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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).

2
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2answers
29 views

lsblk column “RAND” aka “adds randomness” - what does it mean?

Running lsblk (an excellent command for getting info about the disk configuration from within scripts and OS-agnostic high-level languages) on Fedora 29 like so: $ lsblk --output NAME,FSTYPE,ROTA,...
0
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0answers
21 views

Who is causing extremely high CPU usage when writing to SSD?

When writing to SSD (regardless if over file system or directly into /dev/sda) I observe extremely high CPU usage, with top showing CPU: 0% usr 53% sys 0% nic 9% idle 27% io 0% irq 9% ...
0
votes
0answers
22 views

Multiple /dev/video for one physical device

First some specs: my computer is an HP EliteBook 8460p. It comes with an integrated Chicony HP HD webcam. My issue is that a lot of applications (well, at least Skype and guvcview) are displaying ...
1
vote
2answers
60 views

The concept of “Airplane Mode” in Linux

When installing a Ubuntu, Manjaro or other Graphical Linux distro on laptop, when press the airplane mode button on laptop, Airplane mode can be enabled. How the concept of airplane mode works in ...
0
votes
2answers
113 views

Linux block devices naming

I am a bit confused with how linux hard drive/ storage device, block files are named. My questions are: How are IDE devices and partitions named? How are EIDE devices and partitions named? How are ...
0
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0answers
16 views

How to configure multiple SPI devices on Linux

I have an embedded Linux system (F&S PicoComA5) that has shipped with a pre-configured Linux Kernel + buildroot system. By default, only one SPI device is pre-configured, appearing in the system ...
0
votes
1answer
17 views

How to choose between sound outputs without unplugging hardware?

I am currently running the following: 4.15.0-46-generic GNU/Linux Distributor ID: LinuxMint Release: 19.1 Codename: tessa I have my headphones plugged into their dedicated port, however, I ...
-1
votes
1answer
70 views

Why every device in Linux is a file or folder ? what are the advantages? [closed]

Why every device in Linux is a file or folder ? what are the advantages ? and what is the necessity of /dev/sda1 , /dev/sda2 or /dev/sda3 file ? it's size is 0 bytes .and after mounting the hard disk ...
0
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0answers
19 views

1 NFC Device found but won't list it

I am running a VM of Kali Linux. I have an ACR122U NFC Card Reader. One problem I have been having is that when I attach the NFC reader to my PC and run nfc-scan-device -v, it returns "1 NFC device ...
0
votes
1answer
80 views

DRBD comes up after reboot with Connected Diskless/Diskless

After an unattented power loss, facing a major issue, every reboot the DBRB comes up with Connected Diskless/Diskless status. main problems: dump-md response: Found meta data is "unclean" ...
2
votes
2answers
142 views

A start job is running for eth0

I am using a new installation of Arch Linux and whenever I boot my system I have to wait for 90 seconds as there is a start job running for my network interfaces. I installed Arch yesterday and ...
0
votes
0answers
8 views

Disconnected onewire devices still exist after echo 1 > w1_master_search

I'm working on embedded device where user connects and disconnects onewire sensors sometimes. Sensors are connected to DS2482 device, which is I2C to 1Wire converter. DS2482 is supported by Linux ...
0
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0answers
28 views

Device Major number changed in /proc/devices after restart

I installed my device driver using mknod and operating system assigned a major number for it. (Saw 236 in /proc/devices) But when i restart the machine and check the /proc/devices again i saw that ...
0
votes
1answer
31 views

What is a meta device?

man pvcreate says pvcreate initializes a PV so that it is recognized as belonging to LVM, and allows the PV to be used in a VG. A PV can be a disk partition, whole disk,meta device, or loopback ...
0
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0answers
93 views

flush tty device buffer from terminal

I have a serial device on /dev/ttyAMA0. I have program written in C that communicates with this device. But apart from the C program I sometimes need to input some configuration data from terminal, ...
2
votes
1answer
31 views

Why can't I open these device nodes?

[root@archlinux xtricman]# ls -l /dev/pts total 0 crw--w---- 1 xtricman tty 136, 0 Feb 24 19:24 0 c--------- 1 root root 5, 2 Feb 24 19:10 ptmx [root@archlinux xtricman]# ls -l /mnt total 12 ...
2
votes
1answer
105 views

Get video device on embedded Linux SoC

I'm trying to find the camera module device of an IP camera (running Linux), without much success. My main objective is to find the camera stream, so I can attach an RTSP server. Update 26/02/2019 ...
0
votes
1answer
78 views

Possible to force udev to create specific device event number, or change device event numbers

I have a kernel module that reads usb keyboard input specifically from /dev/input/event2 and /dev/input/event3. On some devices the keyboard doesn't get assigned event2 and event3, it gets assigned /...
0
votes
2answers
47 views

What is the default behaviour when we mount filesystem with `nodev` option?

I read this in "RH413 Red Hat Server Hardening" course that we mount the filesystems with nodev which then does not allow the special files/devices to be mounted from it. However, it did not show an ...
2
votes
1answer
64 views

Why does terminal takes input line by line?

If I use: strace echo 'a b c' > file The bottom lines are: write(1, "a\nb\nc\nd\n", 8) = 8 but in strace echo 'a b c d' > /dev/pts/0 These lines are: write(1, "a\n", 2) ...
23
votes
1answer
3k views

Why don't reads from /dev/zero count as IO_RBYTES?

I am emptying out a hard drive on some Linux 4.x OS using this command: sudo sh -c 'pv -pterb /dev/zero > /dev/sda' And I opened another tty and started sudo htop and noticed this: PID USER ...
0
votes
0answers
18 views

What is the difference between a Device File and a Device Node?

I was reading an article that mentioned device nodes, and didn't define what they were. Wikipedia also mentioned device node in the device file article but didn't specify what the difference is. Are ...
0
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0answers
41 views

How does linux uses device files stored in /dev? [duplicate]

I really got confused how kernel/device drivers use device files? What does happen when we read some file from a device using cat file1.txt? Do device driver copy the content to these files? If yes ...
2
votes
2answers
96 views

What do device type numbers mean?

file /dev/* prints the description of a bunch of files as "block special (M/N)" and "character special (M/N)", where M and N are numbers. For example: $ file /dev/null /dev/null: character special (1/...
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0answers
65 views

Flash drive detected by lsusb but not by fdisk

I try to format SanDisk Ultra microSDHC UHS-I Card with adapter but it does not appear on fdisk -l. However, it does appear on lsusb as Bus 001 Device 006: ID 1908:0222 GEMBIRD
1
vote
1answer
25 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 ...
0
votes
1answer
91 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 ...
0
votes
2answers
91 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 ...
2
votes
0answers
107 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 ...
9
votes
1answer
353 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 ...
0
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0answers
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
votes
1answer
62 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/...
2
votes
0answers
109 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 ...
1
vote
0answers
130 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 ...
0
votes
1answer
74 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 ...
1
vote
0answers
118 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: ...
2
votes
0answers
31 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/...
1
vote
0answers
25 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 ...
0
votes
0answers
38 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, ...
3
votes
1answer
1k views

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

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 ...
8
votes
3answers
2k 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: ./...
0
votes
1answer
135 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 ...
2
votes
0answers
36 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)?
1
vote
0answers
73 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 ...
0
votes
1answer
170 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 ...
1
vote
0answers
326 views

Disk device paths Changes from xvd to sda, how do I change to xvd?, [closed]

OS Ubuntu '16.04.5 LTS' Hypervisor Xen This output is when sda df -h Filesystem Size Used Avail Use% Mounted on udev 16G 4.0K 16G 1% /dev tmpfs 3.2G 1.3M 3.2G ...
0
votes
1answer
276 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 ...
0
votes
1answer
40 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 ...
2
votes
1answer
926 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. ...
-1
votes
2answers
165 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 ...