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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2answers
381 views

Why doesn't `head -c 2 /dev/hwrng` work?

I have an Atmel 97SC3201 in my computer and set the following in the kernel: CONFIG_HW_RANDOM_TPM CONFIG_TCG_TPM CONFIG_TCG_ATMEL /dev has tpm0 and hwrng, but running this command returns the ...
5
votes
3answers
7k views

RHEL: Creating stable names for network interfaces

We have a RHEL 5.5 box with 8 interfaces. And the eth interface naming is flip flopping. Sometimes eth0 comes up on physical port 7th, and sometimes on another physical port. We want the naming to ...
3
votes
2answers
324 views

Automated partition selection in bash script

I'm trying to write a bash script to run from Linux on a CD or flashdrive that can mount Windows and change stuff, but I don't know how to go about detecting which partition/drive is Windows. My best ...
5
votes
2answers
3k views

Linux : Major and Minor device numbers

What types of devices fall under the major device number category and what types of devices fall under the minor device number category. What is the real difference between the two categories?
6
votes
1answer
7k 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, ...
7
votes
2answers
4k views

wlan number assignment

How or where does Linux determine the assignment of a network device? Specifically, wlan0 or wlan1 for wireless USB devices. I plugged in a TP USB wireless a while ago, and it was assigned wlan0. I ...
5
votes
1answer
3k views

Why do my SATA devices show up under /proc/scsi/scsi?

I have 3 SATA devices on my system. They show up under /proc/scsi/scsi, although these are not SCSI devices. Why do my SATA devices show up under the SCSI directory? $ cat /proc/scsi/scsi Attached ...
10
votes
2answers
7k views

set baud speed for tty

How do I set the baud speed for a specific tty (in this case a serial port)? I tried using stty -F /dev/tty.iap ispeed 19200 But get the error Invalid argument for every speed I try (2400, 4800, ...
2
votes
0answers
157 views

Block Devices & Partitions

I partitioned a microSD card (mmcblk1) into two partitions mmcblk1p1 and mmcblk1p2. If use a dedicated card reader I am able to see the entire SD card and its partitions using various disk management ...
0
votes
0answers
21 views

How to associate device to sata port disk [duplicate]

I have 2 hard disks connected to 2 sata ports. The disks are associated to /dev/sda and /dev/sdb. These hard disks are in software raid so it happens that the system can go for some time with only ...
1
vote
4answers
6k views

Updated Fedora 18 - no sound devices, just dummy output

So, yesterday I updated the recently released Fedora 18, this has been done: Packages Altered: Updated grubby-8.20-1.fc18.x86_64 @?fedora Update 8.22-1.fc18.x86_64 ...
2
votes
0answers
222 views

Webcam Device Driver to support H.264

I have a Creative Live Cam Connect HD (id: 041e:4093) and this webcam has an on-board H.264 encoder. Unfortunately v4l2 only inputs the feed as MJPG. $ v4l2-ctl --list-formats ioctl: VIDIOC_ENUM_FMT ...
0
votes
2answers
82 views

Changes to files don't show up until the partition is unmounted

I have a FAT32 filesystem mounted. After changing a file on it, I can read the file back and still see the old version. My changes don't actually persist until I unmount and remount the partition. Is ...
2
votes
1answer
137 views

What is the source of truth for currently active tty/pts connections?

I'm looking for a simple way to determine the number of currently logged in users, using only the filesystem and basic bash functions (instead of using binaries). The uptime binary appears to be ...
0
votes
1answer
702 views

remove /dev/mapper/fedora-root and /dev/mapper/fedora-swap

I want to replace Fedora 18 with Ubuntu but I have these devices listed when partitioning. I only have a hard disk labelled sda, where does these virtual device come from? How I do remove them?
28
votes
4answers
22k views

What is the mknod command used for?

I just started using Ubuntu as my main OS and I wanted to learn about things I should not do, and learn by the bad things people have done in the past. I came across these email about horror stories ...
5
votes
1answer
2k views

Query USB current

How can I obtain information about the amount of current negotiated by a device attached to a USB port? I am looking for information similar to this presented by OS X in terms of current available ...
0
votes
2answers
402 views

Problem mounting my iRiver story HD on Ubuntu

I would like to connect my iRiver Story HD to my ubuntu 12.04 machine but as I connect it I get this error: Unable to mount Story HD Error mounting: mount: wrong fs type, bad option, bad ...
15
votes
2answers
3k views

bash script to detect and record mouse movements?

I need to be able to record the mouse movements every so often (every .2 of a second for example) and have them in a coordinate representation instead of a diff. I found the following script: ...
3
votes
0answers
205 views

How to route one video device to multiple programs

I'd like to direct the output of a single capture card (Hauppauge PVR-150) to two programs: VLC (for streaming on LAN) and MythTV for scheduled recording. I think it's possible to do this with the ...
2
votes
1answer
96 views

Standard way to expose device file to userland applications running on an unprivileged user account?

I just finished the first version of a Linux kernel module I've written in C. The module creates a device file (/dev/wn0) that controls a USB device with three LED lights. For example, running as ...
5
votes
4answers
811 views

Testing, from a script, if audio devices are in silent?

Is there a default program where I can check if my audio devices are in silent? Edit: By silence, I mean that if there is something playing on that (not just activated or opened) Something like ...
0
votes
2answers
158 views

What files are being updated or written in /dev/sda?

root@host [/etc]# iostat -xk Linux 2.6.32-279.19.1.el6.x86_64 (host.superhostsite.com) 01/13/2013 _x86_64_ (24 CPU) avg-cpu: %user %nice %system %iowait %steal %idle ...
2
votes
0answers
197 views

Connected Android device - brings the network down?

I have dealt with sensitive development under Android, and have recently decided to switch to Linux now sit under (Mint 13 - KDE). But strangely, when the Android device is connected, my network goes ...
4
votes
2answers
9k 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 ...
11
votes
2answers
15k views

What are character special and block special files in a unix system?

How are character special files and block special files different from regular files in a Inix-like system? Why are they called “character special” and “block special” respectively?
15
votes
3answers
3k views

Monitor what is being sent to /dev/null?

Just for fun: Is there a way to monitor/capture/dump whatever is being written to /dev/null? On Debian, or FreeBSD, if it matters, any other OS specific solutions are also welcome.
5
votes
0answers
622 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 ...
2
votes
2answers
152 views

Why I have two /dev/sdx entries with a single disk?

In my laptop (running Linux) I have only one SSD, connected to the SATA3 port. Why I have two sdx entries in /dev directory? In particular I see /dev/sda and /dev/sdb, and /dev/sda is the SSD: # ...
8
votes
2answers
6k 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 ...
4
votes
2answers
4k views

Prevent usbhid from claiming USB device

Directly related: Prevent claiming of novelty usb device by usbhid so I can control it with libusb? I want to access an RFID reader (works as HID device) from a program that uses libusb-0.1. In the ...
9
votes
3answers
7k views

Mount printers at /dev/usb and still use CUPS

Due to a new version of CUPS, I suddenly lost the direct path to my printers that was previously available under /dev/usb/lpXXX. I used this to print directly from the command line. echo "test" > ...
6
votes
2answers
5k views

What causes /dev/disk/by-label to be populated?

I've noticed that Linux distributions typically have a /dev/disk/by-label directory, but this isn't always the case (For example, the CirrOS Linux test image doesn't have one). What's required on a ...
4
votes
0answers
2k views

How do I find out the device node corresponding to my device in SuSE 8?

I'm forced to work with a bunch of point-of-sale systems running SuSE 8. They are my client's computers. We are stuck dealing with these old systems until they get to upgrade their whole fleet to SLE ...
2
votes
1answer
637 views

Why are there symlinks in /dev? (LVM)

[root@SERVER ~] ls -la /dev/vg/root lrwxrwxrwx 1 root root 17 2012-10-28 10:29 /dev/vg/root -> ../mapper/vg-root [root@SERVER ~] QUESTION: Why are there symlinks? Why there couldn't be only 1 ...
3
votes
3answers
737 views

Disk size management

I am using Fedora 16. My /dev/sda2, mounted on / (root) with something like 50G got filled 100%: [foampile@~ 13:13:39]> df Filesystem 1K-blocks Used Available Use% Mounted on rootfs ...
3
votes
1answer
75 views

Is 'device' synonymous with 'drive' in Unix-like OS's?

In Unix/Linux terminology, are the words 'device' and 'drive' synonymous?
2
votes
1answer
309 views

Why slowusb and scandelay?

I'm running linux-3.4.9 compiled with genkernel, and booting from a USB HDD. I was slightly annoyed by the slow boot process, in particular, during the execution of genkernel scripts at the modprobe ...
2
votes
2answers
829 views

Chroot Risks w/ /dev and /proc

I am planning to set up a few chroot jails for some users to run/test Java applications (lets just assume each application is untrusted). Is there any risk involved with mounting /dev and /proc into ...
9
votes
1answer
769 views

What happens when I do “cat debian.iso > /dev/sdX”?

I'm creating a live-USB and don't understand precisely: what happens when I copy a file (or even a file system) directly to a device node (as opposed to a file system)?
5
votes
1answer
153 views

Does the suid bit have any meaning for device files?

Does the suid bit have any special meaning for device files in Linux ?
3
votes
0answers
296 views

How to know the event by looking at /dev/input/by-id

I want to access the keyboard device driver. I usually accesses it by looking at /dev/input/by-name but the event provided by it gets changed every time I log in. After searchin on the Net, I found ...
5
votes
2answers
2k views

How does /dev/fd relate to /proc/self/fd/?

$ 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 ...
10
votes
1answer
7k views

Understand output of `udevadm info -a -n /dev/sdb`

I plug an external HDD into my laptop. I try to find out the information by $ udevadm info -a -n /dev/sdb Udevadm info starts with the device specified by the devpath and then walks up the chain of ...
3
votes
1answer
513 views

FreeBSD: Remove symlinks in devfs

Background I have been rebuilding a small home NAS. This server represents my first 'real' foray into the world of server administration and it has taught me quite a bit already. Originally, the ...
9
votes
1answer
1k views

What driver is behind a certain device file?

Given a device file, say /dev/sdb, is it possible to determine what driver is behind it? Specifically, I want to determine what driver my storage devices are using. fdisk -l lists 2 devices: /dev/sda ...
1
vote
1answer
367 views

Do I need ephemeral storage?

I was running a small instance on Amazon EC2. I'm trying to migrate it to a micro as it requires very minimal processing power. One thing I just learned though, is that micro instances do not come ...
2
votes
0answers
60 views

Limiting write rate of a device

How does one go about limiting the write/read rate of a device, E.G., USB drive, SD card? Motivation behind this question is covered here (superuser.com).
3
votes
2answers
499 views

Choosing a device name under /dev from the kernel command line

I am booting CentOS via a USB install. The boot method is simply booting the ISO from GRUB2 installed on the USB Key. The USB key always gets the "name" /dev/sda. Can I change that name from the ...
1
vote
0answers
113 views

“nopage” method for ISA vs PCI [closed]

This is with reference to LDD3 ch. 15, section "Mapping memory with nopage". I am having trouble understanding the third paragraph on page 429. It says: Note that this implementation works for ISA ...