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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279 views

How create a second midi device?

I need create two or more MIDI devices. Using the command "modprobe snd-virmidi", I create one midi device: "/dev/midi1". This device is connect in port 20. I can see in "aconnect -l" and put with ...
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1answer
811 views

How can I make a device driver communicate with hardware?

I have got user-space app ready, device file mknoded, device driver insmoded into kernel, and there is the device with UART protocol. I am trying to find out what happens between Device Driver (it has ...
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2answers
216 views

cloning a linux image using dd

If I wish to clone my Linux image using the dd utility, I can do for example dd if=/dev/SDX of=/dev/SDY, where SDX is the internal memory device where the Linux image is stored, and SDY is the ...
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0answers
176 views

How exactly do the Linux display device files work? [closed]

I don't really understand how the Linux display device files work and interact together. What files in the /dev tree need to go where and where do they need to connect/point to, in order to show a ...
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1answer
430 views

Which Unix-like system really provides the /dev/tcp special file?

I know /dev/tcp/<host>/<port> is a magic path handled specifically by some shells in redirections. But according to man bash: If the operating system on which bash is running provides ...
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34 views

How about the work mechanism of kudzu in older RHEL version while the system is running ?

It seems that the kudzu can only take effect for new devices while the system starts up ! For example, although we can run the kudzu to find the new devices online, such as disks, but in fact no any ...
2
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1answer
400 views

Access grab state of evdev device

I need to retrieved the grab state of an evdev device in a program. More specifically, I need to retrieve the state of the grab pointer in the evdev struct seen here: https://elixir.bootlin.com/linux/...
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0answers
929 views

systemd-nspawn: how to allow access to all devices?

I'm trying to create a rough equivalent of Docker's --privileged in a systemd container, but I've got no idea how to allow the container to access all of the devices available on the host (without ...
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0answers
412 views

How to script AT command to modem?

Every time my USB modem (/dev/dlinkModem) gets unplugged it defaults to "radio disabled mode" (AT+CFUN:4). I can easily enough call AT+CFUN:1 through the minicom application console to enable radio ...
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1answer
783 views

Creating Persistant Symbolic Link -Linux

I have a cloud server, where a block device (/dev/xvdb1 with filesystem ext3) is attached . I want to create a persistent symlink (/dev/test_link) which should always target to (/dev/xvdb1) using ...
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0answers
2k views

When i plug in usb camera i get 2 devices

When I plug in the camera to Linux then I get 2 devices /dev/video0 and /dev/video1 Why is that happens and is that normal? Odd numbered devices do not work. /dev/v4l/by-path looks like that: ...
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462 views

how to fix the devices name ordering in guest vm (devices name ordering changed after reboot vm by virsh)

my devices xml define: first vm only has a root volume, <disk type='file' device='disk' snapshot='external'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/dev/...
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1answer
35 views

Can I refer to current clipboard content as a file?

I'd like to select-and-copy some text to clipboard and then to send it via Bluetooth to my phone. But this requires to open a file to send. Well, I know about programs like xsel or xclip, but here it ...
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0answers
75 views

How to enable all users to access arduino card?

I am trying to set up Linux (Debian 9) machines in a computer lab to let users plug in their arduino interface and flash their device with their code. I do not really know about arduino and so on, ...
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0answers
2k views

Ubuntu boot fails on Lenovo P52 Thinkpad when hybrid display is set in BIOS [closed]

Booting to Ubuntu 12.04.5 LTS fails when the display is set to 'hybrid' in the BIOS (using Nvidia driver 415) When I switch to 'discrete', then it boots to Ubuntu OK. Because I am dual booting with ...
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3answers
3k views

How to check if stdin is /dev/null from the shell?

On Linux, is there a way for a shell script to check if its standard input is redirected from the null device (1, 3) *, ideally without reading anything? The expected behavior would be: ./...
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1answer
1k views

UIO device files /dev/uioX are not created on Linux Debian

I'm having a problem on Linux Debian 9.6. Although I have UIO support compiled into the kernel, the /dev/uioX device files are not beeing created. root@machine:~# zcat /proc/config.gz | grep UIO ...
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0answers
70 views

Webcam and Desktop composite with v4l2loopback?

Is there anyway to do a composite video setup where the webcam is overlain onto the desktop and output as a video device (simulated webcam)?
2
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0answers
217 views

Is there any standard for naming RS-485 tty devices/device aliases in Linux?

I know, that there are some standards in tty naming. There is ttyUSBx for USB to serial converters, ttySx for RS-232, ttyAMAx on ARM devices, but I can't find anything about conventions in RS-485 ...
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1answer
2k views

Correct way to fix missing device file in /dev?

I am using a proprietary PCI card from Sensoray in my Ubunut 14.04 machine (I intend to upgrade to 18.04 soon). The card comes with the source code for the driver and a Makefile to build and install ...
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1answer
2k views

Emulating a character device from userspace

We are currently working on building a system for data visualisation for different sensors. To make development of the Linux application possible we would need to emulate the behaviour of the ...
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1answer
139 views

Rip-off (an ncurses term) single bottom line out of /dev/tty terminal, is it possible?

Ncurses allows to separate a single line from screen, at level of physical screen (curscr), to devote it to e.g. a title bar, thus also creating a logical screen (stdscr), devoted to application's ...
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1answer
4k views

USB device (keyboard or mouse) shows in `lsusb` but does not work if it is the second USB device to be plugged in

I've been having a strange issue the past couple of months where the second USB device to be plugged into my laptop is unresponsive, despite showing up in lsusb and dmesg seemingly without issue. ...
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4answers
1k views

How to find the Absolute device name

I had a homework question which I answered correctly: Use lvdisplay to discover information about the VG Name found in the previous question. What is the first LV Path which is using the volume ...
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1answer
85 views

What is the relation between a line in cpu cache and a page in main memory (and block in disk)?

Computer Systems: A Programmer's Perspective (2nd Edition) [Randal E. Bryant, David R. O'Hallaron] says A block is a fixed-sized packet of information that moves back and forth between a cache and ...
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1answer
64 views

How is a sequentially accessible device made randomly accessible?

If a device offers only sequential access not random access, can a device driver or a file system make the device look like randomly accessible to users? If yes, is this done by providing buffer/...
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1answer
1k views

Can filesystems be created only on block devices, but not on character devices?

Can filesystems be created only on block devices, but not on character devices? Can a filesystem be viewed as a block device itself (for example, when programming to use a file system)? My guess is ...
2
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1answer
267 views

Is devtmpfs special with respect to namespaces? a permissions problem

I'm wondering if devtmpfs is special with respect to namespaces. Here's my system info (using Vagrant for testing) vagrant@ubuntu-xenial:~/test$ uname -a Linux ubuntu-xenial 4.4.0-135-generic #161-...
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1answer
185 views

udev ACTION add isn't working

I'm trying to use udev for some basic actions, in this case the idea is to launch a simple script. The problem is that when I use this rule: ACTION=="remove", ENV{ID_FS_LABEL}=="NAMEHERE", KERNEL=="...
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2answers
1k views

Why can I (or cannot) mount a mounted device again? What is happening?

Why can I (or cannot) mount a mounted device again? What is happening? For example: /tmp/test$ sudo mount /dev/sda5 ./1;echo ${?} 0 /tmp/test$ sudo mount /dev/sda5 ./2;echo ${?} 0 /tmp/test$ sudo ...
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0answers
27 views

Scenario to use the sg driver

Is there any device commonly controlled by SCSI generic driver (sg) in Linux today? I am curious about that. Currently I just know the mtx tool which controls robots in tape libraries via sg driver.
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2answers
8k views

How to use dd if=/dev/mem in place of devmem ?

It seems like root@testbox:~# dd if=/dev/mem bs=1 count=4 skip=2149646336 | hd should be nearly equivalent to root@testbox:~# devmem 2149646336 32 But, while devmem works great, that dd invocation ...
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2answers
60 views

How to determine if an unmounted CD/DVD is in the drive?

Under Linux, is there any way to get a yes/no answer to whether or a CD/DVD drive contains a disc which isn't mounted but which can be mounted or written to?
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0answers
124 views

How can I xor two block devices together?

I'm looking for a way to create a virtual block device that when accessed returns the XOR of two block devices. I feel like dmsetup would be used here somewhere but I can't find anything related to ...
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1answer
3k views

Udev Rules Not Running

I'm playing with Udev Rules on OpenSuse Leap, and I'm trying to run a simple and small script once a USB device is plugged into my system. However, my script which I added in my keyword "RUN+=" does ...
2
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1answer
90 views

How to link a tunX interface to a specific OpenVPN instance?

I known that I can give a specific name to the TUN interface using --dev option, but I didn't and I have now on a router machine something like a hundred client configs. with less clients I was able ...
0
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1answer
322 views

Given a block device file, how can I list all relevant partions?

Given a device file (ex: /dev/sda) how can I get a list of all relevant partitions? Expected input: /dev/sda Expected output: /dev/sda1 /dev/sda2 /dev/sda3 ... I know there are many ways to get ...
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2answers
68 views

Skipping the middle mapping with cryptsetup luksOpen

I'm mounting a bunch of encrypted disks like so cryptsetup luksOpen some_source some_mapping && mount /dev/mapper/some_mapping /some_mountpoint How can I abstract away the middle mapping? I ...
2
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1answer
534 views

SPI driver for Debian

This is the Linux: PRETTY_NAME="Debian GNU/Linux 8 (jessie)" NAME="Debian GNU/Linux" VERSION_ID="8" VERSION="8 (jessie)" ID=debian The Kernel version is: 4.1....
5
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3answers
3k views

Make tar from /dev/stdin file

What I'm looking for is a way to pass in arbitrary data through STDIN, and have it get tar'd up as if its a normal file. I tried this $ echo test | tar -cf test.tar /dev/stdin and that gives me a ...
5
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2answers
3k views

How to completely inhibit lid switch events?

Context: Due to missing drivers for my 2-in-1 convertible, folding the screen back only triggers a lid switch event. This causes the laptop to suspend or, when "Suspend when laptop lid is closed" is ...
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1answer
1k views

How to create multiple devices in a /dev/ subdirectory (kernel driver)

I'm writing a kernel module. I can easily create a character device in /dev/ but I want to have 3 devices available to my user and it would be nice to put them all under a /dev/ subdirectory. ...
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1answer
68 views

Why raspbian lite powers off when doing `sudo cat /dev/char/10:130`?

I did on a terminal sudo cat /dev/char/10:130, which in the uevent has name of watchdog, and it outputs a message from the kernel saying that watchdog did not stop !, and after a couple of second it ...
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0answers
989 views

What is the difference between `/dev/input/event*` and `/dev/input/mouse*` according to mouses?

Suppose my mouse is associated to /dev/.../event1 and /dev/.../mouse1. I was reading the byte streams of those files, and I noticed that event1 gives much more information than mouse1, which ...
19
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4answers
78k views

PKCS#7 signature not signed with a trusted key

Installed Ubuntu with SIP disabled on MacBook 2017 - 0 issues, booted in seconds. I have been building it out and created a problem while trying to make the WiFi work. At some point (it was very late)...
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1answer
272 views

How to deny all access to /dev/sda? [closed]

I would like even applications not to be able to access /dev/sda . If possible, I would even like to disallow root applications from accessing it, but that is not as important.
1
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1answer
847 views

what is DEVLINKS in the output of udevadm info --query=property --name=/dev/mmcblk0

I was looking at the udev information but couldn't find out anywhere. What does DEVLINKS signify also what are these values dev/disk/by-id/mmc-008G30_0xf281d20d & /dev/disk/by-path/platform-...
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0answers
32 views

Ethernet malfunction when booting with extra device on /dev

I have a customized Linux distro (created via buildroot) running on an embedded platform. The system consists in a processing module (Based on Samsung Exynos 4412 microprocessor) with a base board for ...
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0answers
40 views

Drive emulation at driver level

I would like to emulate a virtual SED at driver level. The goal is to develop/simulate the "firmware" of a drive, and map driver interface commands to an app which would handle interface specific ...
1
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1answer
427 views

How do you use SSHFS to work on drives in /dev/

My laptop for some reason will not power an external 2.5" HDD, so I am using a Raspberry PI to connect to the drive. The problem is, I am struggling to perform tasks such as formatting disks and ...

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