We have a remote Xen server running a lot of guest machines (on Linux), with only a couple of IPs available.  Each guest machine should be directly accessible by the SSH from the outer world.  Right now we assign a separate domain name to each guest machine, pointing to one of the few available IPs. We also assign a port number to that guest machine.  So, to access machine named foo, one should do as follows:   $ ssh foo.example.com -p 12345   ...And to access machine named bar:   $ ssh bar.example.com -p 12346   Both foo.example.com and bar.example.com point to the same IP.  Is it possible to somehow get rid of custom ports in this configuration and configure SSH server, listening at that IP (or firewall or whatever on server side), so it would route the incoming connection to the correct guest machine, based on the domain address, so that following works as intended?   $ ssh foo.example.com hostname # prints foo $ ssh bar.example.com hostname # prints bar   Note that I do know about .ssh/config and related client-side configuration solutions, we're using that now. This question is specifically about a zero client configuration solution.
I've grown quite fond of HTTP reverse proxies in our development environment and found the DNS based virtual host reverse proxy quite useful. Having only one port (and the standard one) open on the firewall makes it much easier for management.  I'd like to find something similar to do SSH connections but haven't had much luck. I'd prefer not to simply use SSH tunneling since that requires opening port ranges other than the standard. Is there anything out there that can do this?  Could HAProxy do this?
I am trying to help a friend who is very concerned that she has just lost all of the data on her 32GB SanDisk microSD card.  I told her I would post this and see if anyone could offer help.  Here are the details:   The SanDisk microSD card is less than two years old.  Probably only about a year old.  The store will take it back, but that doesn't really help.  She wants her data. She used the card in her Samsung Galaxy S4 smartphone for over a month.  The phone was never exposed to water or temperature extremes. Today, her phone suddenly said something like "Your SD card is blank or an unsupported format". Her phone was then unable to read the SanDisk microSD card at all.   Here's what she has tried:   Rebooting her phone.  Had no effect. Taking out the SanDisk microSD card and putting it inside a full-size SD card adapter, and inserting it into a Windows 7 SP1 computer.  The computer did not recognize its presence at all. Putting the SanDisk microSD card into a USB 2.0 external card reader and inserting the card reader into a USB port on a Windows 7 SP1 computer.  The computer recognized the card reader and installed drivers for it.  The card reader shows up as 'Removable Disk' in Windows Explorer.  Clicking on 'Removable Disk' in Windows Explorer results in the error "Insert disk: Please insert a disk into the Removable Disk". After trying #3, tried opening the 'Removable Disk' in FreeCommander.  Doing so results in the error "The device is not ready".   She does not have access to a linux box, but does have access to her Android phone.  What can she do to recover the data on her 32GB SanDisk microSD card? Digitizing Free Satellite Imagery in QGIS without getting Alignment issues with Openlayers Plugin Lightning - dynamically creating force:inputField I initially thought that dark energy must in some way violate conservation of mass and energy since the component of the energy density of space that comes from dark energy is constant, and space is expanding. Therefore, as space expands the energy in the universe that comes from dark energy would increase. I presumed the source of this energy was not coming from the conversion of other types of energy to dark energy, so it must violate conservation.  I decided to Google this and came upon this article:    It says that dark energy does NOT violate conservation and quotes Carroll, Press, and Turner (1992):  "…the patch does negative work on its surroundings, because it has negative pressure. Assuming the patch expands adiabatically [i.e. without loss or gain of heat], one may equate this negative work to the increase of mass/energy of the patch. One thereby recovers the correct equation of state for dark energy: P = – ρ c2. So the mathematics is consistent."  Is there a way to explain this in layman's terms? (The blog attempted to do this, but it was very unclear to me.) More specifically, can you explain where my initial train of thought described above fails when I erroneously concluded that dark energy violates conservation?  Thank you. In BibTeX, I need to cite another entry as a note/comment of a first one, something like:  @article{Paper1, author = {Author A.}, journal = {The Journal of XX}, number = {1}, pages = {4252}, year = {2000}, note = {see updated results in \cite{Paper2}    } }  @article{Paper2, author = {Author B.}, journal = {The Journal of YY}, number = {2}, pages = {1}, year = {2001} }   Could you give a suggestion in doing this?  I think my need is not really fitting to what proposed here: How to make a field NULL using MySQL GUI Tools? I'm using the MySQL Query Browser (part of the ) and need to change a field to NULL, but I can't figure out how to do it - if I delete the value it tries to update it to ''. Typing "NULL" makes it try to update to 'NULL' (a string).  I know I could just write a query to do it, but that defeats the entire purpose of the tool, no? Sending an E-mail to all addresses of all contacts in a contact group in Gmail I'm trying to send an E-mail message using Gmail to a contact group where some of the contacts have more than one E-mail address and I want to send the mail to all of them.   Is there a way for me to do that? Shine a light into a superconductor A type-I superconductor can expel almost all magnetic flux (below some critical value $H_c$) from its interior when superconducting. Light as we know is an electromagnetic wave. So what would happen if we shine a light deep into a type-I superconductor? Suppose the magnetic field of the light is significantly lower than $H_c$.  And what about type-II superconductors? How do I install and manage RPMs? Particle energy in general relativity? Assume that a particle is moving with four-velocity $u^\mu$ through a spacetime with metric $g_{\mu\nu}$ ($-+++$ signature).  Let us also assume that there exists a time-like vector field $t^\mu=(1,0,0,0)$.  Is it generally true that the energy $E$ of a particle is given by the following expression:  \begin{eqnarray*} E &amp;=&amp; -mt_\mu u^\mu\\ &amp;=&amp; -mg_{\mu\nu} t^\nu u^\mu\\ &amp;=&amp; -mg_{00}u^0\\ &amp;=&amp; -mg_{00}\frac{dt}{d\tau}? \end{eqnarray*}  In the special case that $t^\mu$ is a Killing vector and $u^\mu$ is tangent to a geodesic then $E$ is a constant of motion of the particle. But the energy of a particle need not remain constant in the general case - is that true?  If $E=-mt_\mu u^\mu$ is indeed the particle mass/energy then does it act as a source of spacetime curvature given that it depends on the $00$-component of the spacetime metric ifself? I suppose that is not a problem. Why can a 1 element set be a member of another set but not a subset of it? I have came across this in a textbook:     $\{2\}\nsubseteq\{\{2\}\}$ but $\{2\}\in\{\{2\}\}$   I understand that $\{2\}$ is an element (member) of the other set but considering $\{2\}$ is a set itself, why is it not a subset? What is the significance of the name Bleach? The name "Bleach" seems to be having no relevance to the plot unlike most other series. Was it just chosen at Kubo-sensei's whim or does it have some significance? Maybe some cultural significance associated with shinigami, etc. that I am now aware of? Does Hilbert's $\varepsilon$-calculus have any real problem when using for incomplete systems? Association Bonus not removed upon account deletion Recently a user asked a question on Meta asking about his deleted account (I won't draw attention to him or his question unless it is really necessary but shouldn't be hard to find - at least until the question gets deleted1 as I don't know if it is relevant to this question).  However, while looking at his account, it appears as if he received the association bonus on all of his accounts, including the new Stack Overflow account he just created, but does not have any account with >200 rep.    The most likely scenario is that the deleted account had more than 200 rep and triggered  the association bonus, but that leads to 2 questions:   Why did his previously associated accounts retain the association bonus? Why did he get an association bonus on his brand new account?   Is this a  or ?  1 - The post in question was deleted by the OP several hours ago but before then the account was confirmed by a mod to be deleted due violations of a sock puppety nature (which I think everyone suspected at the time).  Given that the account in question was a sock puppet, I think it highlights an important reason for removing the association bonus when the account that triggered the bonus is deleted.  Theoretically, as long as he keeps getting the association bonus, he can go to any site and already have more than enough privileges to do damage. I found a good replacement IDE for Delphi called Lazarus. But I don't have a question for programmers.  Will the statically linked Linux binary work on all Linux distributions? I.e. it does not matter on what Linux distro I built it and it will work on Debian / ArchLinux / Ubuntu / OpenSUSE / ... whatever?  As a result of my findings, does really only matter 32bit vs 64bit? I want to be sure before I publish. Is GTA Online cross-platform? Grand Theft Auto Online exists on five different platforms: XBox 360, PS3, XBox One, PS4, and PC. Do any of these play on the same servers, allowing people on differing platforms to play together? Solving an equation over the reals: $ x^3 + 1 = 2\sqrt[3]{{2x - 1}}$ Solve the following equation over the reals:$$ x^3  + 1 = 2\sqrt[3]{{2x - 1}} $$ I noticed that 1 is a trivial solution, then I tried raising the equation to the 3rd, then dividing the polynomial by $(x-1)$.. But I can't see the solution, how do I go from here? I was wondering why a laser beam diverges. If all the photons are in the same direction, I would imagine that it would stay that way over a long distance. I am aware that a perfectly collimated beam with no divergence cannot be created due to diffraction, but I am looking for an explanation based on  photons rather than wave physics. Why do ICs have NC (No Connection or No Function) pins? How can I limit ssh *remote* port forwarding? I need to limit which ports can be remotely 'ssh -R' forwarded by an user.  I know about permitopen option on authorized_keys, but as it says on man page it only limits local 'ssh -L' port forwarding  As discussed  a user would get the same with netcat or similar, but in this case user has no shell access  I also found  that talks about using selinux or LD_PRELOAD, but I never configured selinux before and can't find info on how to do that with LD_PRELOAD.  maybe someone have made a patch for openssh to implement that?  EDIT: I've found  so I guess it's not yet implemented