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Asked: 2024-09-23T18:52:19+05:30 In:

How can I initiate an SSH connection to machine A through machine B in a single command?

I have a bit of a situation here, and I could really use some help with it. So, I’ve been working on some projects that require me to access machine A. The catch is, I can only directly connect to machine B, which then has access to machine A. I know there’s a way to tunnel through using SSH, but I can’t quite seem to get it right.

I’ve heard of folks using the `ssh` command with some fancy flags or something like that, but my attempts have left me scratching my head. I really want to make this process smoother and faster, instead of hopping onto B first and then connecting to A. I’m all about efficiency, you know?

Here’s the scenario: machine A is sitting on a private network, and machine B is my only gateway. Machine B’s address is something like `192.168.1.2`, and machine A’s address is `192.168.1.100`. Ideally, I would like to initiate that SSH session to machine A directly through machine B without entering anything extra or needing to open multiple terminal windows.

I’ve seen some talk about using the `-J` option in SSH or maybe something with control paths—those sound like they could work, but I’m not sure how to piece it all together. Bonus points if you can explain it in a way that doesn’t assume I’m a networking wizard because I’m certainly not!

I guess what I’m really looking for is a single command that I can run that will connect me to machine A through machine B seamlessly. If you can share an example command and maybe break down what each part does, I’d appreciate it. I’m eager to cut down on the back-and-forth in my workflow. Anyone out there who can help a fellow techie out? Thanks in advance!

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    2 Answers


    1. Looks like you’re trying to connect to machine A through machine B without the extra hassle, and that’s totally possible with SSH! You’re right about the `-J` (jump host) option, and it makes things super easy. Here’s how you can do it:

      You can use the following command:

      ssh -J your_username@192.168.1.2 your_username@192.168.1.100

      Let’s break that down:

      • ssh: This is the command to start the SSH client.
      • -J: This option tells SSH that you want to use a jump host, which in your case is machine B.
      • your_username@192.168.1.2: Replace your_username with your actual username on machine B. This is how you log into machine B.
      • your_username@192.168.1.100: This is your target machine A, again replace your_username with your actual username on machine A.

      So, executing that command will connect you directly to machine A through machine B — no extra steps! Just make sure both machines accept SSH connections and that you have the right permissions on both.

      If you want to save some time in the future, you can also set up your SSH config file so you don’t have to type the full command each time. Just create or edit a file called ~/.ssh/config and add the following:

      Host machineA
    Hostname 192.168.1.100
    User your_username
    ProxyJump your_username@192.168.1.2

      Then you can just run:

      ssh machineA

      That’s it! You’re good to go with a more streamlined connection to machine A through B. Hope that simplifies things for you!



    2. To access machine A through machine B using SSH, you can use the `-J` option, which is specifically designed for this purpose. The command you would run looks like this: ssh -J userB@192.168.1.2 userA@192.168.1.100. Here’s the breakdown: ssh is the command to initiate an SSH session. The -J option allows you to specify the jump host (machine B), which is userB@192.168.1.2, where userB is your username on machine B. Finally, userA@192.168.1.100 is your destination user and machineA’s address on the private network.

      This single command streamlines your workflow by allowing you to connect directly to machine A without the need for multiple terminal sessions. Just ensure that you have SSH access set up correctly on both machines and that your keys, if used, have the proper permissions to connect seamlessly. If you prefer, you can also create an SSH config file (typically located at ~/.ssh/config) where you can set up a section for machine A that includes the jump host, making it even easier to connect with just a simple ssh userA command in the future.


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