# Kết nối ssh

Kết nối này cho phép truyền thông tin giữa hai máy tính kết nối mạng.

Ví dụ máy nguyenL520 kết nối với odroid. Cần chạy chương trình trên odroid mà cho phép xuất hiện cửa số trên màn hình cùa L520. Việc này quan trọng cho các ứng dụng, ví dụ chạy gedit để edit file hay chạy cutecom.

Câu lệnh:

ssh odroid\@odroid -Y

Nếu không có -Y thì chỉ là terminal bình thường, không cho phép hiển thị graphic

### De ket noi ssh khong can nhap di nhap lai password

## SSH login without password

### Your aim

You want to use Linux and OpenSSH to automate your tasks. Therefore you need an**automatic**login from host A / user a to Host B / user b. You don't want to enter any passwords, because you want to callsshfrom a within a shell script.

### How to do it

First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

```
a@A:~
>
 ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa): 
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A
```

Now usesshto create a directory\~/.sshas user b on B. (The directory may already exist, which is fine):

```
a@A:~
>
 ssh b@B mkdir -p .ssh
b@B's password:
```

Finally append a's new public key tob\@B:.ssh/authorized\_keysand enter b's password one last time:

```
a@A:~
>
 cat .ssh/id_rsa.pub | ssh b@B 'cat 
>
>
 .ssh/authorized_keys'
b@B's password:
```

From now on you can log into B as b from A as a without password:

```
a@A:~
>
 ssh b@B
```

**A note**from one of our readers: Depending on your version of SSH you might also have to do the following changes:

* Put the public key in

  .ssh/authorized\_keys2
* Change the permissions of

  .ssh

  to

  700
* Change the permissions of

  .ssh/authorized\_keys2

  to

  640

## Ket noi SSH ko can password, trong truong hop theo huong dan tren nhung ko thuc hien duoc

cho local ubuntu 16.04 (lhnguyen\@nguyenP51U16), de ket noi vao remote odroid 14.04 (odroid\@odroid)

Dua chu yeu vao noi dung bai bao sau:

> <https://www.thegeekstuff.com/2008/11/3-steps-to-perform-ssh-login-without-password-using-ssh-keygen-ssh-copy-id/>

#### Buoc 1:

> lhnguyen\@nguyenP51U16:\~$
>
> lhnguyen\@nguyenP51U16:\~$ ssh-keygen
>
> Se xuat hien kieu nhu sau
>
> Generating public/private rsa key pair.
>
> Enter file in which to save the key (/home/lhnguyen/.ssh/id\_rsa):
>
> /home/lhnguyen/.ssh/id\_rsa already exists.
>
> Overwrite (y/n)? y
>
> Enter passphrase (empty for no passphrase):
>
> Enter same passphrase again:
>
> Your identification has been saved in /home/lhnguyen/.ssh/id\_rsa.
>
> Your public key has been saved in /home/lhnguyen/.ssh/id\_rsa.pub.
>
> The key fingerprint is:
>
> SHA256:ol9DqiSagXYjNpXkuzhxtusaTq1mZHwFIrsdqng2L2w lhnguyen\@nguyenP51U16
>
> The key's randomart image is:
>
> +---\[RSA 2048]----+
>
> \| |
>
> |.. . |
>
> |..... |
>
> |. + .. |
>
> |.+ =. . S |
>
> |+=++.. + |
>
> |BO\*=+ . o |
>
> |BBE+oo . . |
>
> |=O+B+ . |
>
> +----\[SHA256]-----+

#### Buoc 2: Copy

> lhnguyen\@nguyenP51U16:\~$ ssh-copy-id -i \~/.ssh/id\_rsa.pub odroid\@odroid

#### Buoc 3: Thu ket noi, co the se van phai nhap password

> lhnguyen\@nguyenP51U16:\~$ ssh odroid\@odroid -Y
>
> sign\_and\_send\_pubkey: signing failed: agent refused operation
>
> odroid\@odroid's password:

#### Buoc 4: Chay ssh-add

> lhnguyen\@nguyenP51U16:\~$ ssh-add
>
> Identity added: /home/lhnguyen/.ssh/id\_rsa (/home/lhnguyen/.ssh/id\_rsa)

**Neu can co the list cac key co tren local**

> lhnguyen\@nguyenP51U16:\~$ ssh-add -l
>
> 2048 SHA256:ol9DqiSagXYjNpXkuzhxtusaTq1mZHwFIrsdqng2L2w /home/lhnguyen/.ssh/id\_rsa (RSA)
>
> 2048 SHA256:ol9DqiSagXYjNpXkuzhxtusaTq1mZHwFIrsdqng2L2w lhnguyen\@nguyenP51U16 (RSA)

#### Buoc 5: Ket noi lai

> lhnguyen\@nguyenP51U16:\~$ ssh odroid\@odroid -Y


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