Lets say I have an Emacs-Server running on some remote server, with all the libraries and software necessary for running my application.
Then I want several clients to connect to that remote machine, using Emacs-client. Does each client need a full Emacs installation, or is there a minimal installation that is just enough to communicate with the remote server, where all the action is?
Could this (Emacs-)client installation be so minimal, that almost all software-updates can be done on the server, without affecting the Emacs-clients?
Is there a reason not to run the clients remotely as well, and simply use a local display? That way, pretty much all you need on the local machines is the ssh client and the X Window server.
ssh -X (user)#(server) "emacsclient -c"
Edits for the comments:
This command starts a new client to connect to an existing Emacs server (which it assumes is already running). You can use "emacsclient -a '' -c" to automatically start emacs --daemon if there is no existing server, but I don't know whether you want the connecting user to be starting the server.
In fact, I'm pretty unsure about the whole multi-user side of this to be honest, as I've never done that before. Authentication for the above is handled by ssh, but there may well be subsequent permission issues to deal with, or similar, when the server and the clients are started by different users.
This approach should be possible with Windows/Cygwin as client and/or server, as Cygwin provides Emacs, OpenSSH, and X.org packages. (I regularly use Windows/Cygwin as a local display for Emacs running on Linux.) It may be harder to set up, though, and any permissions issues are probably different when you're using Cygwin.
I'm less sure how this would work without Cygwin. NTEmacs certainly won't talk to X.org, so I imagine you'd be terminal based in that instance. (There are probably other options, but Cygwin sounds to me like the best-integrated approach to using all of Emacs, SSH, and X on Windows).
Lastly, I imagine you're probably getting your "Connection refused" error because localhost is not running a sshd daemon? I would say that configuration of ssh is outside the scope of this question, but there are lots of resources online for that.
Depending on what you're trying to achieve, you may be able to use a combination of Emacs and Screen. By starting up Emacs from Screen on the remote machine and detaching from it, you can subsequently re-attach from a different machine that doesn't have Emacs. Again, whether this will work for you or not depends on what you're trying to do; however, for many Emacs use-cases, this can be very effective. If you're not familiar with using Screen in this manner, here is some reading material:
screen - The Terminal Multiplexer
I am not sure that would be possible. emacsclient uses tramp to connect to a remote server, and just by looking at the number of requires in the tramp elisp files (41) it seems very unlikely. You can try it yourself with the following:
zgrep -oE "\(require '[a-z-]+\)" *el.gz | sed -e 's%[a-z0-9-]\+\.el\.gz:%%g' | sort | uniq -cu | wc -l
I'm not an expert in emacsclient, but I don't think is was designed to do what you're looking for. I think the general use case is that emacsclient allows you to redirect new requests to open a file with emacs to a persistent emacs process to avoid what may be a bit of an overhead in startup time. You seem to be looking for more of a true client/server relationship.
I think to meet the goal you're aiming at you'll probably need to look a little outside emacs, probably a project unto itself - 'emacsRemoteClient. It boils down to one or two models; the file you want to edit would need to have it's path sent over to the server machine so that emacs could do some sort of remote tramp access & then spawn the xwindow locally (using the local X env or requiring an x server on windows)... or two, transferring the file to some temp location on the server box and again spawning the remote x window locally (followed by syncing the changes between the tmp & local file).
Would be cool to have something like that... but suspecting it'll involve a bit of work. Maybe we just need a version of emacs written in javascript and it can live in the cloud or on your browser... oh to have emacs keybindings in the browser ;-)
-Steve
Related
I am working on a remote Linux machine a little complex right now. Firstly, I use Putty to login a jump machine which is also a Linux system in my office, then I use command go to jump to the remote machine outside of my office. There is also a key file I need when using putty. The Linux jump command is like this:
ssh 119.11.11.11 -p 22
The IP should be changed according to the remote machine IP.
The usual way of my development is always using Emacs Tramp to edit files remotely.
I don't want to copy my Emacs config files to the remote machine, for it is a little bit hard to sync the config files between machines. I also don't want to download the files to local for it isn't conveniently to debug.
In this suitation, how can I use Emacs to jump to the remote machine? Is it possible to do the jump by using Cygwin, Putty or something else?
My desktop is Windows 7, and my Emacs is 24.2
Assuming you can't SSH directly to the destination server, it sounds like you could resolve this by configuring a multi-hop proxy for tramp.
I've only tried that once, but it was for a slightly different situation, and I had problems getting it working; so I'll just point you at the documentation, and leave it to someone more knowledgeable to provide other details if need be.
C-hig (tramp) Multi-hops RET
I would strongly recommend using either scpc or rsyncc as the method for the second hop, if possible, as that will automatically utilise SSH ControlMaster to keep the connection open, which dramatically improves Tramp performance.
I'm not sure whether or not there's an equivalent to that for PuTTY/plink? I do know that Cygwin isn't able to support ControlMaster for some technical reasons (or at least this was the case a few years ago), so using that probably wouldn't help.
Another alternative Cygwin's SSH and PuTTY is to host a Linux(*) VM on your Windows box and run Emacs inside that (which means you can use Linux's SSH and ControlMaster). Cygwin can provide an X display in that instance. That's complicating matters, of course, so I would certainly try out the simpler options first; but if performance is lacking, and your local PC is reasonably powerful, the VM approach might surprise you.
* or similar
Ignoring Tramp entirely, sshfs is often used to mount a remote filesystem locally, in which case Emacs doesn't even know that it's talking to a remote server. I've never used it myself, and certainly not on Windows, but it could be worth a look as well.
I have a large repository of C++ code on a remote cluster (linux OS). When I need to work on this code from my home computer (Ubuntu OS), I try to access these codes through emacs on X windows. However the X window connection is very slow making the editing a painful process. So I sometimes move files manually between my local drive and remote cluster to edit the files. My question is: is there a way to configure my local emacs, such that when I edit the file in my local space, it would automatically be backed up in the cluster where it can then be compiled?
UPDATE:1
I installed TRAMP and it works well for servers that can be connected directly. However I also have servers which can be connected only when I activate VPN. How to provide the VPN information to TRAMP to connect to this server?
The other question I had was how to stop the TRAMP when it waits for prompts from remote shell without having to kill the whole emacs buffer.
This is typically a use case where TRAMP would be useful.
Instead of connecting to the server using SSH and opening Emacs there with X forwarding, run Emacs on your box and open your files remotely using TRAMP. For example:
C-xC-f/ssh:user#host:/remote/path/to/the/fileRET
This way, your Emacs process runs locally, but all file operations (e.g. save, revert, ...) are forwarded to the server, and all shell commands issued from TRAMP buffers also run on the remote server (this includes M-x compile)
UPDATE:1
When TRAMP hangs waiting for a remote shell prompt (which tends to happen frequently for reasons which are still obscure to me), I usually kill the underlying ssh process (htop with tree-like view is a good tool to do this) . TRAMP notices this and automatically respawns the killed process to resume operations.
Wouldn't it be easier to run Emacs in a console on the remote server? All Emacs functions can be access via the keyboard and once you get used to the key combinations it usually works out faster.
That way you will be running faster than forwarding an X session - running in a console is what Emacs was designed for.
As an added bonus - if you get used to using Gnu screen - http://www.gnu.org/software/screen/ you can pick up your sessions exactly as they were if the connection drops. In fact with screen you can shutdown your laptop at the end of the day - login over SSH the next day and pick up all your 'screens' exactly as they were the day before. This will include any open editors, debug sessions etc.
Gnu screen is available as a package on Debian and probably most Linux distributions.
I am having a conflict of ideas with a script I am working on. The conflict is I have to read a bunch of lines of code from a VMware file. As of now I just use SSH to probe every file for each virtual machine while the file stays on the server. The reason I am now thinking this is a problem is because I have 10 virtual machines and about 4 files that I probe for filepaths and such. This opens a new SSH channel every time I refer to the ssh object I have created using Net::OpenSSH. When all is said and done I have probably opened about 16-20 ssh objects. Would it just be easier in a lot of ways if I SCP'd the files over to the machine that needs to process them and then have most of the work done on the local side. The script I am making is a backup script for ESXi and it will end up storing the files anyway, the ones that I need to read from.
Any opinion would be most helpful.
If the VM's do the work locally, it's probably better in the long run.
In the short term, the ~equal amount of resources will be used, but if you were to migrate these instances to other hardware, then of course you'd see gains from the processing distribution.
Also from a maintenance perspective, it's probably more convenient for each VM to host the local process, since I'd imagine that if you need to tweak it for a specific box, it would make more sense to keep it there.
Aside from the scalability benefits, there isn't really any other pros/cons.
This page from the Emacs manual describes a function called make-frame-on-display that allows you to access a remote Emacs session. My interest in this function is to use it to share buffers for pair programming remotely with a colleague.
From the page:
It is even possible to use this feature to let two or more users type simultaneously on the two displays, within the same Emacs job. In practice, however, the different users can easily interfere with each others' edits if they are not careful.
How exactly do I set this up? What do I need? What does my partner need? The details are not stated, but I don't know enough about Emacs to know where to start.
Is there any other way to get a shared Emacs session? This page from the Emacs Wiki refers to something called multi-tty. The questions I asked above also apply to this.
Which is better: multi-tty or make-frame-on-display?
I haven't tried multi-tty, but make-frame-on-display is pretty simple. You type M-x make-frame-on-display, hit return, then type the display you want the frame to show up on. For example:
I have my local host (thor) running emacs and I want to make a frame pop up on a machine called zeus, on its only X display (0.0). So I would type M-x make-frame-on-display<ret>zeus:0.0<ret>
All set!
You may need to configure the remote machine's X server to accept incoming connections from your machine with "xhost +thor". You may also need to configure its firewall to allow incoming connections on the X11 port, which is 6000. Keep in mind that X forwarding is not encrypted, so if you aren't working with someone on your LAN you may want to go through a VPN in order to keep things private.
Edited to fix brackets.
You can also have the person at zeus type ssh -X thor emacsclient -c.
Did you ever consider using GNU screen on a shared account for pair programming? It's dead easy to get it to work and you get to pick any console based editor you and your partner like (emacs, vim, joe, nano, zile, ...). However, this does of course not work with editors that cannot run inside a terminal.
To set it up, create a shared account on a computer running ssh. Then both log in to that account. One of the partners starts screen with
screen
and the other connects to it with
screen -x
where -x means "attach to a not detached screen session". The users can detach from their sessions w/ "C-a d".
Old question, new solution for anyone landed on this page from year 2016.
I set this up in Ubuntu 14.04 and it works perfectly:
Suppose I want to co-edit or demo some cool stuffs on emacs with my colleague Joe on the other end of the world.
Make sure an ssh server with emacs installed at either end. That is, either MyPC or JoePC must be a SSH server and have Emacs installed. From now on, let's say I asked Joe to install SSH server and Emacs on his computer.
Make sure byobu is installed on JoePC. Byobu supports both tmux and screen as backends (I prefer tmux for a more mordern and feature-rich).
I connect to JoePC with ssh remoteuser#joepc. No need for X-forwarding.
Open emacs from byobu-ssh terminal: TERM=xterm-256color && emacsclient --alternate-editor="" -t. One can make an alias for this command. I recommend this long command because it enables both better color support in the terminal and running Emacs in daemon mode. The daemon mode make it fast to close and reopen frames.
Now the magic unfold: Ask Joe to login with the same remoteuser I am loggin in; open the terminal and start byobu if it hasn't for him.
Start hacking or fumbling :-)
Comment:
Because the way byobu work. This approach works for any other program inside the byobu terminal.
This setup performs much better than Teamviewer or any other GUI remote desktop solutions.
Because the connection is through ssh to the remote server directly, it is as secure as the ssh conenction can offer.
I have a Perl Expect.pm script that does some moderately complex stuff like packaging applications, deploying the application, checking for logs, etc. on multiple remote unix hosts.
My predecessor had written similar scripts using rsh.
Is there a better approach between the two? Or should I use something all together different?
I am guessing somebody will bring up SSH; it's basically replacement for rsh, right? Unfortunately, however SSH is not an option for me right now.
Another thing I should add is that after logging in I need to be able to SUDO to a particular user to do most of the actions on the remote hosts.
Another thing I should add is that after logging in I need to be able to SUDO to a particular user to do most of the actions on the remote hosts.
To address this one particular point: using rsh (or ssh) you can specify which user to become in the remote session:
$ rsh -l username hostname
There's no need to use sudo in this case. Now would definitely be the time to look into ssh due to security issues. The syntax is the same, but ssh also allows a slightly different (and I'd say better) syntax:
$ ssh username#hostname
I found expect to be too finicky, but my experience with it is not substantial.
They do different things. Expect is a way to script what would otherwise be manual responses. rsh -- remote shell, not restricted shell, an unfortunate name clash -- allows you to run commands remotely on another system.
That said, the security holes and other disadvantages of using rsh to do remote commands, run sudo, etc, are immense.
I can see multiple ways of doing this:
Expect over telnet, rsh, or ssh
pros: single connection, fewer escaping issues
cons: fragility in a changing environment
rsh/ssh each command individually
pros: fewer escaping issues, more reliable in a changing environment
cons: each connection takes time for authentication, and, for ssh, handshaking the encryption
rsh/ssh all commands at once
pros: single connection (less overhead), more reliable than expect
cons: fragility in maintenance especially as you get more than a handful of statements in there, escaping issues are more prevalent (escape in perl so that it's still escaped by rsh/ssh so that it's still escaped by the remote shell so that it's properly handled by the sudo'd remote shell?)
rsh/ssh and run a script
pros: single connection, more reliable, more maintainable
cons: finding a way to get it over there (rcp/scp work, NFS works, you need to determine the best way for you).
All things considered, this is the most minor con as you could simply do something like
open my $fh, "|ssh user#host 'cat > /tmp/myscript'";
print $fh $script;
system qw(ssh user#host), "chmod u+x /tmp/myscript; /tmp/myscript; rm /tmp/myscript";
Of course, you'd add in some error handling (failed open, what if /tmp/myscript exists, etc.), but that's the idea.
Given a choice between rsh and telnet via expect, I would chose rsh. Expect scripts are fragile. All it takes to break one is someone changing the value of PS1 on the remote machine. Using rsh also prepares you for the day you will finally enter the '90s and start using ssh (since you can mostly just change rcp to scp and rsh to ssh and everything still works).