Rendered at 06:59:10 GMT+0000 (Coordinated Universal Time) with Cloudflare Workers.
tangotaylor 15 hours ago [-]
My favorite use of this is peer-to-peer transfer of Docker images. The Docker CLI only allows you to use registries authenticated with HTTPS but there's an exception where it allows HTTP transfers over localhost.
So, if you use SSH tunneling to forward a port from localhost to a remote, then Docker unwittingly pushes to a remote. This is super useful "off the grid" with robotics/embedded applications where you don't want to bother with a registry and a good Internet connection.
This is really useful as you don't have to add an entry under insecure-registries for local registries that don't have valid certificates.
bitlad 13 hours ago [-]
You might as well handover the images to hackers.
QGQBGdeZREunxLe 8 hours ago [-]
A tad hyperbolic for a LAN registry
mmh0000 13 hours ago [-]
That's not quite true, you just need to add the `insecure-registries`[1] option with a list of either IP (or ip ranges) or hostnames that you want to allow without TLS.
Yes this is true. I should caveat that we distributed the tool among a team and we didn't want to ask them to all edit their daemon.json with an ever-expanding list of IP addresses.
fragmede 8 hours ago [-]
Could the tool you distributed update the daemon.json for your users so they don't have to change daemon.json manually?
Kampfschnitzel 14 hours ago [-]
iirc there's a setting to allow docker to trust and use http registries
i set it up a few years ago for my homelab
afiori 12 hours ago [-]
Which makes me think that I have never heard of signed images/artefacts
buredoranna 17 hours ago [-]
I'll mention it here, because I learned about it here.
"~C" will drop you into the SSH command line, allowing you to, among other things, effect port forwarding
-L8080:localhost:443
Learning that "~C" exists, and what you can do with it, has supercharged my use of SSH tunnels, which were already awesome on their own.
But for some reason this has been disabled by default in more recent ssh configurations... to ensure its available
-o EnableEscapeCommandline=yes
or, in your ~/.ssh/config
EnableEscapeCommandline yes
(edit: formatting)
telotortium 16 hours ago [-]
Important to note that `~` SSH commands work only right after you press Enter - it doesn’t trigger everywhere you press `~`.
Also EnableEscapeCommandline fortunately only affects `~C` - the all-important `~.` to kill a hung SSH session still works with it disabled.
ptaffs 15 hours ago [-]
so many time i have inadvertently ended a session with a fat fingered ~.
trentnelson 8 hours ago [-]
Not ssh related but I regularly suspend my terminal with Ctrl-S by accident, usually when going for Ctrl-C/V.
That was a nightmare to triage back in the late 90s when I did it. Thankfully Ctrl-Q (I think it’s Q) “resumes”, so, easy fix if you know what you’ve done.
coryrc 6 hours ago [-]
Correct.
- software flow control user
jojo2354 6 hours ago [-]
Eh, once I started using master sockets, I never went back. Problem with ~C is it's hard to keep track of what you have open.
It is surprising how many times I see this content (this version might be marked “Published: Jun 19, 2026” but I've definitely seen those exact diagrams before, starting at least a few years ago, and the same content around them in many tutorials before that) without it being updated to mention jump-hosts.
Support was added to OpenSSH about a decade ago? Even on a low moving Linux distro like Debian/LTS everyone should have support by now.
16 hours ago [-]
idatum 7 hours ago [-]
What I've found beautiful about -J is the host you jump through requires no privileges on the final host. Only my laptop has the SSH key to access my home server, not my cheap VPS.
And this allows me to have zero open ports on my home internet. I do a reverse tunnel to my VPS from my home server (in a FreeBSD jail), and that port is what my laptop client jumps through.
saltcured 12 hours ago [-]
For me, this is always used via ProxyJump rules in my ~/.ssh/config
It is also nice that it works recursively, so I can logically structure my rules so that the one for my regular targets say to use bastion1, then the rule for bastion1 says to go via bastion 2, etc.
I find this easier to reason about and maintain rather than juggling a bunch of these multi-step rules.
05 10 hours ago [-]
And with match/exec rules you can always connect to MyHost and make it conditional whether to use a jumphost or not, so it's like an on demand vpn.. only with ssh.
Match host="MyHost" exec "! grep Home ~/.wifi-loc-control/.current"
ProxyJump home-jumphost.mydomain.tld
Are you using SSH key auth or password authenticating three times when you do this?
chasil 12 hours ago [-]
If you don't have an agent running with an accessible key, then you will get three password prompts, with suggestions for any default keys.
The final target is a pre-elliptic curve OpenSSH server, so legacy is enabled. I could probably have removed that for clarity.
C:\Users\me\>ssh -J me@bhost1,me@bhost2 -o KexAlgorithms=diffie-hellman-group14-sha1 -o HostKeyAlgorithms=ssh-rsa -o MACs=hmac-sha1 oracle@target
Enter passphrase for key 'C:\Users\me/.ssh/id_ed25519':
me@host1's password:
Enter passphrase for key 'C:\Users\me/.ssh/id_ed25519':
me@host2's password:
oracle@target's password:
Last login: Wed Jun 24 13:29:55 2026 from bhost2
That client is Microsoft's port of OpenSSH.
saltcured 12 hours ago [-]
I always use keys in my SSH agent.
Because the jump mechanism works via use of TCP forwarding, each host authn step is talking "directly" to your client. Importantly, this means it still works without requiring "agent forwarding" for the connection you are making.
pss314 45 minutes ago [-]
Hak5 video that helped me understand many years ago about the practical usage of SSH forwarding
sshuttle is amazing. I've used it extensively on stupidly configured networks, super useful tool.
hylaride 17 hours ago [-]
Learning how SSH port forwarding is great as a pseudo-vpn for everything from GUI-client database access to (in physical infra) access to web-admin tools for appliances.
The socks proxy support can also deal with bad web filtering and privacy issues on public wifi networks (though nowadays if you're ssh'ing to a cloud IP, you'll get lots of "bot" restrictions).
saltcured 12 hours ago [-]
Yeah, I get use out of the SOCKS proxy mode in combination with a "split VPN" at work.
I need VPN to get into some internal resources via SSH, but there are lots of external/public/AWS resources I also need to access, and the full VPN adds too much overhead and fragility for those.
Using the available split VPN, I can point a browser instance at a localhost SOCKS proxy port to relay over SSH + VPN for other web resources I need to access internally.
Unfortunately, Firefox proxy config rules are sort of backwards for my needs. I want to say "only use proxy for these 3 domains" whereas it wants to use the proxy by default and only allow me to bypass specific domains.
hylaride 11 hours ago [-]
In the past, I've used plugins to do just what you ask. FoxyProxy Standard did the trick (it looks like there's now at least another more standard "VPN" version, too). It looks like Firefox does have support for Native PAC files that'll also do the trick: https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Pro...
TacticalCoder 10 hours ago [-]
> The socks proxy support ...
I just love SOCKS proxy in SSH tunnels: at some point I had a dedicated server (on a fixed IP) with countless machines (usually headless Pis dropped at a family member's place and/or SME office) automatically setting up, 24/7, reverse tunnels to that dedicated server.
Then I could, from anywhere, both access their LANs (to fix stuff) and have a browser, running locally, pretending to be in this or that country.
Basically because I had all those reverse tunnels always there, I could always decide how to use them (just SSH in or SOCKS in etc.).
bheadmaster 16 hours ago [-]
If you have many different remote devices behind NATs or firewalls, a cool trick to access them all via EC2 server (or such) is to setup Remote Forwarding via UNIX socket on the server side, to devices' port 22. Preferably, UNIX socket filenames should start with a common prefix, so an SSH config can be written that will use ssh+socat in a ProxyCommand to establish the connection.
It's amazing how lightweight this method actually is. I have managed to connect hundreds of devices using a single EC2 nano instance.
saltcured 12 hours ago [-]
I think the more modern ProxyJump rule is superior for this. Just let it manage the actual TCP forwarding for you automatically. It's just the normal "bastion host" concept.
Particularly, you can use name patterns to apply the same rule broadly, assuming you have some systematic naming scheme for your eventual target devices.
ranger_danger 14 hours ago [-]
Do you have more info on this method? How is the remote forwarding actually done?
It’s amazing what you can learn by reading the manual.
felooboolooomba 17 hours ago [-]
It is, because manuals are often not the best way to learn things. Most software manuals are reference manuals. SSH man page isn't too bad. I learned most of my SSH knowledge from it, but I'm not sure it's the best way to do it.
matltc 16 hours ago [-]
For me, the best way to learn a tool is for a quick example or two showing its utility, then practicing with those, reading the man as needed on specific flags. Google or bot ”how do x" ? Repeat : done
Some pages have a nice up-front synopsis of flags, others put them in a wall of text. Browsing the former can supplant Google, /\b-x while paging is helpful for the latter.
16 hours ago [-]
trollbridge 17 hours ago [-]
When I see one of these with obvious AI tells at the top (sentences lacking a subject or verb), I ask myself:
Can’t I just open up a harness and prompt “Teach me how to do X?”
lfx 17 hours ago [-]
I do this all the time, I have a skill/gem with instructions on how I want to receive info, how to format and so on. Really helps to go fast to get the point.
Oxodao 16 hours ago [-]
Could you share it? I'd be interested to get idea to make my own
lfx 15 hours ago [-]
It goes like this:
---
As an expert tutorial creator for experienced engineers, you take the input the user request and make interactive tutorial. Default style is technology, tech is mac and linux. Default style is 20mins, but you ask for the timeline. Also do not forget to provide the cost of technologies used.
---
GL26 17 hours ago [-]
I personally do this, ask claude code to teach me about concepts I don't know about when it codes something, and only then I accept what it suggests to me
segphault 17 hours ago [-]
Or you could just install something like Tailscale and never have to think about it again.
guluarte 5 hours ago [-]
or tell an llm to do it for you
riobard 17 hours ago [-]
There's a asymmetry here that "-R" works both for reverse static and dynamic (using SOCKS protocol) forwarding, but "-D" is required for dynamic forwarding which "-L" cannot do.
Why is that?
hylaride 16 hours ago [-]
It's historical. Some older flags could be easily extended for dynamic port support and others could not.
17 hours ago [-]
felooboolooomba 17 hours ago [-]
As a sysadmin, one of your biggest ROI is learning the ins and outs of SSH.
17 hours ago [-]
phbeks 12 hours ago [-]
Thanks! I will keep this for reference. I use ssh alot but thie reminds me that I can learn new ways of tunneling :-)
ktm5j 12 hours ago [-]
Weird.. I have almost this exact same "cheat sheet" printed out and stuck up on my whiteboard.. except it's slightly different. Only 4 panels instead of 6 and the panels don't have titles.
I know this is a solid "cool story bro" moment, but whatever hah
nekusar 10 hours ago [-]
BTW I use this and a systemd unit file and SSH tunnel my Jellyfin to a public VPS to its local host.
I then use nginx to proxy it.
Because its a unit file, sshd reconnects if my ISP's IP changes. Does so within 30s. Also hides my ISP IP in case I have to turn it off.
And no data is effectively on the VPS. Its just a mostly empty machine.
ggm 9 hours ago [-]
Always annoys me -p(port) for ssh clashes with -p(reserve permissions) for sftp and scp. Unavoidable given history.
Also annoys me we "invented" ssh:// url format after the tools were baked so it's a somewhat odd bonding into the model.
matltc 16 hours ago [-]
Very refreshing to see a utilitarian series such as this. Disappointing that the latest ai drama gets 20x more discussion and visibility on this site
ranger_danger 15 hours ago [-]
Another option that I never see mentioned anywhere is -w which allows you to create either layer2 or layer3 tunnels via a tun(4) interface.
Bender 16 hours ago [-]
Should add how to bypass MFA using phishing and SSH Multiplexing to the article.
So, if you use SSH tunneling to forward a port from localhost to a remote, then Docker unwittingly pushes to a remote. This is super useful "off the grid" with robotics/embedded applications where you don't want to bother with a registry and a good Internet connection.
Example, docker pussh: https://github.com/psviderski/unregistry
```/etc/docker/daemon.json
```[1] https://docs.docker.com/reference/cli/dockerd/#insecure-regi...
i set it up a few years ago for my homelab
"~C" will drop you into the SSH command line, allowing you to, among other things, effect port forwarding
Learning that "~C" exists, and what you can do with it, has supercharged my use of SSH tunnels, which were already awesome on their own.But for some reason this has been disabled by default in more recent ssh configurations... to ensure its available
or, in your ~/.ssh/config (edit: formatting)Also EnableEscapeCommandline fortunately only affects `~C` - the all-important `~.` to kill a hung SSH session still works with it disabled.
That was a nightmare to triage back in the late 90s when I did it. Thankfully Ctrl-Q (I think it’s Q) “resumes”, so, easy fix if you know what you’ve done.
- software flow control user
Goes over similar content as TFA, in perhaps a little more depth. Indispensable sysadmin knowledge.
https://www.openssh.org/releasenotes.html
Support was added to OpenSSH about a decade ago? Even on a low moving Linux distro like Debian/LTS everyone should have support by now.
And this allows me to have zero open ports on my home internet. I do a reverse tunnel to my VPS from my home server (in a FreeBSD jail), and that port is what my laptop client jumps through.
It is also nice that it works recursively, so I can logically structure my rules so that the one for my regular targets say to use bastion1, then the rule for bastion1 says to go via bastion 2, etc.
I find this easier to reason about and maintain rather than juggling a bunch of these multi-step rules.
Are you using SSH key auth or password authenticating three times when you do this?
The final target is a pre-elliptic curve OpenSSH server, so legacy is enabled. I could probably have removed that for clarity.
That client is Microsoft's port of OpenSSH.Because the jump mechanism works via use of TCP forwarding, each host authn step is talking "directly" to your client. Importantly, this means it still works without requiring "agent forwarding" for the connection you are making.
Hak5 - SSH Forwarding: Local vs Remote with examples, Hak5 1113 part1 https://www.youtube.com/watch?v=g_Row8zEJZc
[0] https://github.com/sshuttle/sshuttle
The socks proxy support can also deal with bad web filtering and privacy issues on public wifi networks (though nowadays if you're ssh'ing to a cloud IP, you'll get lots of "bot" restrictions).
I need VPN to get into some internal resources via SSH, but there are lots of external/public/AWS resources I also need to access, and the full VPN adds too much overhead and fragility for those.
Using the available split VPN, I can point a browser instance at a localhost SOCKS proxy port to relay over SSH + VPN for other web resources I need to access internally.
Unfortunately, Firefox proxy config rules are sort of backwards for my needs. I want to say "only use proxy for these 3 domains" whereas it wants to use the proxy by default and only allow me to bypass specific domains.
I just love SOCKS proxy in SSH tunnels: at some point I had a dedicated server (on a fixed IP) with countless machines (usually headless Pis dropped at a family member's place and/or SME office) automatically setting up, 24/7, reverse tunnels to that dedicated server.
Then I could, from anywhere, both access their LANs (to fix stuff) and have a browser, running locally, pretending to be in this or that country.
Basically because I had all those reverse tunnels always there, I could always decide how to use them (just SSH in or SOCKS in etc.).
It's amazing how lightweight this method actually is. I have managed to connect hundreds of devices using a single EC2 nano instance.
Particularly, you can use name patterns to apply the same rule broadly, assuming you have some systematic naming scheme for your eventual target devices.
Some pages have a nice up-front synopsis of flags, others put them in a wall of text. Browsing the former can supplant Google, /\b-x while paging is helpful for the latter.
Can’t I just open up a harness and prompt “Teach me how to do X?”
Why is that?
I know this is a solid "cool story bro" moment, but whatever hah
I then use nginx to proxy it.
Because its a unit file, sshd reconnects if my ISP's IP changes. Does so within 30s. Also hides my ISP IP in case I have to turn it off.
And no data is effectively on the VPS. Its just a mostly empty machine.
Also annoys me we "invented" ssh:// url format after the tools were baked so it's a somewhat odd bonding into the model.