The devices tag has no wiki summary.
23
votes
7answers
44k views
How do I find out what hard disks are in the system?
I need to know what hard disks are available, including ones that aren't mounted and possibly aren't formatted. I can't find them in dmesg or /var/log/messages (too much to scroll through). I'm hoping ...
21
votes
1answer
780 views
What do the device files in /dev actually do?
(Not a duplicate of Understanding /dev and its subdirs and files)
I was browsing around my filesystem and for the first time I took a second to analyze my /dev directory. I was surprised by the ...
18
votes
2answers
856 views
Why are network interfaces not in /dev like other devices?
I'm mostly curious, but why aren't network interfaces in /dev?
Are there any other kinds of devices that aren't represented as a node under /dev?
16
votes
2answers
1k views
How to create /dev/null?
I successfully deleted my /dev/null. How can I restore it? The OS is Ubuntu.
16
votes
4answers
6k 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 ...
14
votes
2answers
978 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:
...
12
votes
3answers
1k 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.
11
votes
2answers
2k views
Manipulating `/dev/video`
I'd like to take the video stream from /dev/video0, apply some effects or changes and make the result available on /dev/video1.
/dev/video0 ---> Apply Effects ---> /dev/video1
For example, mplayer ...
10
votes
4answers
2k views
Can I setup a loopback audio device?
If I can send audio to the output devices, then I can record the same audio as a wave. With filesystems, you can just setup a loopback filesystem and write binary data on a file instead of a device.
...
9
votes
1answer
443 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)?
9
votes
3answers
2k views
Shell command to read device registers?
On a single-board computer running Linux, is there a way to read the contents of the device configuration registers that control hardware? I think it would be a wrapper for inw(), more or less.
I'm ...
8
votes
2answers
982 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, ...
8
votes
3answers
2k 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" > ...
7
votes
2answers
435 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 ...
6
votes
3answers
3k views
Find out what device /dev/root represents in Linux?
On linux, there is a /dev/root device node. This will be the same block device as another device node, like /dev/sdaX. How can I resolve /dev/root to the 'real' device node in this situation, so ...
6
votes
2answers
3k views
How do mouse events work in linux?
This is mostly out of curiosity, I'm trying to understand how event handling works
on a low level, so please don't reference me to a software that'll do it for me.
If for example I want to write a ...
6
votes
3answers
2k views
If I connect a physical device, how can I ever know which device file belongs to it?
Say I plug in several USB drives which don't get automatically mounted. How can I find out which device file belongs to which physical device, so I can mount it for example?
I'm running Mac OS X but ...
5
votes
3answers
396 views
How to get my USB key to auto mount
I'm currently working in a command line only environment.
When I plug my USB key in, I see a new device file in /dev:
...
sdi
sdi1
...
If I simply sudo mount /dev/sdi1 /media/tmp, and umount it ...
5
votes
3answers
544 views
Questions about mount and device
Please bear with my following questions.
What is the difference between /dev,
/media and /mnt? Following is what I
have found from internet but I still
have little idea:
/dev this folder ...
5
votes
3answers
1k 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 ...
5
votes
2answers
219 views
How does cat know the baud rate of the serial port?
I regularly use cat to view debugging information in the console from my FPGA development board over the serial connection, but I never have had to tell linux what the baud rate is. How does cat know ...
5
votes
4answers
250 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 ...
5
votes
1answer
2k 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 ...
5
votes
1answer
212 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 ...
5
votes
1answer
595 views
How to be notified when a USB device was plugged?
My system have to auto-mount for usb devices, how can I be notified when a usb device is plugged? Where can I read more about?
I would like to treat that using shell script or C.
5
votes
1answer
107 views
Does the suid bit have any meaning for device files?
Does the suid bit have any special meaning for device files in Linux ?
5
votes
2answers
884 views
How can I create a direct 8khz audio pipe in Ubuntu?
I'm interested in creating musical programs like these:
http://www.youtube.com/watch?v=GtQdIYUtAHg&feature=player_embedded
Essentially these programs just generate sequences of integers, which ...
5
votes
2answers
267 views
Unclaim a device
So I am using Ubuntu and trying to use some hardware which I had some problems with before.
The problem before was that the company who made my hardware sold their internal parts to another company ...
5
votes
1answer
230 views
Does the kernel delete entries in /dev on an initramfs?
I have a fully custom, minimal, embedded Linux (vanilla, 3.3.8, i486, Vortex86dx) system that boots from an initramfs image. No standard distribution scripts are used, just a single rcS file that does ...
4
votes
2answers
400 views
What’s the difference between a “raw” and a “cooked” device driver?
Does this concept only apply to terminal drivers (which is what most sites cover) or to any driver in general?
4
votes
2answers
3k 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 ...
4
votes
3answers
1k views
What do first column in /proc/mounts really mean in Linux?
Run cat /proc/mounts and I get this (simplified):
rootfs / rootfs rw 0 0
proc /proc proc rw,relatime 0 0
/dev/sda1 / ext3 rw,relatime,errors=continue,barrier=1,data=ordered 0 0
io /etc/blkio cgroup ...
4
votes
1answer
77 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, ...
4
votes
2answers
46 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 ...
3
votes
1answer
265 views
Writing /dev/random to file?
If you ran the following, what would happen?
cat /dev/random > ~/randomFile # don't run
Would it be written until the drive runs out of space, or would the system see a problem with this and ...
3
votes
4answers
1k views
GNU/Linux (Debian): detecting hard-disks mappings?
Let's suppose you have two hard-disks:
one internal (boots GNU/Linux);
one external (USB).
"fdisk -l" detects both, but will not tell you which is /dev/sda and which is /dev/sdb. "lsusb" will tell ...
3
votes
2answers
1k views
Can I share a device from under /dev across hosts?
Here's the situation. I have a video device /dev/video0 on a VMware Server and I want to access this device from within a virtual machine. However for whatever reason I can't connect the device ...
3
votes
1answer
2k 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 ...
3
votes
3answers
58 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
1answer
199 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 ...
3
votes
1answer
209 views
How do I setup more then 10 loopback device?
From this answer the solution is to
modprobe loop max_loop=64
Which makes me allowed to use 64 loopback devices then
mknod -m 660 /dev/loop8 b 7 8
To create the devices. I did this for 8, 9, 10 ...
3
votes
3answers
2k views
Prevent claiming of novelty usb device by usbhid so I can control it with libusb?
I have a USB rocket launcher that I wish to experiment with through libusb. However, libusb cannot claim the interface; presumably because the output of usb-devices lists 'usbhid' as the driver for ...
3
votes
2answers
95 views
How to grant non-root user access to device files
I have device file that appears in /dev when a specific board is plugged in. The read and write operations to it work just fine, but in order to open the device file the program needs to be executed ...
3
votes
2answers
52 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?
3
votes
2answers
45 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 ...
3
votes
1answer
292 views
Vanishing permission on device file (RHEL 6.1)
I want to set world read/write permissions on a raw block device file (yeah, I know). I can set the permission to 666, but it goes back to 660 immediately after I touch it or write to it. Why?
...
3
votes
1answer
1k views
/dev/sdb: No such file or directory (but /dev/sdb1 etc. exist)
I'm not sure what is wrong here but when running fdisk -l I don't get an output, and when running
fdisk /dev/sdb # I get this
fdisk: unable to open /dev/sdb: No such file or directory
I'm ...
3
votes
2answers
745 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 ...
3
votes
1answer
277 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 ...
3
votes
1answer
934 views
Change the number of generated /dev/tty devices
I'm building an embedded Linux system, based on Gentoo. Using udev, all tty devices are probed with a PROGRAM stanza to determine if they are a modem.
Right now the system boots up with 64 /dev/tty*. ...
