Everything about UNIX kernels: development, configuration, compilation, design, etc.

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2
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2answers
72 views

How to return 0 if a pattern is matched from a file? [duplicate]

I have a binary that repacks android kernel (not mkbootimg). I'm making a script to automate the process. I don't want any output on the screen. So I have redirected the output to a file named ...
2
votes
0answers
41 views

Can I masquerade a kernel uevent?

What I think happens From my understanding this is what happens when I connect a USB device to my computer: Kernel recognizes that I plugged in a USB device Kernel setups the very low-level things ...
3
votes
2answers
5k views

Kernel Panic - not syncing: VFS: Unable to mount root fs after new kernel compile

So I've been at this for a while and have been poking around for an answer for a few days, and figure it's about time to ask for help. I am running Ubuntu 10.10 in VMWare Fusion, and have downloaded ...
3
votes
1answer
115 views

Output shutdown messages to multiple consoles

I have configured my system to direct console output on boot to serial and vga using kernel parameters. Serial is the last argument in the kernel parameters and will be the default used for ...
2
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0answers
444 views

Install rtl8188etv/rtl8188eu driver on Orange-Pi

I'm trying to install the wifi driver on Orange-Pi board. The real chip is rtl8188etv but the driver is the same. I have compiled 3.4.105+ Kernel to have the headers: mkdir ...
0
votes
1answer
155 views

ubuntu Kernel panic while installing CentOS 7 in VirtualBox

I have a laptop with Xubuntu desktop 14.10 , and I installed VirtualBox and updated it to the latest version . I'm trying to install CentOS 7 (source downloaded from the official site) as a VM, ...
2
votes
0answers
42 views

View syscalls/kernel activity for I/O from a running process

I'd like to be able to view syscalls or kernel activity for a process...I'm not actually sure of the terminology I need here! Specifically I'm looking for the difference between I/O going to local ...
2
votes
1answer
42 views

What is /proc/filesystems supposed to be and why is it different from /lib/modules/linux_ver/kernel/fs?

The very little documentation about /proc/filesystems says it is a "list of supported file systems". I see a lot of file system modules in /lib/modules/linux_ver/kernel/fs, most of which do not appear ...
1
vote
1answer
73 views

Missing kernel headers, but need them to install the Wifi driver

I am trying to install Kali on my Lenovo Yoga13, but after formatting the disk the setup failed to install grub because of no internet access (no Ethernet, need driver to get Wifi to work). So, I ...
4
votes
2answers
2k views

Sign a module after kernel compilation

I've built a kernel in tmpfs, then I rebooted. Now I see a message when I compile the 3rd party module, NO SIGN [M] XXXX.ko How can I get it signed? The key pair generated during rpmbuild is lost ...
1
vote
1answer
73 views

Cannot update new kernel for CentOS 7 although the server have space enough

I try to update kernel on my CentOS 7 but the yum say there is no space enough on /boot although /boot have 343 MB as show below: Filesystem Size Used Avail Use% Mounted on /dev/sda2 477M 105M 343M ...
12
votes
2answers
847 views

Is it good to have multiple version of Linux Kernel?

Once, I was installing some kernel patches & something went wrong on a live server where we had hundreds of clients. Only one kernel was there in the system. So, the server was down for some time, ...
3
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2answers
400 views

How does a bootloader and kernel interact after the kernel is loaded in memory?

I'm a little bit confused about the role of bootloader and its interaction with kernel, especially when talking wrt ARM Llnux. Once the Kernel is loaded into RAM, is there any job left for the ...
1
vote
1answer
80 views

How to manually compile Fedora 20 kernel

I am trying to recreate an environment for debugging purposes. I require Fedora 20 specific kernel version (in this case its 3.17.7-200.fc20.x86_64). I have manually compiled vanilla kernel (3.17.7) ...
1
vote
1answer
98 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 ...
1
vote
2answers
7k views

Partition table not recognized by Linux kernel

I experience relatively often that the partition table of a USB stick or SD card is suddenly no longer recognized by the kernel while (g)parted and fdisk still see it, as do other systems. I can even ...
3
votes
1answer
81 views

bash runs out of memory

This question is a fork of this SO question. Here is the MCVE version: $ PS1='Parent-$ ' Parent-$ type seq seq is /usr/bin/seq Parent-$ bash $ PS1='Child-$ ' Child-$ for i in $(seq 1000000000); do ...
58
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5answers
31k views

What are high memory and low memory on Linux?

I'm interested in the difference between Highmem and Lowmem: Why is there such a differentiation? What do we gain by doing so? What features does each have?
0
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0answers
54 views

Using DKMS, to automatically patch and install kernel on update

I have a system that needs patching a file in kernel to work properly. The system is running Ubuntu 14.04. The patch patches a file in drivers/hwmon. So after every kernel update I need to download ...
0
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0answers
88 views

Avoid Booting Fedora in Failsafe Mode

I recently bought a Lenovo G50-45 and managed to setup a dual boot system with Windows 8.1 and Fedora 21 (UEFI booting). But when I boot Fedora, the following error message shows up: [1.079848] EFI: ...
2
votes
1answer
219 views

Can the hard drive timeout be disabled in Linux (attempting task abort)

Unfortunately, when a hard drive (usually a virtual drive) is slow, Linux aborts requests to that drive after a timeout, possibly causing data corruption. Last time this happened to me, I had 2 vms ...
0
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0answers
66 views

Linux Kernel Panic and Problem with boot

I have installed CentOS 6.4 on VmWare Workstation (Win 8 as Host OS). I worked with it for several days, but suddenly when I rebooted it, it did not boot properly and on stopped with this error : ...
3
votes
0answers
98 views

How to prevent kernel or any broadcast messages from flooding the TTYs?

Because of some hot-plugging issue, similar to what talked of here, the TTY displays show a continuous stream of messages (which are also logged in the /var/log directory). Every text I key in flows ...
0
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0answers
987 views

nl80211 not found

Environment Linux 3.0.8 compiled for ARM FriendlyARM mini210s I cross-compiled iw for an ARM board (friendlyARM mini210s), when I installed the utility and ran it, I got this message: # iw --help ...
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0answers
23 views

Investigating Active MemInfo

I am seeing high Active usage when I do a cat /proc/meminfo : MemTotal: 65965328 kB MemFree: 51640992 kB Buffers: 1050332 kB Cached: 8516112 kB SwapCached: 0 kB Active: 11512732 kB Inactive: 1878028 ...
0
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1answer
143 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 ...
0
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2answers
325 views

How to properly build a minimal FreeBSD kernel?

Is there any proper way to build a minimal kernel for FreeBSD? The FreeBSD Handbook has the lack of information about this. By default /boot/kernel directory has the pretty big size - around 450MB. I ...
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votes
1answer
32 views

Is it neccessary for me to update my kernel? And how? [closed]

I'm trying to install Kubuntu on a VM in order to do some deep learning following this guide: https://github.com/BVLC/caffe/wiki/Ubuntu-14.04-VirtualBox-VM I'm stuck in the step of the guide that ...
0
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0answers
105 views

No brightness control for opensuse 13.2?

I have posted on brightness issue Here!! After upgrade to KDE 5 Now i cannot change brightness through controls !! AND ALL FUNCTION KEYS (wireless,brightness,touchpad,sound +/-) are not working ...
4
votes
2answers
13k views

Command to install linux headers fails

I need to install my linux headers for an Nvidia driver install. But I get an error when doing so: peter@peter-deb:~$ sudo apt-get install linux-headers-$(uname -r) Reading package lists... Done ...
0
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0answers
56 views

Syslog message “rt_bind_peer(0) @ffffffffa0283f57”, twice in every second

My /var/log/syslog on a Debian server is flooded with lines similar to: Dec 23 16:05:40 server1 kernel: [ 686.957585] rt_bind_peer(0) @ffffffffa0283f57 These messages occur up to twice a second ...
20
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3answers
22k views

disable transparent hugepages

We are installing SAP HANA in a RAID machine. As part of the installation step, it is mentioned that, To disable the usage of transparent hugepages set the kernel settings at runtime with echo ...
0
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1answer
32 views

Does iptables protect from kernel vulnerabilities? [closed]

I read a lot of kernel vulnerabilities which are beyond my understanding. I would like to reduce the risk of an issue related to one. If I block everything other than SSH on a server, will this help ...
-1
votes
1answer
42 views

Is the kernel version fixed within the life of a release/version of each Linux distribution?

I read the Table of versions of List of Ubuntu releases. I found that the kernel version for each release is fixed. E.g. the kernel is 2.6.24 for Ubuntu 8.04, 2.6.32 for 10.04, 3.2+ for 12.04, and ...
2
votes
2answers
66 views

Why is userspace slower than the kernel?

I've heard that FUSE-based filesystems are notoriously slow because they are implemented in a userspace program. What is it about userspace that is slower than the kernel?
12
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3answers
13k views

How to disable USB autosuspend on kernel 3.7.10 or above?

I've updated my HTPC from kernel 3.7.10 to 3.10.7 and it seems CONFIG_USB_SUSPEND is now gone from the kernel options and included in PM. The main problem I'm facing is that I have an external HDD ...
4
votes
1answer
65 views

what's the difference between page cache and buffer cache?

In linux OS, you can type command "echo 3 > /proc/sys/vm/drop_cache" to release memory, and you can type command "sync" to release the memory. And in linux kernel there are two kind of cache, one is ...
0
votes
1answer
54 views

Custom Kernel to Disable SATA and USB Devices

I am setting up diskless clients that will run on an internal network. I have disabled SATA and USB ports using a BIOS locked with a password, but this is easy to get around by using the jumper to ...
1
vote
2answers
70 views

Is system call the only way that a user program can intentionally affect the state of a Linux kernel?

I think there are several ways that a user program can intentionally affect the state of a Linux kernel. By invoking a system call; By invoking mmap() and writing the memory that has been mapped to ...
0
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2answers
100 views

When building a new kernel in OpenBSD 5.6, can the name of `config` be something else?

I am using the release version of OpenBSD 5.6 and have to apply a patch called 004_kernexec.patch.sig (URL: http://ftp.openbsd.org/pub/OpenBSD/patches/5.6/common/004_kernexec.patch.sig ) An excerpt ...
6
votes
1answer
189 views

Some basic questions about Linux kernel's security [closed]

I don't know much about Linux kernel, and I have some questions. What is the main purpose of separating kernel memory from user-space memory? To make sure that a user application cannot do anything ...
1
vote
1answer
166 views

iwlwifi: timeout delays firmware to be loaded

I'm using OpenSuSE 13.2 beta (which runs by the way very nicely). When starting up, my wireless adapter (Intel Centrino Ultimate-N 6300 AGN/Thinkpad T420) delays about one minute... But then it works ...
0
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0answers
72 views

different ways how Linux TCP/IP stack terminates connection

I have a Linux machine which connects to SSH server with SSH client(OpenSSH_4.1p1). SSH client machine has IP address 10.10.11.1 and SSH server has IP address 10.10.10.1. SSH client has kernel version ...
8
votes
2answers
7k views

How does the Linux kernel handle shared IRQs?

According to what I've read so far, "when the kernel receives an interrupt, all the registered handlers are invoked." I understand that the registered handlers for each IRQ can be viewed via ...
1
vote
1answer
33 views

take the DRAM performance of the processes into consideration when scheduling

The CFS scheduler in Linux schedules the processes based on the virtual runtime of CPU. But, the DRAM memory is the bottleneck in most of the emerging domains. Why not take the DRAM performance of ...
0
votes
3answers
820 views

swap partition and its laws

I remember for choice of swap partition, we should use (swap > 2xRAM) at least.Of course it deprecated , because max of computer's ram is very high. kernel support it. My question: i remember each ...
0
votes
1answer
414 views

psmouse sync issues!

I have Compaq CQ61-420US (64-bit AMD) laptop with Synaptics touchpad checked using $ egrep -i 'synap' /proc/bus/input/devices N: Name="SynPS/2 Synaptics TouchPad" But recently after Arch Linux ...
0
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1answer
31 views

Disallow change of init kernel parameter

is there any way to disallow changing init parameter on boot time? I want to prevent situation when someone reboot my server, edit grub entry and get access without password. Maybe some kernel ...
5
votes
1answer
1k views

get kernel source code

I need a specific kernel version to compile it with some additional modules. When I typing: uname -r I get 3.8.0-29-generic I need this one. uname -a Linux "..." 3.8.0-29-generic ...
2
votes
1answer
33 views

does the second kernel need kexec enabled

It's clear that you need the kexec syscalls in the 'first' kernel. But does the kernel that should get loaded (with kexec_load and reboot) need to be compiled with kexec? If yes, what extra code ...