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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iostat ( column svctm is not trusted any more ) what to use instead?

I'm running a Linux Server with "Oracle Linux Server release 6.5" which is pretty much the same as RedHat Version. I need to determine the latency on my disk devices. The man page of the iostat ...
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Writing serial data to /dev/dsp [migrated]

I am trying to write a c++ program to read serial data from an arduino micro controller and play it through my speaker. int main() { int ser_val; ifstream ...
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1answer
23 views

uuid, device number, and device file for a device

In Linux, I would like to know about the differences in purposes and usages of uuid, device (major and minor) number, and device file for a device. They all seem to me to identify a device (and may ...
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1answer
23 views

Major and minor numbers of a partition

$ stat new File: ‘new’ Size: 928 Blocks: 8 IO Block: 4096 regular file Device: 804h/2052d Inode: 28188755 Links: 1 Access: (0622/-rw--w--w-) Uid: ( 1000/ t) Gid: ( ...
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1answer
7 views

Is it possible read every serial device's data?

Reading serial data is something ordinary when comes from devices connected by direct serial 9-pin cables. But happens with usb devices ? Considering that actually USB is a Universal Serial Bus, is it ...
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2answers
31 views

How does bash print to the screen if not with a framebuffer? [duplicate]

I noticed that a framebuffer doesn't always exist on some systems. In these cases, how does bash print to the screen (assuming it ever uses fb devices at all)? Since there's no framebuffer device, ...
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2answers
22 views

Send a message to a “screen” to be received by a device on /dev

My question may looks trivial... But it's because despite of my long experience of linux/unix/osx systems, I found myself lacking some basic notions. I created a little bluetooth/arduino switch to ...
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4answers
108 views

Why does mknod require root privileges?

I noticed that the mknod command required root privileges when a creating a node other than a regular file, FIFO or a Unix socket. Why is that? How can a regular user harm a system or compromise ...
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1answer
709 views

Difference between /dev/null and /dev/zero

When trying to redirect to /dev/null and /dev/zero, the output it is discarded. It seems both /dev/null and /dev/zero accept and discard all input. So, what is the difference between /dev/null and ...
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14 views

How is Xserver able to tell which device is a mouse or a keyboard?

In these days we don't have to create a custom configuration that sets our devices up, at least when it comes to Xserver. But sometimes you want to change some default parameters. When you do it, you ...
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2answers
17 views

How can I see the dismounted devices

How can I see if the usb device has been dismounted? Because when I did fdisk -l the information is the same, before and after the ran command umount /dev/usb.
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42 views

when running `udevadm test`: `no db file to read /run/udev/data/+gpio_sw:PA7: No such file or directory`

I am trying to write an udev rule that matches a GPIO Pin of my Orange Pi (the GPIOs use the gpio-sunxi kernel module). My ultimate goal is to let users who are member of a particular group access ...
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1answer
46 views

Access iphone storage as device/partition

I am working on a project, in which the ultimate goal is to successfully wipe iOS from an iPhone and install TinyCore Linux in it's place. I expected the iPhone to function like an external drive when ...
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46 views

Linux doesn't recognize the SSD it's booting from!

I've extended a computer by a SSD and the BIOS recognizes it (and shows its name), but neither Ubuntu 14.4 nor Knoppix 7.6 show it in fdisk's output. Then I copied Fedora 23 WS Live to that SSD (on ...
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9 views

Devices for Analog I/O gone from /dev after reboot

I have a system using Centos 6.6 and another system using RHEL 6.6 on the same architecture that both need analog I/O drivers to communicate with sensors that will be attached to the device. Thus, I ...
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1answer
28 views

Are device files implemented by device drivers or OS kernels?

Device files are interfaces of device drivers to user programs. In Linux, is a device file implemented directly by its corresponding device driver, or by the OS kernel (excluding the device driver)?
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42 views

Write my own sound card driver [closed]

I would like to write my own sound card driver, in order to use my output jack as a PWM (to control a motor). When I run "lspci", the sound card is : Audio device: Intel Corporation 5 Series/3400 ...
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24 views

There is no /proc/bus/usb directory

I'm running a centos VM on ESXi. Does the /proc/bus/usb directory not show up until a USB device is connected? I just added a USB controller to the VM (it previously had non) and ran lsusb: $ ...
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100 views

how to get bus id of an usb device

I would like to bind/unbind my usb device - a wireless adapter. echo -n "1-1:1.0" > /sys/bus/usb/drivers/ub/unbind So to able to do that, I need the bus ID. lsusb prints out the following: Bus ...
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1answer
35 views

How to swap out the driver of a network device on a running Debian Linux box?

I've got an embedded/headless Debian Linux box which boots from a read-only filesystem image. The configuration is set up so that I can (seemingly) write to the filesystem, but any changes to the ...
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1answer
30 views

What is /proc/dma? Is it just for legacy support?

I reading a Linux book that told me I can check the dma channels by reading /proc/dma. This is what I see when I run cat /proc/dma: 2: floppy 4: cascade I'm confused because that looks like old ...
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1answer
41 views

Unable to connect to USB CDC device

I have an 8 channel USB Relay board which I have connected via USB. The manual for the board states that: To use this product with Linux, USB CDC driver needs to be compiled in with the kernel. ...
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6answers
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How are “/dev” Linux files created?

There are special files in Linux that are not really files... The most notable and clear examples of these are in the dev folder, "files" like: /dev/null - Ignores anything you write to the file ...
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1answer
50 views

In udev, what kind of device events match ACTION==“change”?

The udev rules I've created so far only deal with devices being added or removed, i.e.: ACTION=="add"... or ACTION=="remove"... I've come across an example of a rule that seems to deal with device ...
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0answers
26 views

Enumerate valid values for mknod

I have access to an embedded device which has a bunch of block/char files under /dev. However, this is not a satisfying description of the hardware, because since the firmware is shared with small ...
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29 views

Tweaking the tripwire policy to stop checking for /dev/pts/x

Trying to streamline my Tripwire policy file, I see that I get a lot of chatter in every daily check report about ------------------------------------------------------------------------------ Rule ...
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1answer
144 views

What happened to /dev/raw/?

I am reading an article on LWN and it has an important statement: Raw devices (/dev/raw/rawN) are a special case of O_DIRECT I/O. These devices can be opened without specifying O_DIRECT, but ...
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33 views

How to switch Huawei CDMA 2252+ to usb from cd-rom?

I have Huawei CDMA 2252+ phone and i want to connect it to linux to send sms. In Fedora 15 (64bit) it is taken as cdrom. This is the output of dmesg after the phone plug in. [10887.524339] USB Mass ...
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2answers
123 views

sysfs and devtmpfs

Ok, Ulrich Dangel explains very well the difference between devtmpfs and udev but what happen with sysfs I understand that the kernel use sysfs to export device nodes to user space to be used by udev, ...
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2answers
103 views

Where do the logs directed to /dev/console go?

I'm studying RHEL 7. If I add this line to rsyslog.conf: kern.notice /dev/console Where will the messages with facility "kernel" and priority "notice" be logged? If I run this command: ...
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35 views

Can you create a read only encrypted partition that root cannot write to (or remount)?

I have an encrypted partition that I would like to be mounted as read only. The catch is that I do not want a root user to be able to remount the partition as read-write unless they have the ...
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2answers
60 views

Changing ownership on /dev/fuse - security issues?

In some distributions /dev/fuse is owned by root:fuse while in other distributions /dev/fuse is owned by root:root. I'm using CentOS which belongs to the former set of distributions. And I'm wondering ...
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1answer
90 views

Where is the default device name (e.g. /dev/ttyUSBx) specified?

I'm investigating dynamic device name mapping via udev. The goal: On a multi user system, each user can allocate and free devices like usb-serial converters or PCIe cards (FPGAs). If an user ...
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1answer
102 views

No /dev/ttyusb* in Linux

I want to do some serial programming using Python Serial, and all examples I've seen online for USB set the port parameter to "/dev/ttyUSB*" . But on my system, there is no "/dev/ttyUSB*" inspite of ...
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2answers
103 views

Is UUID really unique? why can we assign multiple UUIDs to single slice of disk

All the web content and its acronym explains it as Uniquely identifier. But when i try to create another device, lets say swap in my case and assign the UUID, i am able to assign many UUIDs to single ...
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77 views

udev: Passing parameters via $attr{key} does not work. How to solve it?

I want to enumerate my USB-UART bridges with my own script. The script shall be called with some attributes and return a new devfs node name. I tested the script on console: ./rc3e.py -d ...
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1answer
170 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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2answers
564 views

Arch linux can't login

My problem is that I can't login. If I try to loggin with correct username and password it doesn't do anything. I have error message on boot failed to create static device Nodes in /dev . This ...
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3answers
257 views

Creating a character device file

How to create the character device files? I have tried cat > xxx^c But I can't create a character device file
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40 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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2answers
639 views

How Linux uses /dev/tty and /dev/tty0

I can see the difference between /dev/tty and /dev/tty0 by testing the provided method from this question. But I really wonder about the practical usage of those devices (like situations they will be ...
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44 views

Disable embedded keyboard when in a tty

I've been lately working on a netbook. I like to connected an external keyboard and mouse to it whenever I can, and I put the keyboard over the embedded keyboard. When on X, I used xinput to disable ...
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68 views

(Linux) unable to mount from initramfs

I am trying to install Linux (Debian) on a new laptop. This requires special care because the laptop keyboard needs a kernel patch (and I have not compiled a kernel for about 10 years). Also, because ...
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1answer
83 views

Linux UART IO File

How bytes received on UART device are stored in some serial Linux devices /dev/ttyS? How to read them? What is the procedure? Should that device file be closed, when new data is arriving?
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1answer
50 views

How many distinct video cards do I have?

I'm logged on to a remote machine and I'm trying to determine how many video cards are installed. The machine was built for CUDA operations so it's likely to have more than one NVIDIA card. > ...
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1answer
106 views

how to set i2c bus to soc audio codec

I'm working on an audio codec driver for cs4245 device. It's controlled by i2c. I have 2 hardwares (devel-board), one of the them has the codec attached to i2c-1 and another to i2c-2. The first one is ...
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1answer
57 views

Which device is working

I have one dvb-t and one dvb-s card in my system which are in /dev/dvb/adapter0 and /dev/dvb/adapter1 Is there a way to find out which card is currently working? and which one isn't?
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Write shrunken .img file to device file

I have a backup image of a device file /dev/sda3 that I created using: dd if=/dev/sda3 of=~/sda3.img. The image is very large, so I have re-sized it to remove empty space. My question is can I ...
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149 views

Unable to find Documents on iPad device when mounted

It seems that this is a common problem, but there haven't been any satisfactory solutions posted yet, despite existing for years. Briefly, the problem is that when I mount my iPad in Linux Mint, I ...
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58 views

Help me to find my speakers and headphone paths (name of PCM device)

I am really confused trying to get my speakers and headphone device PCM names like a "hw:x,x" or something like that; cat /proc/asound/devices 2: [ 0] : control 3: [ 0- 0]: digital audio ...