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Questions tagged [kernel]

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

7
votes
4answers
611 views

Why does the kernel even bother to send SIGKILL? [duplicate]

If a program is not allowed to handle or ignore SIGKILL and SIGSTOP, and must immediately terminate, why does the kernel even send the signal to the program? Can't the kernel simply evict the program ...
0
votes
0answers
31 views

USB protocol hack [on hold]

I have a RPi 3+ b and I want to do some crazy forensics experiment, but in order to do such I require to "convert"(i use convert lightly) my USB port into a "pcie x4" port. Of course I do not mean ...
2
votes
0answers
40 views

Slow ethernet speed - Realtek RTL 8111/8168/8411

With a Windows PC connected to the same router I get normal/fast ethernet/internet speed but not with this PC which before my changes used driver r8169: Linux Mint 18.1 Serena 64 bit Kernel Linux ...
3
votes
1answer
33 views

Why are du -h / du / df / df -h not refreshing when extracting a large file

I am running tar in the background, eg: tar xfvz large_file.tar.gz & It does extract my file, but when I then launch du -h, du, df or df -h, the output remains the same, and I have to wait ...
-1
votes
0answers
24 views

Recompiling kernel to reduce vmlinuz size to less then 5-6mb

I am compiling kernel for my Ubuntu to minimal but every time i compile i am getting uuid not exists dropping to shell ERROR (if my kernel size is less then 8mb).. My minimum Size is 4.7mb but still ...
0
votes
0answers
23 views

Kernel compiling - Error during sync of the configuration

I am trying to compile the 4.19 kernel on my Linux Mint machine. I copied my current config (which is from 4.15), opened make menuconfig in order to append a local version string, saved it and then ...
-1
votes
2answers
62 views

What is the Linux Plumbing Layer? [on hold]

Can anyone please explain what is meant by the Linux Plumbing Layer in the kernel, as mentioned in the LWN.net article here? https://lwn.net/Articles/495516/ Does it mean to make a more unified ...
2
votes
0answers
23 views

Does the Linux Kernel use event-loops to keep itself alive? [duplicate]

I am just wondering what mechanism does the Linux Kernel program use to keep itself alive. Any normal C program will terminate by executing its statements sequentially. If we wanted to keep that ...
-1
votes
0answers
18 views

What issues might I face using the epel mainline kernel with CentOS? [closed]

I'm upgrading a dual processor Opteron (Abu Dhabi) to a Ryzen 2000 series processor. I understand that there seems to be a minimum retirement somewhere in the 4.x kernels for proper boost support and ...
2
votes
1answer
69 views

How essential are usernames ( compared to uids )?

Background: I recently read about a freedesktop.org-bug which allowed executing any systemctl command for uid > INT_MAX. Thus I ran: root@host$> useradd -u 4000000000 largeuiduser root@host$&...
1
vote
0answers
7 views

Enabling I2S on Qualcomm Snapdragon 820 board

I'd like to configure a Qualcomm Snapdragon 820 board for I2S communication as an I2S slave to an external codec. Currently, the board has some GPIOs that can be configured for I2S function. How can I ...
1
vote
2answers
77 views

Is it possible to hide an area of hard disk from root user?

Do linux kernel have a feature that can be used to hide an area of hard disk (e.g last 1GB of hard disk) from root user or at least make that area completely unwritable by any means?
3
votes
1answer
66 views

Does the root user have read/write access to kernel code?

I want to know if the root user can read from and write to sections of kernel code in memory. Can it?
0
votes
2answers
26 views

Can I increase the maximum number of scans in iwlist?

There are very many APs. In my opinion, there are at least 200 APs in this field. Scanning with iwlist will only scan up to 128 scans. The debug information of wpa_supplicant is limited to a maximum ...
0
votes
1answer
19 views

Atomic Fedora failed to parse kernel config

i try to setup kubernetes cluster on atomic fedora. I tried atomic fedora 27, 28 and 29 but I am facing same error on every release. Running kubeadm init ends with following error: failed to parse ...
0
votes
1answer
59 views

Is there a way to prevent root user from modifing kernel and boot loader?

Suppose that a regular linux machine is compromised by an attacker who obtained a root shell, he can modify the system kernel or modify boot loader to load another kernel. Is there a way to prevent ...
0
votes
1answer
45 views

Linux + how to know which CPU Cores was active last day

recently , we upgrade our redhat server ( version 7 ) from 4 CPU CORE to 32 CPU CORE is it possible to know which CPU was triggered during last day ? I mean how to know if the additional CPU that we ...
-2
votes
0answers
20 views

Syscall hijacking from kernel [migrated]

I want to intercept the open() syscall, for testing each time a file is opened by the user, the message “OPEN IS!” should be displayed in dmesg. The syscall table and open-call addresses in dmesg are ...
-1
votes
0answers
31 views

Mouse position in Linux kernel [migrated]

How I can get current mouse position (in coordinates {x,y}) in kernel space? I use the following code, but it returns me x and y positions as 255. Here is code: #include <linux/module.h> #...
0
votes
1answer
53 views

Using udisksctl to power off external hard drive causes hard lock

I possess an external USB 3.0 hard drive which is connected to my notebook. Of course, I do not want to just tug the connector off when I'm done; rather, I want it to safely spin down as per good ...
-1
votes
0answers
21 views

what does it mean - native PCIe service?

according to web link, we can see: https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html pcie_ports= [PCIE] PCIe ports handling: auto Ask the BIOS whether or not to use ...
0
votes
1answer
74 views

objdump : file format not recognized

I'm encountering these errors when trying to compile a new kernel under Gentoo... scripts/kconfig/conf --syncconfig Kconfig DESCEND objtool CC kernel/bounds.s CC arch/x86/kernel/asm-...
2
votes
0answers
28 views

Be informed when a specific vdso is run [migrated]

I'm currently trying to implement my own VDSO. I have used this tutorial which explains how to do this for a 2.6 kernel. I tested it and I got this working. (I succeeded in creating a kernel variable ...
3
votes
0answers
34 views

USB bulk write works in VM linux (on win7) but not in native linux (ubuntu 4.19)?

I'm experiencing weird behavior on a custom board that is flashed through USB hub and I'm trying to determine the root cause. When flashing is attempted from natively (Linux XPS-15-9560 4.19.0-041900-...
0
votes
0answers
14 views

Can no_console_suspend be set in runtime?

Is it possible to change this value in runtime without rebooting? I don't always have this problem, when I suspend right now I'm getting a failure and Suspending console(s) (use no_console_suspend ...
1
vote
0answers
18 views

Does every syscall require at most 1 capability on Linux?

I am trying to understand the relationship between capabilities and syscalls on Linux. As far as I know, the capabilities of a process are only ever considered when that process calls a syscall. When ...
1
vote
1answer
37 views

create a vdso in linux [closed]

I'm currently trying to implement my own VDSO. I have seen this tutorial which explains how to do this. However, this tutorial is made for Linux 2.6.x and I would like to use it on Linux 4.8.x. But ...
1
vote
1answer
65 views

USB-C to DisplayPort Adaper still not recognised in Linux kernel 4.19

I use Ubuntu 18.04 and upgraded to Linux kernel mainline 4.19.2 with ukuu, which purportedly supports DisplayPort alternate mode for USB-C. alex@gta-65:~$ uname -a Linux gta-65 4.19.2-041902-generic #...
1
vote
1answer
24 views

Can you edit address values in “/proc/$pid/mem” to reflect changes in that process?

I would like to see if I can edit a value in my program while it is running by directly changing the memory. My thought process (untested) is to do the following: Run the program. Open up "System ...
0
votes
0answers
12 views

I want to avoid 'clear_page' calls for system processes

So, I have a tightly controlled, heavy graphics system running on a custom build of android for a client. I want to avoid calls to 'clear_page()' in the memory manager so there will be more cpu for ...
0
votes
0answers
11 views

maintain a permanent keyring for a user across reboots

I want to hold credentials for a particular user in the kernel keyring. These credentials must be available across reboots. I was trying to do the following: keyctl add user keyname payload @u <...
1
vote
1answer
17 views

kernel 4.19: replacement for dentry_update_name_case()?

In 4.19 the dentry_update_name_case function was removed. What's the replacement for this?
9
votes
2answers
3k views

What does it take to run 64-bit userland software on a 32-bit kernel?

On Linux and Windows, I'm used to the situation that I require a 64-bit kernel to have a system with multiarch/WoW where I can run 32-bit and 64-bit software side-by-side. And then, years ago it blew ...
0
votes
0answers
13 views

Changing qdisc algorithm sysctl and tc

What qdisc is controlled via the tc command versus sysctl net.core.default_qdisc? Consider $ tc qdisc show dev eth2 qdisc mq 0: dev eth2 root $ sysctl net.core.default_qdisc net.core.default_qdisc ...
1
vote
0answers
41 views

Howto see messages that are subject to net_ratelimit?

OS: Ubuntu 14.04.3 Kernel: 3.13.0 I am running Linux Virtual Server (with keepalived) on that server. All ok. As of today, there is more network traffic on the LVS, and at the same time I start ...
0
votes
1answer
14 views

task_vector vs task_struct concept

I am having diffulty understanding how number of processes are limited by the size of task_vector I am reading this page, https://www.tldp.org/LDP/tlk/kernel/processes.html each process is ...
0
votes
1answer
28 views

Android kernel compiling error

When compiling the kernel, if I choose Ethernet Gadget (with CDC Ethernet support) or Network Control Model (NCM) instead of the Android composite device, I get an error: drivers/built-in.o:coresight-...
0
votes
0answers
7 views

nofiles parameter in limits.conf is not reflecting in the process running under the user

nofiles parameter in limits.conf is not reflecting in the process running under the user Following is the ulimit output ulimit -a core file size (blocks, -c) 0 data seg size (...
1
vote
0answers
47 views

2 LAN cables connected, 1 PCI bus and vice versa

When booting my pc with 2 LAN cables connected only one interface is registered. 03:00.0 and 04:00.0 $ dmesg | grep -P '0(3|4):00.0' [ 0.180140] pci 0000:04:00.0: [11ab:4362] type 00 class ...
0
votes
1answer
33 views

Evdev Wheel Emulation by keyboard

I love XInput mouse wheel emulation! Evdev Wheel Emulation can enable on any mouse button by running bellow command (9 is the mouse button that trigger Evdev Wheel Emulation) xinput set-prop $...
0
votes
1answer
18 views

Meaning of max segments queue param linux

What is meaning of value stored in /sys/block/sda/queue/max_segments (what are those segments?) ? Is it fixed value assigned to block device? Or can I change it in runtime? Where in kernel this value ...
0
votes
0answers
33 views

Unknown symbol device_destroy (err -22)

I'm trying to create a kernel module called Moduleprobe. I'm using gcc version 4.9.2 (GCC) The Code used works in the kernel version 3.12. I updated the kernel to the version 4.1. When calling ...
0
votes
1answer
39 views

Emulating a character device from userspace

We are currently working on building a system for data visualisation for different sensors. To make development of the Linux application possible we would need to emulate the behaviour of the ...
1
vote
0answers
15 views

Activation /Config of Preempt RT [duplicate]

I installed the Preempt RT patch, how can I know if it was installed correctly, and if it was activated? If it was right, what configuration shall be done, and how to do it?
0
votes
1answer
35 views

I have a dedicated with 2 SSDs, how to I group them to behave as 1?

I have a dedicated server which I will use to build virtual machines on top of using KVM (thank you, Virtualizor), the problem is, I do not physical access to the machine as it is rented from a big ...
0
votes
0answers
33 views

Atomic section in Linux user space

I need to take a timestamp of the Linux host clock and immediately raise an interrupt on a peripheral device via memory mapped access to its registers. It is crucial, that there is as little jitter ...
0
votes
1answer
129 views

Why can the kernel not use SSE/AVX registers and instructions?

This post from StackOverflow has this, In some environments there there is a restriction on certain instructions or using certain registers. For example, in the Linux kernel, use of SSE/AVX or FP ...
0
votes
1answer
44 views

Why won't make let me build my kernel from source?

$ make menuconfig Makefile:128: *** main directory cannot contain spaces nor colons. Stop. I get this error message. Why?
2
votes
0answers
69 views

Overheating while running Linux in Laptop

I've been running into issues while running Linux Mint MATE 19 64-bit in my laptop (Toshiba L750). It's installed in a SSD drive and there are 16GB of RAM installed. I purchased a SSD to move to ...
0
votes
1answer
96 views

Bind/Unbind Linux Module Automatically

I'm currently trying to create my own USB HID mouse driver as an override of the standard generic USB, which always gets in the way. How can I unbind the generic driver and rebind it to my specific ...