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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3
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4answers
193 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 ...
2
votes
1answer
3k views

“PS/2 Generic Mouse” gets lost. How to reload without reboot?

I am running Ubuntu 12.04LTS on a ThinkPad E420s. My Trackpoint is recognized as "PS/2 Generic Mouse". My problem is that it doesn't load/disappears after booting or after suspension. I can't move ...
6
votes
1answer
866 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 ...
0
votes
0answers
16 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 ...
0
votes
2answers
18 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.
6
votes
2answers
4k views

Using bash's `/dev/udp`, how would I know if the port was open?

I do not have access to netcat or nmap so I'm trying to use bash and the /dev/udp/ special files to test ports. I could do something like: echo "" > /dev/udp/example.com/8000 But $? is always 0 ...
2
votes
1answer
111 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 ...
1
vote
0answers
105 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 ...
16
votes
1answer
7k views

Difference between /dev and /sys/class?

What is the difference between the device representation in /dev and the one in /sys/class? Is one preferred over the other? Is there something one offers and the other doesn't?
0
votes
0answers
85 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 ...
0
votes
0answers
16 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 ...
1
vote
1answer
33 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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0answers
60 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 ...
9
votes
2answers
15k views

How to Reset/Cycle Power to a PCIe Device?

I have a PCIe device that only works correctly when the computer is fully powered off then on again. Issuing a simple reboot or reboot -p command does not appear to cycle the power to the PCIe card, ...
2
votes
2answers
851 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 ...
2
votes
1answer
61 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 ...
1
vote
0answers
64 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: $ ...
84
votes
6answers
6k views

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 ...
0
votes
1answer
102 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. ...
1
vote
1answer
74 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 ...
1
vote
1answer
99 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 ...
3
votes
0answers
32 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 ...
0
votes
0answers
49 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 ...
4
votes
1answer
150 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 ...
10
votes
1answer
1k views

How do I let an SDL app (not running as root) use the console

I want to use an SDL-based program to display graphics on the console, without having to log on from the console, and without running the program as root. For example, I want to be able to run it via ...
0
votes
0answers
51 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 ...
1
vote
0answers
184 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 ...
0
votes
2answers
200 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: ...
4
votes
1answer
107 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 ...
1
vote
0answers
42 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 ...
2
votes
2answers
87 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 ...
4
votes
1answer
9k 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 ...
1
vote
2answers
138 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 ...
0
votes
1answer
163 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 ...
1
vote
0answers
135 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 ...
7
votes
1answer
525 views

Why does a device show up as hidraw instead of hiddev?

I read the kernel documentation for hidraw and hiddev, and I understand the differences, but I am wondering how the kernel decides whether or not a device should show up as /dev/hidraw* or ...
5
votes
2answers
1k views

Udev rule to match multiple node USB device

I have a 3G/GPS device that creates 5 tty nodes, although it's only one physical USB connection. Basically, a multi port usb-serial adapter. I'm trying to create some udev rules to make sure those ...
0
votes
1answer
322 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?
5
votes
2answers
1k 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 ...
0
votes
0answers
66 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. ...
2
votes
3answers
314 views

/dev/console points to tty0?

I've been trying to understand the /dev/console device, but there are a few things I'm not clear on: What is the purpose of this device? From what I can gather it's just a place for the kernel to ...
1
vote
0answers
73 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 ...
3
votes
2answers
92 views

How to temporarily disable mouse device?

I have wireless USB keyboard and mouse combo. I need a way to disable mouse while leaving keyboard function working and a way to enable it again after some time. I don't use X and I can't make it in ...
0
votes
0answers
137 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 ...
0
votes
1answer
117 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?
2
votes
1answer
62 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. > ...
0
votes
1answer
181 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 ...
3
votes
1answer
62 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?
1
vote
0answers
67 views

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 ...
22
votes
3answers
13k views

Understanding /dev and its subdirs and files

$ ls -l /dev/stdin /dev/fd/0 lrwx------ 1 tim tim 64 2011-08-07 09:53 /dev/fd/0 -> /dev/pts/2 lrwxrwxrwx 1 root root 15 2011-08-06 08:14 /dev/stdin -> /proc/self/fd/0 $ ls -l /dev/pts/2 ...