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RHEL7系统管理之内核管理,文件打开方式点错之后

来源:http://www.nb-machinery.com 作者:网上十大正规赌博平台 时间:2019-10-28 21:02

星期日, 02. 九月 2018 11:58下午 - beautifulzzzz

  1. Kdump工具

自己动手改下注册表就行 文件打开关联被改了但是在这里面却不能选择系统默认的打开方式 改下注册表就能恢复默认了 开始--运行--regedit 打开注册表 找到键HKEY_CURRENT_USERSOFTWAREMICROSOFTWINDOWSCURRENTVERSIONEXPLORERFILEXTS找到你想恢复的那个文件的后缀删除它下面的UserChoice比如修改.jpg的打开方式 就找到.jpg.. 你是mdf文件的打开关联被修改了 就找到.mdf 删除它下面的UserChoice就行了.

图片 1

  Kdump的工作机制是在内核崩溃时, 通过kexec 工具由BIOS启动一个备用内核, 由备用内核执行一系列任务,保存内存中崩溃内核的状态, 供后续故障分析用.

转自

1. Introduction

Bluez is the default Bluetooth protocol stack on Linux. It should be present and installed on your Linux distribution. If not, building and installing from source is not too difficult:

  • Download the latest stable source release of Bluez from here. Unzip the compressed file you downloaded.
  • Install the headers and libraries required for Bluez compilation:

图片 2

  本文默认AMD或INTEL X86_64架构, RHEL7系统环境. 

2. Download And Install

I follow the blog (Installing Bluez 5.44 onto Raspbian?) to install bluez-5.50.

Download the most recent version from the official page:.

For example, at the time of writing it was 5.50, so I used(on my pi):

wget http://www.kernel.org/pub/linux/bluetooth/bluez-5.50.tar.xz

Then I extracted it and built it:

tar -xf bluez-5.50.tar.xz
cd bluez-5.50

Read the README! It lists the dependencies and the configure switches:

Install the dependencies first: (glib, dbus, libdbus, udev, etc.)

sudo apt install libdbus-1-dev libudev-dev libical-dev libreadline-dev

note: If you do not install the libdbus-1-dev, you will later get this strange error:

configure: error: D-Bus >= 1.6 is required

once you've installed dependencies, you can configure switches:

./configure --prefix=/usr --mandir=/usr/share/man --sysconfdir=/etc --localstatedir=/var  --enable-experimental

then do:

make
sudo make install

It takes maybe 10 minutes to compile. After installing, you should find bluetoothd in /usr/libexec/bluetooth. You should also see bluetoothd in /usr/lib/bluetooth.

Go to each of these directories and type

./bluetoothd --version

You'll note that the one in libexec is new and the one in lib is old.

In order to make sure that d-bus is talking to you new BlueZ 5.50 and not your old BlueZ 5.43, you need to tell systemd to use the new bluetooth daemon:

sudo vim /lib/systemd/system/bluetooth.service

Make sure the exec.start line points to your new daemon in /usr/libexec/bluetooth.

For me, that wasn't enough. No matter what, upon restart I always got bluetoothd 5.43... So I just created a symlink from the old one to the new.

First rename the old file:

sudo mv /usr/lib/bluetooth/bluetoothd /usr/lib/bluetooth/bluetoothd-543.orig

Create the symlink:

sudo ln -s /usr/libexec/bluetooth/bluetoothd /usr/lib/bluetooth/bluetoothd
sudo systemctl daemon-reload

That should do it.

图片 3

1.1 内核管理工具Kdump安装

3. How to use the bluez and hcitool

  Kdump是RHEL7中自带的内核管理工具.在RHEL7.1之前的版本,kdump作为安装完成之后的可选组件自动安装,从RHEL7.1开始kdump被植入安装界面,作为系统基础工具供安装选择.

3.1 setup bluetooth service

Start the bluetooth service and enable automatic startup, assuming you're using systemd as the init daemon:

sudo systemctl start bluetooth.service
sudo systemctl enable bluetooth.service

可以通过下面命令直接RPM包安装.

3.2 hcitool scan for bluetooth devices

Before start scanning make sure that your bluetooth device is turned on and not blocked, you can check that with the rfkill command:

sudo rfkill list

If the bluetooth device is blocked (soft or hard blocked), unblock it with the rfkill command again:

sudo rfkill unblock bluetooth

Bring up the bluetooth device with hciconfig command and start scanning, make sure the target device's bluetooth is on and It's discoverable:

sudo hciconfig hci0 up
hcitool scan

Wait few moment to complete the hcitool scan or hcitool lescan, the results will be something like bellow:

图片 4

图片 5

Here 00:1A:7D:DA:71:0A is the bluetooth MAC address and SHEN-PC is the name of the bluetooth device, i.e. an PC.

note: use hcitool lescan will forever scan ble devices, if use ctrl c stop it, it will show error(ref to LINKS 4 to solve):

hcitool lescan
Set scan parameters failed: Input/output error

yum -y install kexec-tools
rpm -q kexec-tools

3.3 bluetooth service discovery

Now we have the bluetooth MAC address of the target device, use the sdptool command to know which services (like DUN, Handsfree audio) are available on that target device.

sdptool browse 28:ED:6A:A0:26:B7

You can also use the interactive bluetoothctl tool for this purpose.

If the target device is present, you can ping it with l2ping command, requires root privilege:

➜  bluez-5.50  sudo l2ping 94:87:E0:B3:AC:6F
Ping: 94:87:E0:B3:AC:6F from B8:27:EB:8E:CC:51 (data size 44) ...
44 bytes from 94:87:E0:B3:AC:6F id 0 time 53.94ms
44 bytes from 94:87:E0:B3:AC:6F id 1 time 77.12ms
44 bytes from 94:87:E0:B3:AC:6F id 2 time 38.63ms
44 bytes from 94:87:E0:B3:AC:6F id 3 time 46.13ms
44 bytes from 94:87:E0:B3:AC:6F id 4 time 59.96ms
5 sent, 5 received, 0% loss

So, bluetooth service discovery is useful to determine the type of the device, like if it's a bluetooth mp3 player or it's a keyboard.

图片 6

同时,Kdump还配备了图形化管理工具,可以通过下面命令安装.

LINKS

  • 1.Bluetooth on Modern Linux by Szymon Janc
  • 2.dbus-python tutorial
  • 3.Linux bluetooth setup with bluez and hcitool
  • 4.hcitool lescan shows I/O error

图片 7

@beautifulzzzz
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yum -y install system-config-kdump

  对于RHEL7.4及之后的版本,kdump支持INTEL IOMMU. 而不支持RHEL7.3及之前的版本.

1.2 通过命令行配置kdump内存容量

  kdump能监控系统内核运行状态,其地位比较特殊. kdump的内存空间是在系统启动时,由引导程序分配的,相对于系统内核,kdump内存是一个独立的空间.

可以通过如下命令指定kdump的内存空间大小.

crashkernel=128M     #为kdump保留128M的内存空间.

   crashkernel的值可以设置成“auto",在一些拥有较大内存的系统中,利于实现Kdump的自动化管理.

crashkernel=auto

  当然,crashkernel的值还可以通过如下形式实现更灵活的配置.

  crashkernel=<范围1>:<大小1>, <范围2>:<大小2>

crashkernel=512M-2G:64M,2G-:128M    #当系统内存在512M-2G之间时,为Kdump保留64M的内存空间;当系统内存大于2G时,为Kdump保留128M的内存空间.

  还可以这样:

crashkernel=128M@16M    #为Kdump保留128M的内存空间,内存地址从16M(physical address 0x01000000)开始.

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