The kernel of operating systems popularly known as Linux, or sometimes GNU/Linux.

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Can a kernel preemption happen in the process context with `TASK_INTERRUPTIBLE` state?

If a process sets itself to the sate of TASK_INTERRUPTIBLE, can it be preempted by other kernel components? If it does, I think this process maybe lost wake-up chance due to failed to check the ...
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3answers
83 views

Legal status of an embedded Linux case

I wanted to find the source code of embedded Linux that is used in Shenzhen Apexis Electronic Co.,Ltd products. For example in this page: http://apexis.com.cn/productsdetails_244.html You see they ...
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39 views

How to Induce read-only to Linux filesystem?

I've read in several places that during an I/O error to the system log file most Linux distributions go to read-only mode. They followed with a procedure for how to recover from it. This is all fine, ...
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1answer
272 views

4G modem on an embedded 2.6.32.9 kernel on a Parrot AR Drone 2.0

I am attempting to compile support for a Huawei E3276 usb LTE modem for an embedded Linux/BusyBox installation on a Parrot AR Drone 2.0, which is based on kernel 2.6.32; however, I am running into ...
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1answer
310 views

How to get kernel messages on serial console on a systemd system?

I'm trying to set up an A20-OLinuXino-LIME2 as a headless fileserver with a Debian 8 image from Igor Pečovnik's builds. I would like the system to output its kernel messages to the serial console ...
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70 views

Linux process - messages from kernel [closed]

I have been learning about different IPC mechanisms present in Linux, for communication between user space processes. I want to ask what are various ways in Linux for the kernel to communicate with ...
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1answer
189 views

Booting encrypted disk kernel error: Cannot initialize device-mapper

I have Ubuntu 15.04 with a default full disk encryption installed on my chromebook Pixel with linux-samus kernel patch and everything is working fine. I've just tried compiling a newer version of the ...
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318 views

APEI Generic Hardware Error : PCIe error with ATTO SAS HBA

Recently we upgraded a remote server to a new Dell PowerEdge T630 with dual CPUs (so all PCIe slots are active). It had been running for several weeks fine before we added an IBM LTO5 tape drive that ...
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25 views

SystemTap log output to file

I want to log output from my SystemTap script to a file. But when I try to use the -o option like: stap -r $PWD --remote user@hostname -o test.txt -S 1 ./test.stp I can't find the log file. If I ...
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2k views

Changing the TCP RTO value in Linux

I want to alter the TCP RTO (retransmission timeout) value for a connection, and some reading I have done suggests that I could do this, but does not reveal where and how to change it. I have looked ...
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44 views

What is the register %gs used for?

All I was able to find out about the %gs register is, that it seems to be a free to use register on >32bit x86 architectures. It seems that a gs_change is executed before any system-call. Can someone ...
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85 views

Case study of virtual memory management

Need help in understanding virtual memory concept. When a process requesting for 2GB mapping onto the virutal memory in Linux environment of 4GB ( 1GB Kernel : 3GB Userspace), when already another ...
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131 views

What is the impact on system performance when kernel debug info is enabled?

In order to debug kernel or use tools like stap (https://en.wikipedia.org/wiki/SystemTap) kernel must be compiled with full debugging information included - namely option CONFIG_DEBUG_INFO has to be ...
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1answer
101 views

bluetooth - btusb module remove stops bluetooth service

I just faced a strange issue; Every time after suspend the btusb module is kicked out the RAM (for some reason but its OK cause I can reinit it manually) but as a result the bluetooth.service must be ...
2
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1answer
73 views

How does the kernel decides what pages commit to swap?

If RAM usage is higher than the level written in «swapiness», kernel will use SWAP. Ok. But how does the kernel «order» programs? Is it «first come, first served» for RAM? Or biggest programs in ...
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153 views

Kernel memory leak detection [closed]

How are memory leaks identified in Kernel. Not sure if Valgrind can be used in this case.
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Linux Angstrom can't start without serial cable plugged

I'm using the Altera Cyclone V Soc dev Kit and Linux Angstrom provides by rocketboards (http://rocketboards.org/foswiki/Documentation/GSRD141) Kernel is : 3.10 LTSI Linux can't start if any serial ...
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1answer
191 views

How do I detect that my system has auto-rebooted after a kernel panic?

I'm using Linux in embedded systems, and want to configure the system to automatically reboot after a kernel panic. However, when the system comes back up, it's important for me to detect and log the ...
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2answers
179 views

Telling Linux kernel *not* to use certain CPUs

I'm trying to run some benchmarks on a multicore machine and I'd like to tell the Linux kernel to simply avoid certain cores unless explicitly told to use them. The idea is that I could set aside a ...
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5answers
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Why is the Linux kernel called an “image”?

I often hear people refer to the Linux kernel as the Linux kernel image and I can't seem to find an answers on any search engines as to why its called an image. When I think of an image I can only ...
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47 views

Trace kernel object calls

We have strace to trace programs, ltrace for dynamic libraries, and others. Is there any equivalent for kernel objects, as in tracing just like strace but for a specific .ko? Thanks
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High %sy cpu usage , server is very slow

On one of the server we are noticing high %sy usage due to which server is very slow. Below is strace count for syscall. What will be the reason for high %sy usage. % time seconds usecs/call ...
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70 views

Arch very long boot-time after kernel downgrade

I just downgraded my arch kernel from 4.x to 3.17.x for the sake of being able to use shared folders feature in vmware. Right now, everything is fine and it boots up too. But boot-time has greatly ...
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1answer
274 views

what does it mean 'fork()' will copy address space of original process

I'm studying 'operation system concepts' on my own and I'm studying the chp3. process part. There is an example where the 'fork()' function is called and depending of the returned pid value like the ...
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63 views

Minimum required packages for a LFS/DIY-Linux system?

I am trying to make a super-minimal linux system, as a base for experimentation, and just for the experience. I have built DIY Linux (similar to Linux from Scratch) before, but I was wondering how ...
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how to find which linux kernel commit made its way to exactly which kernel version [duplicate]

We have a problem that started appearing in kernel-uek-3.8.13-68.1.2.el6uek.x86_64. Symptoms and description matches exactly this linux kernel developers description ...
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74 views

Is there a way to expose extra settings through sysfs using the IIO framework?

The driver I'm developing has a number of settings I want the user to be able to change that don't really fit into the IIO framework. For example, using the IIO_CHAN_INFO_SAMP_FREQ enum in my read ...
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292 views

routing table “220” in Linux kernel 3.2.0-23-generic

I have a Linux machine with kernel 3.2.0-23-generic and it has rule with priority 220 in RPDB which points to routing table named "220": T42:~# ip rule show 0: from all lookup local 220: ...
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749 views

routing cache in latest Linux kernels

As I understand, routing cache was removed since Linux kernel 3.6. In systems with older Linux kernel one could view the content of the routing cache with ip route show cache command and routing ...
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When a process forks is its virtual or resident memory copied?

The standard way of making new processes in Linux is that the memory footprint of (parent) the parent process is copied and that becomes the environment of the child process until execv is called. ...
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278 views

how to increase Stack Size of a running program in C

I am trying to identify any way if we can increase the stack size of my running program after getting SIGSEGV. I know we can increase the size of stack by ulimit -c but, that did not solve this ...
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51 views

Why my limit on CPU does not validate via cgroups

/etc/cgconfig.conf ... group memlimit { memory { memory.limit_in_bytes = 8589934592; } } group cpulimit { cpu { cpu.shares = 1024; } } /etc/cgrules.conf: ...
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How to enable random PIDs on Linux?

I'm currently comparing random PID implementation on OpenBSD, FreeBSD and Linux from security perspective. As long as OpenBSD and FreeBSD are concerned, my work is done. However, while the answer ...
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Understand logging in Linux

As I understand, Linux kernel logs to /proc/kmsg file(mostly hardware-related messages) and /dev/log socket? Anywhere else? Are other applications also able to send messages to /proc/kmsg or /dev/log? ...
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2answers
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Triggering hardware interrupts by connecting parallel port pins 9 and 10 does not work

I want to trigger hardware interrupts as described in the book Linux Device Drivers by connecting pins 9 and 10 with a wire. I tried that but apparently there's no interrupt beeing triggered: cat ...
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1answer
131 views

Linux doesn't drop FS Caches. Instead Memory starts Swapping

I'm quite confused about this behaviour of linux memory caching. total used free shared buffers cached Mem: 15953 14188 1765 64 ...
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2answers
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Linux does not reply to ARP request messages if requested IP address is associated with another (disabled) interface

I have a PC(kernel 3.2.0-23-generic) which has 192.168.1.2/24 configured to eth0 interface and also uses 192.168.1.1 and 192.168.1.2 addresses for tun0 interface: root@T42:~# ip addr show 1: lo: ...
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0answers
358 views

How to create Linux Kernel Headers from Linux Kernel Source?

I'm working with Tiny Core Linux and attempting to install Vmware Tools, which of course needs the Kernel Headers :-). It does not appear they have the Kernel Headers readily available in a package, ...
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How to resolve dracut problem when intall Fedora 21

I'm Ubuntu User. But I wanted to change my OS from Ubuntu to Fedora. So I wanted to Fedora 21. But there is a problem. I'm using USB Drive to boot Fedora 21. When I try to install Fedora I get a ...
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What are the programs/commands which the magic SysRq key invoke?

From Magic SysRq key The magic SysRq key is a key combination understood by the Linux kernel, which allows the user to perform various low level commands regardless of the system's state. It ...
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How SYN and ACK packets counted by the server(Linux)

I have a question about tcp layer of linux kernel. I want, Syn and ack packages received to server will be counted. where total_syn_count and total_ack_count are variables to be defined and will ...
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1answer
59 views

Do I have to publish kernel source if I release a custom kernel?

I have a kernel for an android phone ready for release. I always have the current source code already pushed to GitHub for release builds. However, I also have an experimental folder on my server ...
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107 views

SMB/CIFS mount not working with exec() call

To mount CIFS presently I use system() call in source, this works. If I try to run command manually on shell it works too. $ mount -t cifs //IP/dir /mnt -o user=name,pass=PASS,domain=mydomain,nounix ...
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1answer
645 views

Where is routing table stored internally in the Linux kernel?

When I execute route -n, from where exactly (from which structs) is the information displayed retrieved? I tried executing strace route -n but I didn't help me finding the right place it's stored.
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1answer
259 views

RHEL not booting with the updated kernel after upgrade [closed]

We have recently upgraded RHEL boxes, but the system only booted with the old kernel. Observation is that there is no link /etc/grub.conf to /boot/grub/grub.conf. Now, to boot the system with the new ...
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825 views

how to untar file in linux red hat?

I am compiling linux red hat stable kernel on red hat linux and the error which I am facing is as below
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Which linux kernel options need to be enabled to support bluetooth low energy?

Which are the mandatory and optional options?
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Kernel modules for compiled kernel

I cannot find kernel-headers. For the first time I compiled and installed the latest kernel (4.0.3) on my Debian Wheezy, and now I am trying to install ndiswrapper using module assistant. For that, ...
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Trying to use KDBG, but it produces error 11

I am trying to start kdbg on Ubuntu, but it produces this error message: MNG error 11: function is invalid at this point ; chunk MHDR; subcode 0:0 MNG error 11: function is invalid at this point ; ...
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How to read the output of the show-memory-usage SysRq?

I couldn’t find any (recent) documentation on reading the output of the show-memory-usage SysRq (Alt+SysRq+m). So what can one learn from looking at it? Here is an example output form my box (Kernel ...