev/sdb ...
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2answers
18k views

ttyUSB0 permission changes after restart

I'm trying to install a device. I plug in the device which creates a ttyUSB0 file. When I open it in the program I need it for, it says the permission is denied. I type in terminal sudo chmod 666 /...
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4answers
35k views

How can I tell whether a network interface is physical (device) or virtual (alias)?

I have a small home router running OpenWrt (Kind of embedded Linux for routers). It has five Ethernet ports, one labeled WAN and four labeld LAN 1 to 4. It has the following Network Interfaces defined ...
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1answer
803 views

Slackware64 14.2 - GRUB2 - How set default <UUID> instead <DEVICE>?

i am trying the grub configuration file "/boot/grub/grub.cfg" in the kernel line, set "root=UUID=" instead "root=/dev/" for example when i ran : grub-mkconfig -o /boot/grub/grub.cfg the file /boot/...
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441 views

Accessing I2C slave devices that are specified in Device Tree

I'm trying to communicate with a device over I2C from my BeagleBone Black, and I'm a bit curious as to the device tree's interpretation of I2C. I see that there are a couple of device nodes within ...
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3answers
30k views

How to grant non-root user access to device files

I have device file that appears in /dev when a specific board is plugged in. The read and write operations to it work just fine, but in order to open the device file the program needs to be executed ...
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2answers
24k views

Allow non-root user to read/write /dev files

In my /dev folder, I would like the following files to be user readable and writable: /dev/ttyUSB0 /dev/gpib0 How do I do this without using chgrp? I can edit /etc/udev/rules.d but I do not know the ...
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3answers
35k views

How do I find out which process is using my V4L2 webcam?

I tried to run the following: $ vlc -I dummy v4l2:///dev/video0 --video-filter scene --no-audio --scene-path webcam.png --scene-prefix image_prefix --scene-format png vlc://quit --run-time=1 ...
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0answers
982 views

USB touch screen not working with debian 3.8.13 (BeagleBone Black)

I have a waveshare 7" HDMI touch screen display rev 2.1(touch over USB port and HDMI display) (link for the product) and I want to interface it with BeagleBone Black. The manufacturer says the 7" ...
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1answer
614 views

PCI Device Missing After Reboot

I have a DVBSky T9580 PCI tuner card. My problem is that after rebooting,, the device dissapears, lspci does not list it any more. I tried rebooting with reboot command as well as shutdown -r 0. ...
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1answer
98 views

Use /dev/ramX as their corresponding special devices?

With ls -l, I found a series of devices like ram0, ram1 etc. I looked at the output closely and (for example) brw------- 1 root root 1, 3 Jan 6 11:34 /dev/ram3 crw-rw-rw- 1 root root 1, 3 Jul 15 ...
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1answer
315 views

Identify devices like virtio2 and virtio3 in QEmu

I'm running a virtual machine in QEmu. The following command in the guest VM cat /proc/interrupts | egrep 'virtio.*(input|output)' gives me the following output: 26: 0 3376 0 ...
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1answer
2k views

Is it possible to simulate/force/fake an USB device unplug and replug on Linux?

So I've got a strange problem that I've been running onto. I've got a bitcoin usb miner, Bitfury, and I'm using CGMiner to mine. When I start the application, as root, the USB device is not detected ...
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1answer
184 views

Linux: How to create and attach a RamDisk without mounting it?

On Linux, how can a RAM disk be created and attached without being mounted? Moreover, how can the device name like /dev/sdb assigned to the RAM disk be found? Finally, how can the RAM disk (which is ...
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1answer
850 views

How to write to a character special device?

Due to a broken udev setup on a machine from which I'm trying to rescue data (see this post of mine) I'm trying to write to a "character special" device corresponding to a USB flash drive, but am ...
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1answer
1k views

Where to get information on failed disk?

I have a disk inside my server which has failed and I'm trying to figure out which one it is. I did not make a list of all serial numbers as I should have. I plan on doing this but in the meantime, ...
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2answers
92 views

OpenSuse USB HDD gets device node name “/dev/sdb” of internal HDD

OS: OpenSuse Leap 42.2, Kernel 4.4.76-1-default I have the following problem: When I attach my USB Storage Device during runtime it gets the device node name /dev/sdk assigned which is fine. If I ...
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2answers
6k views

How to create device files manually use mknod?

Linux 2.6.26.5 embedded. I need manually mount the root file system from busybox shell (initramfs). Because this Linux kernel not use devtmpfs, I have to create the basic device nodes manually, use ...
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2answers
104 views

How does 'eject' get processes to close file handles?

On my Mac, when I 'eject' a network-mounted share, my Mac presents me with the following message, and attempts to get processes to close open file handles and cleanly dismount the share. My question ...
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0answers
1k views

How to get the specific serial port on usb-serial hub in Linux

I have a Linux machine with a connected USB hub (5 ports), and I also have a serial hub (8 serial ports) connected to this USB hub. It looks as follows: Linux -> usb hub -> usb-serial hub -> serial ...
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2answers
303 views

Why does Fedora have two `ptmx` files?

I know that the file /dev/ptmx is used to generate a master file for a pseudo-terminal. But I have found out that Fedora has another ptmx file (/dev/pts/ptmx): What is the purpose of this second file?...
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2answers
173 views

Disconnected block device remains in /dev/, sync commands unkillable

I'm running Linux Mint 18/2 with 4.10.0-38-lowlatency kernel and KDE5 desktop. I'm testing lots of USB flash memory with a custom bash script and f3 and I had a strange situation today. One drive ...
3
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0answers
369 views

Loading a kernel module at run time using “compatible” property of device node in device-tree

If I know the "compatible" property string of a device(from the device tree), can I use it at runtime to load the corresponding kernel driver module? I do not have access to the driver source. I am ...
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0answers
717 views

/dev/random entropy on readonly file system

My hostapd works very well on my raspberry Pi3. But if I put root filesystem in readonly, it does not work. I have put some folders like /var/run and /tmp in a ramdisk filesystem. I have seen ...
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1answer
805 views

How to interpret SCSI device (sd) timeout logs

In /var/log/messages, I find the following log: Oct 23 21:48:53 localhost kernel: sd 3:0:0:0: timing out command, waited 180s Please explain the values that are separated by colons. Also where ...
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1answer
32 views

How can I setup a read/write device that spawns a program?

I don't know if this is possible but I had no idea how to research this concept. Is it possible and if how do I... create a device file (i.e. /dev/remoteclip) that will, when written to or read from, ...
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2answers
10k views

Manipulating /dev/video

I'd like to take the video stream from /dev/video0, apply some effects or changes and make the result available on /dev/video1. /dev/video0 ---> Apply Effects ---> /dev/video1 For example, mplayer ...
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0answers
147 views

Identify device by its handler

I'm looking for a robust method for identifying a device's type (mouse, keyboard, joystick) by its input event handler. There are parameters which cannot be trusted, such as device name/vendor-id etc....
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1answer
611 views

Device Node not created

I am trying to connect a new device (Keysight U2722A) and it does not appear in /dev. I have tried this in Ubuntu, Fedora, and openSuse, all with the same results. Currently working in Fedora. When ...
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0answers
363 views

Remove extra non-working scanners

I tried to add a USB scanner to my system without any luck and now when I start XSane or Image Scan! for Linux I get a list of non-working scanners. How these can be removed? I've tried: # pacman -...
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1answer
2k views

How do you determine the capabilities of a WebCam?

I have a collection of WebCam's lying around. Some of them are new, some go back a decade -- have to love not having to "upgrade" devices in Linux! Somehow I've developed the impression that ...
4
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2answers
2k views

Debian USB automount

Got my USB flash automount broken after reboot. Using Debian 6, GNOME 2 My NTFS hard disk is still mounting correctly. When i connect my Android smartphone (with SD and local drive) my messages log ...
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1answer
148 views

fdisk with option '-l' - how does it get info about device?

I'm experimenting with a software defined device, trying to force it to work with block size = 512 bytes, but it looks like the Linux doesn't want that. I've forced the device to report minimal ...
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1answer
3k views

How to debug a driver failing to bind to a device on Linux?

I am trying to figure out why the following device is not setup to its driver on my Creator CI20. For reference I am using a Linux kernel v4.13.0 and doing the compilation locally: make ARCH=mips ...