Also, authorizing by key but restricting the (passwordless) key to certain commands, allowing for remote action automation. [0]Ssh agent forwarding is also particularly awesome instead of naively scattering keys.
Ssh ControlMaster allowing to reuse connections can really improve responsiveness. Tip: start the master connection as a daemon (-f), so as not to mistakenly close the terminal which handles it, else you will close the channel for all other currently opened slave sessions. I wish ssh would fork and start the master on demand then close it when the last channel closes.[0] http://www.cmdln.org/2008/02/11/restricting-ssh-commands/ -----
If you're connecting from a *nix-y box, you may also be interested in sshuttle: https://github.com/apenwarr/sshuttleIt gives you most of the benefits of VPN, without requiring tun/tap and without needing root on the remote box -- all you need is the ability to run python. Very useful if you're on an insecure network and you want to tunnel everything over a secure connection, or if you have SSH access to a box inside your firewall and want to access other resources without having to specify each port individually. -----
> Ssh ControlMaster allowing to reuse connections can really improve responsiveness. Tip: start the master connection as a daemon (-f), so as not to mistakenly close the terminal which handles it, else you will close the channel for all other currently opened slave sessions. I wish ssh would fork and start the master on demand then close it when the last channel closes.Good news: as of OpenSSH 5.6p1, it can. Just set "ControlPersist 60" in ~/.ssh/config (in addition to setting ControlMaster auto and ControlPath), and ssh will automatically spawn an SSH master connection in the background, and close it 60 seconds after the last client exits. (You can obviously change the timeout to taste.) -----
> Ssh ControlMaster allowing to reuse connections can really improve responsiveness.Yes it does, but I've noticed when I do this, it breaks my rsnapshot backups. Is this something you've heard of or know a fix for? -----
I don't use rsnapshot but you can set up arguments you pass to ssh, in which case you can selectively disable ControlMaster. If you can't, maybe rsnapshot respects .ssh/config so you can set up a Host entry with the relevant config. If you want to also use ControlMaster the host you connect to with rsnapshot, you can set up a Host with a dummy name and set its Hostname option to the real host.-----
> I don't use rsnapshot but you can set up arguments you pass to ssh, in which case you can selectively disable ControlMasterJust FYI, that worked perfectly. -----
you don't mention whats awesome about the proxycommand to go through hosts:here's what! it uses the intermediate hosts as a tunnel, which means no ssh agent is listening on the hosts (the regular way to do this is ssh -A hostx ssh -A hosty ssh finalhost)
This means no attacker can use your agent while connected.Additionally, its less cumbersome when its setup. -----
Is there a "tech blogger of the year" category somewhere so we can nominate this guy? Every single one of his posts is epic. The peri-relational metaphor for shell command composition, this one, and every one before should be required reading.-----
Thanks for the kind words!These recent posts are part of the lecture notes for my "Scripting Language Design and Implementation" course.
There are slides that go along with some of them: http://matt.might.net/teaching/scripting-languages/spring-20...
I prefer spartan slides, so I'm not sure how useful they are without me presenting them.
But, I'll throw them out there since there are a few nuggets in them that are not in the posts.There are also slides for non-existent posts (e.g. bash), because I don't always have time to transcribe my notes into a blog post. -----
Hey Matt, to echo yycom's concern below... can you please add dates to your articles? We have context as they're posted today, but it gets muddled 10+ years out.-----
One addition:Re: iOS -- Panic (makers of Coda, etc.) developed a _really_ nice little iOS app for SSH called 'Prompt'. It got some coverage here when it was released, and I immediately replaced iSSH with it and haven't looked back once.http://www.panic.com/blog/2011/04/introducing-prompt-ssh-for... -----
scp has some end-to-end latency for each file transferred. This means that for lots of small files, a single tar file stream is much quicker than 'scp -r'.-----
The most fun I ever had was doing exactly this, piping a stream through ssh, but on the one end was a CD image, on the other end was a cd burner. It is kinda obvious you could also do that because pipes and ssh are ubiquitous on UNIX but I still couldn't stop giggling.-----
Using named pipes (mkfifo) I suspect you could do that. I've not tried it in practice and there will be some warts to work around. e.g. the password prompt comes to mind.-----
if you're piping the output of tar, instead of using "tar f -", you can leave off the f argument (since you don't want to specify a file anyway) and tar will default to stdin/stdout:
$ tar cz foo | ssh remote "cd /where/to/unpack && tar xz"
For GNU tar these days that's true, unless you can be sure $TAPE is in its environment. Historically, tar defaulted to a tape device, e.g. /dev/mt0, and you still find vestiges of that, e.g. OpenBSD defaults to /dev/rst0.IOW, specify "f -". :-) -----
I would add the use of the ControlMaster and ControlPath options for connection sharing, as well as keepalive settings for those cases where connections drop when idle.The remote port forwarding feature can be very handy. I've used a combination of ssh and daemontools to set up remote access to a machine behind a particularly nasty firewall. -----
And if your SSH client supports it ControlPersist. It keeps the shared connection around in case you're coming back. It's a fairly new feature though.-----
I tried enabling this and it seems that support for this on MacOS is pretty iffy. It's not too stable and my issues went away as soon as I disabled it.-----
yeah, been using that for a while, and its quite handy. I want to switch to the cryptostick tho, because having a pinpad/reader around sux.don't you have one of those? -----
My laptop has a built in smart card reader, and my desktop has a USB one plugged in with a hardware pin-pad.The cryptostick does look cool. I've come across it before. I like the smart card because I can just pop it in my wallet like a credit card.You can also get keyboards with built in smart card readers, where the numeric keypad has a mode to operate as a hardware pin pad (rather than sending the keypresses to the computer) I'm thinking of getting one of these at some point. -----
Do you know of anyone who sells them in the US? (or OpenPGP cards or any other Linux usable tokens for that matter?) or do I have to order them from Germany?-----
My main problem with sshfs lately has been that on a flakey connection it sometimes hangs irretrievably, often taking out the process trying to use it (usually emacs.)-----
Good list of useful configuration options. I'd also like to add the "Compression yes" option that you can add on a per-host basis, and this could save some bytes sent over the wire. To see how much it saved, invoke with verbose ("ssh -v"), and it outputs the number of bytes saved after the session ends.Another config option that has saved me a lot of time is the "ProxyCommand" option that lets you specify a command, whose stdin is used as a pipe to talk to a remote server. So, something like:
Host inside
ProxyCommand ssh gateway nc inside 22
Would allow you to just type "ssh inside" and ssh to a machine behind a gateway, without ssh-ing twice!
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