Hack vui,gửi tin nhắn đến tất cả user cùng login vào trong hệ thống Linux (Show on Terminal)

- Dùng lệnh : wall

# wall "System will go down for 2 hours maintenance at 13:00 PM"

Kết quả:

Broadcast message from root@coge (pts/2) (Sat Dec  9 13:27:24 2017):

- Bạn cũng có thể check có bao nhiêu user đang login vào trong system bằng lệnh:
# who

Cách git clone từ ssh | git clone ssh://git@github.com//.git

Để git source code thông qua ssh:

git clone ssh://git@github.com/<user>/<repository name>.git

Nếu lỗi xảy ra:

fatal: destination path 'ssh://user@server:/GitRepos/myproject.git' already exists and is not an empty directory.

Fix:

For setting up git to clone via ssh see:

• Generating SSH Keys and add your generated key in Account Settings -> SSH Keys
• Cloning with SSH

1. Kiểm tra xem git đã có ssh key chưa:

$ ls -al ~/.ssh

# Lists the files in your .ssh directory, if they exist

Nếu có thì nó sẽ có file .pub như sau:

• id_rsa.pub
• id_ecdsa.pub
• id_ed25519.pub

2. Nếu chưa có ssh key thì phải add

$ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

email: là email bạn đăng ký git

Tiếp:

Enter a file in which to save the key (/c/Users/you/.ssh/id_rsa):[Press enter]

Thêm mật khẩu:

Enter passphrase (empty for no passphrase): [Type a passphrase]
> Enter same passphrase again: [Type passphrase again]

3. Add ssh-key vào ssh-agent

$ eval $(ssh-agent -s)

$ ssh-add ~/.ssh/id_rsa

DAC with STM32 | Study STM32 with Standard Peripheral Library

@par Example Description 

This example provides a short description of how to use the DAC peripheral to
generate several signals using DMA controller.
When the user presses the KEY push-button, DMA transfers the two selected
waveforms to the DAC.
For each press on KEY button, 2 signals has been selected and can be monitored on 
the two DAC channels:
    - Escalator waveform (Channel 1) and Sine waveForm (Channel 2).
    - Noise waveform (Channel 1) and Triangle waveform (Channel 2).


@par Directory contents 

  - DAC/DAC_SignalsGeneration/stm32f4xx_conf.h    Library Configuration file
  - DAC/DAC_SignalsGeneration/stm32f4xx_it.c      Interrupt handlers
  - DAC/DAC_SignalsGeneration/stm32f4xx_it.h      Interrupt handlers header file
  - DAC/DAC_SignalsGeneration/main.c              Main program
  - DAC/DAC_SignalsGeneration/main.h              Main program header file
  - DAC/DAC_SignalsGeneration/system_stm32f4xx.c  STM32F4xx system source file


1. main.c
/* Includes ------------------------------------------------------------------*/
#include "main.h"


DAC_InitTypeDef  DAC_InitStructure;

const uint16_t aSine12bit[32] = {
                      2047, 2447, 2831, 3185, 3498, 3750, 3939, 4056, 4095, 4056,
                      3939, 3750, 3495, 3185, 2831, 2447, 2047, 1647, 1263, 909,
                      599, 344, 155, 38, 0, 38, 155, 344, 599, 909, 1263, 1647};
const uint8_t aEscalator8bit[6] = {0x0, 0x33, 0x66, 0x99, 0xCC, 0xFF};

__IO uint8_t ubSelectedWavesForm = 1;
__IO uint8_t ubKeyPressed = SET;

/* Private function prototypes -----------------------------------------------*/
static void TIM6_Config(void);

static void DAC_Ch1_EscalatorConfig(void);
static void DAC_Ch2_SineWaveConfig(void);

static void DAC_Ch1_NoiseConfig(void);
static void DAC_Ch2_TriangleConfig(void);


int main(void)
{
  /*!< At this stage the microcontroller clock setting is already configured,
       this is done through SystemInit() function which is called from startup
       files (startup_stm32f40xx.s/startup_stm32f427x.s) before to branch to
       application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f4xx.c file
     */   

  /* Preconfiguration before using DAC----------------------------------------*/
  GPIO_InitTypeDef GPIO_InitStructure;

  /* DMA1 clock enable */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);
  /* GPIOA clock enable (to be used with DAC) */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);                       
  /* DAC Periph clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);

  /* DAC channel 1 & 2 (DAC_OUT1 = PA.4)(DAC_OUT2 = PA.5) configuration */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* TIM6 Configuration ------------------------------------------------------*/
  TIM6_Config(); 
 
  /* Configures Key Button */
  STM_EVAL_PBInit(BUTTON_KEY, BUTTON_MODE_EXTI);
 
  while (1)
  {
    /* If the Key is pressed */
    if (ubKeyPressed != RESET)
    {           
      DAC_DeInit();

      /* select waves forms according to the Key Button status */
      if (ubSelectedWavesForm == 1)
      {
        /* The sine wave and the escalator wave has been selected */

        /* Escalator Wave generator ------------------------------------------*/
        DAC_Ch1_EscalatorConfig();

        /* Sine Wave generator -----------------------------------------------*/
        DAC_Ch2_SineWaveConfig();
       
      }
      else
      {
        /* The triangle wave and the noise wave has been selected */

        /* Noise Wave generator ----------------------------------------------*/
        DAC_Ch1_NoiseConfig();

        /* Triangle Wave generator -------------------------------------------*/
        DAC_Ch2_TriangleConfig();
      }
     
      ubKeyPressed = RESET;
    }
  }
}

/**           
  * @brief  TIM6 Configuration
  * @note   TIM6 configuration is based on APB1 frequency
  * @note   TIM6 Update event occurs each TIM6CLK/256 
  * @param  None
  * @retval None
  */
static void TIM6_Config(void)
{
  TIM_TimeBaseInitTypeDef    TIM_TimeBaseStructure;
  /* TIM6 Periph clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6, ENABLE);
 
  /* --------------------------------------------------------
  TIM3 input clock (TIM6CLK) is set to 2 * APB1 clock (PCLK1),
  since APB1 prescaler is different from 1. 
    TIM6CLK = 2 * PCLK1 
    TIM6CLK = HCLK / 2 = SystemCoreClock /2
         
  TIM6 Update event occurs each TIM6CLK/256

  Note:
   SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f4xx.c file.
   Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()
   function to update SystemCoreClock variable value. Otherwise, any configuration
   based on this variable will be incorrect.   

  ----------------------------------------------------------- */
  /* Time base configuration */
  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
  TIM_TimeBaseStructure.TIM_Period = 0xFF;         
  TIM_TimeBaseStructure.TIM_Prescaler = 0;     
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;   
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 
  TIM_TimeBaseInit(TIM6, &TIM_TimeBaseStructure);

  /* TIM6 TRGO selection */
  TIM_SelectOutputTrigger(TIM6, TIM_TRGOSource_Update);
 
  /* TIM6 enable counter */
  TIM_Cmd(TIM6, ENABLE);
}

/**
  * @brief  DAC  Channel2 SineWave Configuration
  * @param  None
  * @retval None
  */
static void DAC_Ch2_SineWaveConfig(void)
{
  DMA_InitTypeDef DMA_InitStructure;
 
  /* DAC channel2 Configuration */
  DAC_InitStructure.DAC_Trigger = DAC_Trigger_T6_TRGO;
  DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
  DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
  DAC_Init(DAC_Channel_2, &DAC_InitStructure);

  /* DMA1_Stream6 channel7 configuration **************************************/
  DMA_DeInit(DMA1_Stream6);
  DMA_InitStructure.DMA_Channel = DMA_Channel_7; 
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)DAC_DHR12R2_ADDRESS;
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&aSine12bit;
  DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
  DMA_InitStructure.DMA_BufferSize = 32;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;       
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(DMA1_Stream6, &DMA_InitStructure);

  /* Enable DMA1_Stream6 */
  DMA_Cmd(DMA1_Stream6, ENABLE);

  /* Enable DAC Channel2 */
  DAC_Cmd(DAC_Channel_2, ENABLE);

  /* Enable DMA for DAC Channel2 */
  DAC_DMACmd(DAC_Channel_2, ENABLE);
}

/**
  * @brief  DAC Channel1 Escalator Configuration
  * @param  None
  * @retval None
  */
static void DAC_Ch1_EscalatorConfig(void)
{
  DMA_InitTypeDef DMA_InitStructure;

  /* DAC channel1 Configuration */
  DAC_InitStructure.DAC_Trigger = DAC_Trigger_T6_TRGO;
  DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
  DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
  DAC_Init(DAC_Channel_1, &DAC_InitStructure);

  /* DMA1_Stream5 channel7 configuration **************************************/ 
  DMA_DeInit(DMA1_Stream5);
  DMA_InitStructure.DMA_Channel = DMA_Channel_7; 
  DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR8R1_ADDRESS;
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&aEscalator8bit;
  DMA_InitStructure.DMA_BufferSize = 6;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
  DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;       
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(DMA1_Stream5, &DMA_InitStructure);   

  /* Enable DMA1_Stream5 */
  DMA_Cmd(DMA1_Stream5, ENABLE);
 
  /* Enable DAC Channel1 */
  DAC_Cmd(DAC_Channel_1, ENABLE);

  /* Enable DMA for DAC Channel1 */
  DAC_DMACmd(DAC_Channel_1, ENABLE);
}

/**
  * @brief  DAC Channel2 Triangle Configuration
  * @param  None
  * @retval None
  */
static void DAC_Ch2_TriangleConfig(void)
{
 /* DAC channel2 Configuration */
  DAC_InitStructure.DAC_Trigger = DAC_Trigger_T6_TRGO;
  DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_Triangle;
  DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_TriangleAmplitude_1023;
  DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
  DAC_Init(DAC_Channel_2, &DAC_InitStructure);

  /* Enable DAC Channel2 */
  DAC_Cmd(DAC_Channel_2, ENABLE);

  /* Set DAC channel2 DHR12RD register */
  DAC_SetChannel2Data(DAC_Align_12b_R, 0x100);
}

/**
  * @brief  DAC  Channel1 Noise Configuration
  * @param  None
  * @retval None
  */
static void DAC_Ch1_NoiseConfig(void)
{
 /* DAC channel1 Configuration */
  DAC_InitStructure.DAC_Trigger = DAC_Trigger_T6_TRGO;
  DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_Noise;
  DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_LFSRUnmask_Bits10_0;
  DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
  DAC_Init(DAC_Channel_1, &DAC_InitStructure);

  /* Enable DAC Channel1 */
  DAC_Cmd(DAC_Channel_1, ENABLE);

  /* Set DAC Channel1 DHR12L register */
  DAC_SetChannel1Data(DAC_Align_12b_L, 0x7FF0);
}

#ifdef  USE_FULL_ASSERT

/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t* file, uint32_t line)
{
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

  /* Infinite loop */
  while (1)
  {
  }
}

#endif

Nén và giải nén trong linux: zip, tar.gz và tar.bz2

Trong hệ thống *nix tồn tại một số dạng nén cơ bản như: zip, tar.gz và tar.bz2. Dưới đây là một vài ví dụ về cách nén và giải nén với những định dạng đó.

1. Nén và giải nén file có đuôi .gz

1.1 Nén
#gzip [tên file]

1.2 Giải nén
#gunzip [tên file]

2. Gom và bung tập tin hoặc thư mục đuôi .tar

2.1 Gom
#tar -cvf [tênfile.tar] [file1] [file2] …

2.2 Bung
#tar -xvf [file.tar]

2.3 Nén và Gom
#tar -zcvf [file.tar.gz] file1 file2 …

2.4 Giải nén và bung
#tar -zxvf [file.tar.gz]

3. Giải nén file có đuôi .bz2
#tar xjvf [file.tar.bz2]

Các định dạng khác :

1. ZIP

1.1 Nén một thư mục, sử dụng:
# zip -r folder.zip folder
1.2 Giải nén, sử dụng:
# unzip file.zip

2. TAR.GZ

2.1 Nén một thư mục dạng .gz, sử dụng:
# tar -zcf folder.tar.gz folder
2.2 Giải nén, sử dụng:
# tar -zxvf file.tar.gz

3. TAR.BZ2

3.1 Nén một thư mục dạng .bz2, sử dụng:
$ tar -jcf folder.tar.bz2 folder
3.2 Giải nén, sử dụng:
$ tar -jxvf file.tar.bz2
-Để biết thêm cách sử dụng lệnh man.