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54
votes
7answers
37k views

How can I see dmesg output as it changes?

I'm writing a device driver that prints error message into ring buffer dmesg output. I want to see the output of dmesg as it changes. How can I do this?
31
votes
3answers
4k views

Why is dmesg called dmesg?

Is there any explanation/history behind the name of the command dmesg (which prints out some kernel messages)?
16
votes
4answers
8k views

How can I write to dmesg from command line?

I'd like to write a statement to dmesg. [How] can I do this?
10
votes
2answers
10k views

Human readable dmesg time stamps on OpenWRT

The output of dmesg shows the number of second+milliseconds since the system start. [ 10.470000] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver [ 14.610000] device eth0 entered ...
10
votes
3answers
17k views

How can dmesg content be logged into a file?

I'm running a Linux OS that was built from scratch. I'd like to save the kernel message buffer (dmesg) to a file that will remain persistent between reboots. I've tried running syslogd but it just ...
9
votes
1answer
2k views

Where does the kernel ring buffer sit relative to rsyslog?

Is rsyslog just an abstraction layer on top of the kernel ring buffer? Or is the kernel ring buffer its own entity and rsyslogs interaction is like that of any other "application"?
8
votes
2answers
56k views

command to determine ports of a device (like /dev/ttyUSB0)

I have a question regarding the ports in Linux. If I connect my device via USB and want to check its port I cant do it using the command lsusb, which only specifies bus number and device number on ...
8
votes
3answers
419 views

decrease kernel boot log verbosity level

When my kernel boots, apart from the useful important information, it prints lots of debugging info, such as .... kernel: [0.00000] BIOS-e820: [mem 0x0000000000000000-0x000000000009d3ff] usable ...
7
votes
1answer
1k views

Difference between output of dmesg and content of /var/log/dmesg?

I found the output of dmesg and content of /var/log/dmesg are different. Then what differences are between their purposes?
5
votes
2answers
5k views

How to read dmesg from previous session? (dmesg.0)

dmesg is a command to read the contents from /var/log/dmesg. The nice thing compared to less /var/log/dmesg is that I can use the -T flag for human readable time output. Now I would like to look at /...
5
votes
1answer
131 views

USB drive offline in dmesg and ? in ls, but only for some files?

I have a backup drive that has been intermittently failing (but almost always succeeding) to run rsnapshot lately. ls and e2label output are not encouraging: $ ls -al /mnt/backup/ ls: cannot access /...
4
votes
1answer
4k views

How to know what to grep for in dmesg?

I recently had some trouble with a wireless card, and an online forum suggested searching dmesg with grep firmware. That helped, I was able to find the problem immediately! However, the previous hour ...
4
votes
1answer
225 views

dmesg email digest

I have a remote server which has some issues (Seem hardware related) which means that it logs KVM errors and then sometime later it becomes unresponsive and locked up. There is an often an early ...
4
votes
2answers
901 views

Why and how to track /var/log/dmesg with version control

On this wiki they recommend tracking /var/log/dmesg using Mercurial. I wanted to set up a cron job on CentOS 6.4 like on this page to remind myself to make commit messages for such a repo. However, ...
4
votes
2answers
2k views

dmesg: pci BAR 7: can't assign io

I have VMware virtual machine running Debian Wheezy. I have compiled my own kernel 3.14. I have noticed dmesg is flooded with messages pci BAR 7: can't assign io (size 0x1000). I have no idea what ...
4
votes
1answer
2k views

USB device messages flooding dmesg (and console)

When USB mouse is plugged into my laptop, dmesg is flooded with following messages: usb 3-1: USB disconnect, device number 28 usb 3-1: new low-speed USB device number 29 using xhci_hcd usb 3-1: New ...
4
votes
1answer
153 views

How to exclude auditd messages from dmesg and only log them in /var/log/audit.log

I use audit to log suspicious user actions on a workstation in my institution. I found that, in addition to logging to /var/log/audit.log, auditd also writes to /var/log/messages. Consequently, ...
3
votes
1answer
259 views

What do the fields in the libata device probe line in dmesg mean?

When the kernel boots, it prints out lines like this for each SATA device: [ 0.919450] ata2.00: ATA-8: ST2000DM001-1CH164, CC24, max UDMA/133 [ 0.919487] ata2.00: 3907029168 sectors, multi 16: ...
3
votes
2answers
47 views

How can I activate extra-verbose mode (debugging mode) during Debian boot?

How do I activate extra verbosity during boot, on Debian? I removed the quiet parameter and tried to add debug but it didn't help. My problem is that my keyboard takes 2-3 min to activate so it ...
3
votes
2answers
2k views

Mount an USB: dmesg shows nothing

I'm trying to mount a USB-drive. However, it seems that my Linux (Debian) doesn't recognise it at all (and any other usb-drive), though it powers it. The usb-hubs are OK, because I was able to boot ...
3
votes
1answer
52 views

change log format for dmesg

I am getting my dmesg messages like this, [ 27.154743] uvcvideo: Found UVC 1.00 device Integrated_Webcam_HD (0c45:6a04) [ 27.194956] usbcore: registered new interface driver uvcvideo But, I ...
3
votes
1answer
757 views

How can I stop “Timed out waiting for forcewake old ack to clear”?

Running Arch Linux with Intel i915 and onboard Intel graphics. If I do a dmesg, I get line after line of "[drm:__gen6_gt_force_wake_mt_get] ERROR Timed out waiting for forcewake old ack to clear". ...
3
votes
2answers
172 views

How to test whether Linux is running on a ThinkPad?

I need to programmatically detect if Linux is running on a ThinkPad. A shell script would be ideal but I can programmatically generate any binary by downloading some source and compiling it on the ...
3
votes
1answer
26 views

Bluetooth BNEP takes a long time to load on boot Debian

My system takes a long time to boot and looking at dmesg output I found an entry with BNEP (Ethernet Emulation) ver 1.3 that takes around 27 seconds to load. Does anyone have a clue on how to speed ...
3
votes
0answers
376 views

How to debug ACPI/poweroff problems?

I recently replaced my hard drive with a Sandisk SSD and did a fresh install of Fedora 21 (previously using F20). Now my laptop won't power off, and I'm not sure which of the two is causing the ...
3
votes
1answer
504 views

can't filter printk messages

I'm writing a driver and usually I implement my own log-level scheme. However, this time I figured that I would try to utilize the printk scheme that is built into Linux. I see that I can adjust the ...
3
votes
0answers
252 views

Virtual kernel memory layout in dmesg linux kernel 2.6.31

I'm working on a embedded linux project for ARM architecture, kernel version is 2.6.31.12-rt21. In dmesg, I cannot see the virtual kernel memory layout like this: virtual kernel memory layout: ...
2
votes
1answer
34 views

Tweak perl script for human-readable dmesg output

In RHEL 6 I have the kernel parameter: printk.time=1 So that my dmesg would have a timestamp. However it shows in seconds from restart, like this: [12.23456] I found a script that you place ...
2
votes
2answers
778 views

Interpreting output of dmesg and /var/log/boot.log

I found two ways for printing boot messages one using dmesg and another the content of file /var/log/boot.log: The content of the /var/log/boot.log file are: fsck from util-linux 2.20.1 /dev/loop0:...
2
votes
2answers
321 views

How can I find the text show in the screen when linux boot? That's not the same as dmesg shows

When gnu/linux boot message shows, that's not the same as dmesg shows. How can I find it back?
2
votes
1answer
1k views

What is MCH_SSKPD warning in dmesg?

While i was reading dmesg log just to check that everything is fine, i met [ 18.956187] [drm] Wrong MCH_SSKPD value: 0x16040307 [ 18.956190] [drm] This can cause pipe underruns and display ...
2
votes
1answer
5k views

How do I read the output of `dmesg` to determine how much memory a process is using when oom-killer is invoked?

I asked this question: Running `sudo /sbin/service mysqld start` causes system to crash In the comments of one of the answers, a very helpful individual is asking for more information regarding how ...
2
votes
1answer
141 views

ifup wlan0 causes kernel Oops

on my laptop, when I do ifup wlan0, sometimes I get following call trace in dmesg. Other times, the log looks perfectly normal, and there are no kernel Oops messages. In both cases (with errors and ...
2
votes
3answers
2k views

dmesg filled with audits every minute from cron

My dmesg is filled with output of like the following, starting from a couple of seconds after booth and continuing indefinitely: [ 3155.216230] type=1006 audit(1393236841.859:85): pid=4206 uid=0 old ...
2
votes
1answer
4k views

Which drive had a “journal commit I/O error”?

I received a message: kernel:[123456.789012] journal commit I/O error Which disk drive had the journal error?
2
votes
1answer
62 views

What is the appropriate pronunciation of the “dmesg” filename? [closed]

How should the file dmesg (as in /var/log/dmesg) be pronounced? I've always pronounced it as "dee message" but received an odd reaction from a Unix admin when I did that.
2
votes
1answer
280 views

Slow root / mounting time

By running dmesg -t -d on my Raspbian/Debian Jessie, I see that this is a bottleneck in my booting process: [< 4.777880>] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. ...
1
vote
2answers
44 views

Making sense of Time in dmesg

I know the time in dmesg is the time since boot. But my specific question is this time is calculated at the start or end of the process mentioned in the line? Why this is important? take this example:...
1
vote
1answer
3k views

What's the difference between 'no caching page mode present' and 'assuming drive cache. write through.'

Post-POST, post-BIOS screen, post-GRUB; when I boot Debian with a SD card or USB stick plugged in, one of the first things to pop up on the screen (so quickly that usually I don't even notice) looks a ...
1
vote
2answers
95 views

How to print kernel time from command line?

How can I convert the uptime output to seconds since epoch to compare with dmesg output? Does uptime have the same resolution as the kernel message time? Is there a way to more directly get the ...
1
vote
2answers
68 views

About how many lines come up when booting a typical Linux distro?

I'm trying to understand all the text that screams by when my server boots up. Is that really intended to be human readable? About how many lines scream by? Is there a way I can count them? Is ...
1
vote
1answer
377 views

Where in the kernel /dev/kmsg gets initialized?

I'm trying to figure out at which point in the boot up process /dev/kmsg gets initialized and can thus be written. On my system the first line that occurs in dmesg is printk(KERN_INFO "Initializing ...
1
vote
1answer
190 views

Force mounting, bypassing fsck

When I try to mount some SD card, it fails and dmesg displays: [ 124.121735] FAT-fs (sdb1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck....
1
vote
3answers
2k views

Log message “Disabling IRQ”: what does it mean?

This message appears in my dropdown terminal at seemingly random times when no processes is running in that terminal: andreas@debianator:~$ Message from syslogd@debianator at Feb 24 18:57:58 ... ...
1
vote
1answer
170 views

Clunking hard drive, some info appears in dmesg but none in fdisk -l, what are my options?

I've been backing up old IDE hard drives onto a new USB drive this afternoon. One, a 2002 120gb Western Digital, has been a bit of a problem. I have connected it (as with the other hard drives) to ...
1
vote
1answer
80 views

Wifi stopped working, “Unknown symbol wireless_nlevent_flush”

As of this afternoon the wifi on my Dell XPS 13 stopped working (running Debian sid with kernel 4.4.0-1-amd64). lspci detects my wifi card, but ifconfig -a shows only the loopback interface. I tried ...
1
vote
1answer
1k views

No ttyUSB when connecting USB-RS485 to Beaglebone Black

I'm trying to connect a externally powered board to control the motors of a robot to my BeagleBone Black. I'm using ssh over USB(the mini-usb) to control the Beaglebone from my laptop. The BBB is ...
1
vote
1answer
560 views

TT-Connect CT2-4650 CI doesn't initialize (Timeout?)

I've tried to get a Techno Trend TT-connect CT2-4650 CI running under a Kali Linux, where I suppose the kernel is about the same as on a current Debian. The compilation ran just fine. The kernel ...
1
vote
1answer
2k views

How to avoid overflowing the kernel printk ring buffer?

I'm trying to debug a linux driver and a particular piece of code is behaving very strangely. In order to see what's going on I've filled the code with printk statements so I can see exactly what the ...
1
vote
0answers
50 views

Can't get usb ethernet adapter running under CentOS 6 minimal

I have a cheap usb adapter and using it on a minmal CentOS 6.7 box, when I plug in the adapter it's recognized as usb device but not as ethernet adapter, although I've loaded these kernel modules: ...