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$ sudo apt-get install openssh-server
$ sudo service sshd status
//可以看到ssh的服务起来了

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//IPAddress hostname
192.168.1.111 jiemy
192.168.1.109 dengyg

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$ ping jiemy
<--output-->
PING jiemy (192.168.1.111) 56(84) bytes of data.

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//在每台机器上生成自己的自己的ssh公钥
$ ssh-keygen   //一路回车确认即可
//在每台机器上将*自己的公钥文件*重命名成自己的名字（例如jr.pub）放到共享文件夹
$ sudo cp ./.ssh/id_rsa.pub /mnt/jr.pub
//每台机器都完成后可以看到
$ ls /mnt/
dyg.pub  jiemy.pub  jr.pub Zx.pub
//在*某台机器*上将所有的公钥集合到authorized_keys中去
$ cd /mnt/
$ cat jr.pub jiemy.pub Zx.pub dyg.pub >> authorized_keys
//然后将authorized_keys放到*每个机器*的.ssh文件夹下
$ sudo cp authorized_keys ~/.ssh/

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//格式如下
Host hostname
    user name
//给个例子
Host jiemy
    user jiemy

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--------------------------------------------------------------------------
mpiexec was unable to launch the specified application as it could not access
or execute an executable:

Executable: /home/xuan/a.out
Node: jiemy

while attempting to start process rank 2.

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$ mkdir /mnt/test
$ cd /mnt/test
$ sudo gedit hello_c.c

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#include<mpi.h>
#include<stdio.h>
#include<string.h>
#include <unistd.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

void get(char *hname){
    struct hostent *hent;
    gethostname(hname, 128);
    
    hent = gethostbyname(hname);
    
}

int main(int argc,char *argv[])
{
    int my_rank;
    int p; 
    int source;
    int dest;
    int tag=0;
    char message[100];
    MPI_Status status;

    
    
    MPI_Init(&argc,&argv);
    
    MPI_Comm_rank(MPI_COMM_WORLD,&my_rank);
    
    MPI_Comm_size(MPI_COMM_WORLD,&p);

    if(my_rank!=0)
    {
        
        char hostname[128];
        get(hostname);
        sprintf(message,"Greeting from process %d,and ip is %s!",my_rank,hostname);
        dest=0;
        
        MPI_Send(message,strlen(message)+1,MPI_CHAR,dest,tag,MPI_COMM_WORLD);
    }else{
        for(source=1;source<p;source++){
            MPI_Recv(message,100,MPI_CHAR,source,tag,MPI_COMM_WORLD,&status);
            printf("%s\n",message);
        }
        char hostname[128];
        get(hostname);
        printf("Greeting from process %d,and ip is %s!\n",my_rank,hostname);
    }
    
    MPI_Finalize();
}

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# hostname slots=4
localhost slots=2
jiemy slots=2

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$ mpicc hello.c
$ mpiexec -hostfile hosts -np 4 ./a.out
<--output-->
Greeting from process 1,and ip is xuan-PC!
Greeting from process 2,and ip is jiemy-virtual-machine!
Greeting from process 3,and ip is jiemy-virtual-machine!
Greeting from process 0,and ip is xuan-PC!