&gt; I Want to know what is the meaning of MaxStartups 10:30:60?

 

10: Number of unauthenticated connections before we start dropping

30: Percentage chance of dropping once we reach 10 (increases linearly for more than 10)

60: Maximum number of connections at which we start dropping everything

I want to redirect requests on two conditions using nginx. 

This doesn&#39;t work:

      if ($host = &#39;domain.com&#39; || $host = &#39;domain2.com&#39;){
        rewrite ^/(.*)$ http://www.domain.com/$1 permanent;
      }   

What is the correct way to do this?



nginx.conf redirect multiple conditions

Is there a way to set the default zoom level in Visual Studio 2010?  The problem is that I find font size 10 to be too small, but font size 11 is too big.  It just so happens that 90% zoom level with font size 11 gives the perfect size I am looking for.  I would like to be able to have VS automatically always zoom the editor to 90%.

Visual Studio 2010 default zoom level

Problem Is: Some SFTP connections are failing in customer environment
             But using sample code if i test with same server no connection is failed.
             may be in customer envi many parallel sftp connection started at a time.

I Want to know what is the meaning of MaxStartups 10:30:60

In the above i know only 10 , which means maximum unauthenticated ssh connection allowed.
means at same time 12 sssh connection request comes 2 request fail and 10 success.

What is the mean of 30 and 60 ?

In SSHD Configuration what does &quot;MaxStartups 10:30:60&quot; mean?

Problem Is: Some SFTP connections are failing in customer environment
But using sample code if i test with same server no connection is failed.
may be in customer envi many parallel sftp connection started at a time.
I Want to know what is the meaning of MaxStartups 10:30:60
In the above i know only 10 , which means maximum unauthenticated ssh connection allowed.
means at same time 12 sssh connection request comes 2 request fail and 10 success.
What is the mean of 30 and 60 ?

Some background info: I was looking to run a script on a Red Hat server to read some data from /dev/random and use the Perl unpack() command to convert it to a hex string for usage later on (benchmarking database operations).  I ran a few &quot;head -1&quot; on /dev/random and it seemed to be working out fine, but after calling it a few times, it would just kinda hang.  After a few minutes, it would finally output a small block of text, then finish.

I switched to /dev/urandom (I really didn&#39;t want to, its slower and I don&#39;t need that quality of randomness) and it worked fine for the first two or three calls, then it too began hang.
I was wondering if it was the &quot;head&quot; command that was bombing it, so I tried doing some simple I/O using Perl, and it too was hanging.
As a last ditch effort, I used the &quot;dd&quot; command to dump some info out of it directly to a file instead of to the terminal.  All I asked of it was 1mb of data, but it took 3 minutes to get ~400 bytes before I killed it.

I checked the process lists, CPU and memory were basically untouched.  What exactly could cause /dev/random to crap out like this and what can I do to prevent/fix it in the future?


*Edit:* Thanks for the help guys!  It seems that I had random and urandom mixed up.  I&#39;ve got the script up and running now.  Looks like I learned something new today. :)

/dev/random Extremely Slow?

is it possible to specify non-capturing groups in sed?

if so, how?

how do you specify non-capturing groups in sed?

I `screen -r`&#39;d into a Django server that&#39;s running and I can&#39;t simply &lt;kbd&gt;Ctrl&lt;/kbd&gt; + &lt;kbd&gt;C&lt;/kbd&gt; and `exit` out of it.

Are there any alternative ways to get out of `screen`?

Currently, I manually close the tab on my local PC and `ssh` back in, but that&#39;s becoming tiresome.


How do I get out of &#39;screen&#39; without typing &#39;exit&#39;?

Example `file.txt`:

      100 foo
      2 bar
      300 tuu

When using `sort -k 1,1 file.txt`, the order of lines will not change, though we are expecting :

      2 bar
      100 foo
      300 tuu

How to sort a field consisting of numbers based on the absolute numerical value?

How to sort a file, based on its numerical values for a field?

I was looking to find the difference between these four on Google and I expected there to be a huge amount of information on this, but there really wasn&#39;t any solid comparison between the four calls. 

I set about trying to compile a kind of basic at-a-glance look at the differences between these system calls and here&#39;s what I got. Is all this information correct/am I missing anything important ?

`Fork` : The fork call basically makes a duplicate of the current process, identical in almost every way (not everything is copied over, for example, resource limits in some implementations but the idea is to create as close a copy as possible).

The new process (child) gets a different process ID (PID) and has the PID of the old process (parent) as its parent PID (PPID). Because the two processes are now running exactly the same code, they can tell which is which by the return code of fork - the child gets 0, the parent gets the PID of the child. This is all, of course, assuming the fork call works - if not, no child is created and the parent gets an error code.

`Vfork` : The basic difference between vfork and fork is that when a new process is created with vfork(), the parent process is temporarily suspended, and the child process might borrow the parent&#39;s address space. This strange state of affairs continues until the child process either exits, or calls execve(), at which point the parent 
process continues. 

This means that the child process of a vfork() must be careful to avoid unexpectedly modifying variables of the parent process. In particular, the child process must not return from the function containing the vfork() call, and it must not call exit() (if it needs to exit, it should use _exit(); actually, this is also true for the child of a normal fork()). 

`Exec :` The exec call is a way to basically replace the entire current process with a new program. It loads the program into the current process space and runs it from the entry point. exec() replaces the current process with a the executable pointed by the function. Control never returns to the original program unless there is an exec() error.

`Clone :` Clone, as fork, creates a new process. Unlike fork, these calls allow the child process to share parts of its execution context with the calling process, such as the memory space, the table of file descriptors, and the table of signal handlers.

When the child process is created with clone, it executes the function application fn(arg). (This differs from fork, where execution continues in the child from the point of the original fork call.) The fn argument is a pointer to a function that is called by the child process at the beginning of its execution. The arg argument is passed to the fn function. 

When the fn(arg) function application returns, the child process terminates. The integer returned by fn is the exit code for the child process. The child process may also terminate explicitly by calling exit(2) or after receiving a fatal signal. 



Information gotten form : 

 - [https://stackoverflow.com/questions/1653340/exec-and-fork][1]
 - [http://www.allinterview.com/showanswers/59616.html][2]
 - [http://www.unixguide.net/unix/programming/1.1.2.shtml][3]
 - [http://linux.about.com/library/cmd/blcmdl2_clone.htm][4]


Thanks for taking the time to read this ! :)


  [1]: https://stackoverflow.com/questions/1653340/exec-and-fork
  [2]: http://www.allinterview.com/showanswers/59616.html
  [3]: http://www.unixguide.net/unix/programming/1.1.2.shtml
  [4]: http://linux.about.com/library/cmd/blcmdl2_clone.htm

The difference between fork(), vfork(), exec() and clone()

This seems to be a common problem but my specific case seems a little different.

I set up a new Amazon EC2 instance using the command line tools and connected via SSH and did some configuration work. 

Initially, though, I couldn&#39;t ssh on to the instance, I had to stop and restart the instance, then i could connect. Before restarting I just got the response.

    Permission denied (publickey).

That was last night, this morning I go back to the same instance and now all I get is

    Permission denied (publickey).

I&#39;ve tried rebooting the instance with no joy.

Can anyone point me in the right direction here? The same command that worked last night no longer works, I&#39;m connecting from my Macbook Pro.

Amazon EC2 Permission denied (publickey)

I try to push changes from my local repo to a remote repo. When I type:

    git push origin

I get the following error:

    The server&#39;s host key is not cached in the registry. You
    have no guarantee that the server is the computer you
    think it is.
    The server&#39;s rsa2 key fingerprint is:
    ssh-rsa 2048 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
    Connection abandoned.
    fatal: The remote end hung up unexpectedly

How can I solve this? I&#39;m using git from the command line in Windows 7.

**Edit**

When I try to do a simple ssh

    ssh user@hostname

I get the following error:

    Could not create directory &#39;/c//%HOMEDRIVE%%HOMEPATH%/.ssh&#39;.
    percent_expand: unknown key %H

Somehow it will not create the directory, because the path is invalid. How to fix this?

@eckes: **Edit2**

My Home is set to `%HOMEDRIVE%%HOMEPATH%` is this correct?

git - Server host key not cached

I am using [JSch][1] for sftp communication, now i want to use facilitate the key-based authentication, key is loaded on client and server machine once by my network team and all later communication would be only user based for which we have loaded the key.

    sftp -oPort=10022 jmark@192.18.0.246

as `tjill@192.18.0.135`

like this command work fine and connect to the sftp, how i can achieve this functionality programmatically.

if it is not possible using JSch, please suggest some other library. I came across [Apache SSHD][2].


  [1]: http://www.jcraft.com/jsch/
  [2]: http://mina.apache.org/sshd/

Can we use JSch for SSH key-based communication?

I&#39;m executing a script connecting via password-less SSH on a remote host. I want to set a timeout, so that if the remote host is taking an infinite time to run, I want to come out of that ssh session and continue other lines in my sh script.

How can I set a timeout?

How to set ssh timeout?

I&#39;m trying to connect to Amazon EC2 using OpenSSH in windows but I need to set the permissions of my key file.

What is the windows equivalent of `CHMOD 600`?

I&#39;ve googled extensively and found only blogspam.

EDIT: Windows 7, using DOS.

Windows CHMOD 600

I need to transfer a log file to a remote host using [sftp][1] from a Linux host. I have been provided credentials for the same from my operations group. However, since I don&#39;t have control over other host, I cannot generate and share RSA keys with the other host. 

So is there a way to run the `sftp` command (with the username/password provided) from inside the Bash script through a [cron][2] job?

I found a similar Stack Overflow question, *[Specify password to sftp in a Bash script][3]*, but there was no satisfactory answer to my problem.

  [1]: http://en.wikipedia.org/wiki/Secure_file_transfer_program
  [2]: http://en.wikipedia.org/wiki/Cron
  [3]: https://stackoverflow.com/questions/5268865


How to run the sftp command with a password from Bash script?

I&#39;m logged into a remote host using PuTTY. 

What is the command to transfer files from my local machine to the machine I&#39;m logged into on PuTTY?

Transfer files to/from session I&#39;m logged in with PuTTY

I manually copy a file to a server, and the same one to an SFTP server.
The file is 140MB.

FTP: I have a rate arround 11MB/s

SFTP: I have a rate arround 4.5MB/s

I understand the file has to be encrypted before being sent. Is it the only impact on the file transfer? (and actually this is not exactly transfer time, but encryption time).

I am suprised of such results.

Why when I transfer a file through SFTP, it takes longer than FTP?

I have tried `put -r directory/*`, which only uploaded the files and not folders. Gave me the error, cannot `Couldn&#39;t canonicalise`. 

Any help would be greatly appreciated.

How can I upload an entire folder, that contains other folders, using sftp on linux?

In the past I used SSHFS to mount drives, so I could easily work on remote machines with software from my machine. However, when I was at the MacFUSE project page, I noticed that SSHFS has been long since deprecated.

What are people using with Mountain Lion to mount drives? Is it built-in to OSX yet, or has some other project completely replaced the functionality brought to us by SSHFS?

Any suggestions are greatly appreciated.

EDIT: In the past I used &quot;SSHFS GUI&quot; to mount drives. It looks very similar to the the `Finder &gt;&gt; Go &gt;&gt; Connect to server...` interface.

+1 -&gt; m01 - I&#39;m currently using your solution, but if anyone knows a GUI I would love to hear about it.

SSHFS for OSX 10.8 (Mountain Lion)

EDIT: Putting exactly what was done

I need to SSH localhost without password, the usual way of doing it (with public keys) do not work.

    user@PC:~$ rm -rf .ssh/*
    user@PC:~$ ssh-keygen -t rsa &gt; /dev/null 
    Enter file in which to save the key (/home/user/.ssh/id_rsa): 
    Enter passphrase (empty for no passphrase): 
    Enter same passphrase again: 
    user@PC:~$ ls .ssh/
    id_rsa  id_rsa.pub
    user@PC:~$ ssh-copy-id -i localhost 
    The authenticity of host &#39;localhost (::1)&#39; can&#39;t be established.
    RSA key fingerprint is f7:87:b5:4e:31:a1:72:11:8e:5f:d2:61:bd:b3:40:1a.
    Are you sure you want to continue connecting (yes/no)? yes
    Warning: Permanently added &#39;localhost&#39; (RSA) to the list of known hosts.
    user@localhost&#39;s password: 
    Now try logging into the machine, with &quot;ssh &#39;localhost&#39;&quot;, and check in:
    
      .ssh/authorized_keys
    
    to make sure we haven&#39;t added extra keys that you weren&#39;t expecting.
    
    user@PC:~$ ssh-agent $SHELL
    user@PC:~$ ssh-add -L
    The agent has no identities.
    user@PC:~$ ssh-add 
    Identity added: /home/user/.ssh/id_rsa (/home/user/.ssh/id_rsa)
    user@PC:~$ ssh-add -L
    ssh-rsa ...MY KEY HERE

    user@PC:~$ ssh-copy-id -i localhost 
    user@localhost&#39;s password: 
    Now try logging into the machine, with &quot;ssh &#39;localhost&#39;&quot;, and check in:
    
      .ssh/authorized_keys
    
    to make sure we haven&#39;t added extra keys that you weren&#39;t expecting.
    
    user@PC:~$ ssh localhost echo &#39;testing&#39;
    user@localhost&#39;s password: 
    
    user@PC:~$ 

 
So as you can see in the last command it is still asking the password!
How can I fix that? Ubuntu-10.04, OpenSSH_5.3p1


EDIT2:

Adding some info about the sshd


    user@PC:~$ cat /etc/ssh/sshd_config | grep Authentication
    # Authentication:
    RSAAuthentication yes
    PubkeyAuthentication yes
    RhostsRSAAuthentication no
    HostbasedAuthentication no
    # Uncomment if you don&#39;t trust ~/.ssh/known_hosts for RhostsRSAAuthentication
    ChallengeResponseAuthentication no
    # PasswordAuthentication yes
 

EDIT3: Ading result from $ssh -vv localhost

    $ssh -vv localhost
    ...
    debug1: Authentications that can continue: publickey,password
    debug1: Next authentication method: publickey
    debug1: Trying private key: /home/user/.ssh/identity
    debug1: Offering public key: /home/user/.ssh/id_rsa
    debug2: we sent a publickey packet, wait for reply
    debug1: Authentications that can continue: publickey,password
    debug1: Trying private key: /home/user/.ssh/id_dsa
    debug2: we did not send a packet, disable method
    debug1: Next authentication method: password
    user@localhost&#39;s password: 


How to ssh to localhost without password?

I&#39;m unable to ssh and rysnc to a remote system. It keeps giving this error message:




    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     
          
    IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
    Someone could be eavesdropping on you right now (man-in-the-middle attack)!
    It is also possible that a host key has just been changed.
    The fingerprint for the RSA key sent by the remote host is
    a3:8f:7c:07:c9:12:d8:aa:cd:c2:ba:b3:27:68:bc:c2.
    Please contact your system administrator.
    Add correct host key in /root/.ssh/known_hosts to get rid of this message.
    Offending RSA key in /root/.ssh/known_hosts:8
    RSA host key for xxx.xxx.xxx.xxx has changed and you have requested strict checking.
    Host key verification failed.
    rsync: connection unexpectedly closed (0 bytes received so far) [sender]
    rsync error: unexplained error (code 255) at io.c(601) [sender=3.0.8]

I&#39;ve removed `authorized_keys` file from `/home/user/.ssh`.

Ubuntu-ssh - - WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED

I see stuff all over Google on how to see the RSA key fingerprint, but not the ECDSA fingerprint.

What command do I use to see what the ECDSA key fingerprint of my server is?

I need to create a script that automatically inputs a password to OpenSSH `ssh` client.

Let&#39;s say I need to SSH into `myname@somehost` with the password `a1234b`.

I&#39;ve already tried...

    #~/bin/myssh.sh
    ssh myname@somehost
    a1234b

...but this does not work.

How can I get this functionality into a script?

Automatically enter SSH password with script

I am having issues setting up OpenSSH for Windows, using public key authentication.

I have this working on my local desktop and can ssh with a key from Unix machines or other OpenSSH for Windows machines.

I have replicated the build onto a server, I can get password authentication working fine, but when I use the keys I get the following issue:

    debug1: Authentications that can continue: publickey,password,keyboard-interactive
    debug3: start over, passed a different list publickey,password,keyboard-interactive
    debug3: preferred publickey,keyboard-interactive,password
    debug3: authmethod_lookup publickey
    debug3: remaining preferred: keyboard-interactive,password
    debug3: authmethod_is_enabled publickey
    debug1: Next authentication method: publickey
    debug1: Offering RSA public key: /cygdrive/c/sshusers/jsadmint2232/.ssh/id_rsa
    debug3: send_pubkey_test
    debug2: we sent a publickey packet, wait for reply
    Connection closed by 127.0.0.1

So for the purposes of testing, I have been just trying to SSH to localhost, but even when tried remotely I get the same issue.

Even more strange, is that when I have both password and public key enabled in `sshd_config`, it will only attempt to use keys and then bomb out with the above message and won&#39;t even try to use password.

Here are the steps I have taken:

1. Install OpenSSH for Windows
2. `mkgroup -l &gt;&gt;..\etc\group` (added local groups)
3. `mkgroup -d &gt;&gt;..\etc\group` (added domain groups)
4. `mkpasswd -L -u openssh &gt;&gt;..\passwd` (added my local user)
5. `mkpasswd -D -u jsadmint2232 &gt;&gt;..\passwd` (added my domain user)
6. Edited the homedir in file *passwd* to point to c:\sshusers\%USER% - where %USER% is the user name
7. Enabled password authentication, disabled key authentication
8. Created SSH keys for both jsadmint2232 / OpenSSH and ensured that the files were created in home directories
9. Added authorized_keys files into .ssh directories for each user and added keys for incoming connecting users
10. `net stop opensshd` / `net start opensshd`
11. Test if password authentication works both locally and remotely
12. Updated sshd_config, to enabled key auth - restart opensshd
13. Test connection and get above error. Also, it doesn&#39;t even try password authentication.
14. Updated sshd_config, to disable password authentication completely - restart opensshd
15. Test connection and still get above error

It appears the server is killing the connection for some reason.


Setting up OpenSSH for Windows using public key authentication

I realize this question has already been asked in some different ways, however it doesn&#39;t seem like any of the ways I&#39;ve come across have worked to fix this problem, so here it goes:

I&#39;m trying to connect to my raspberry pi 3 raspbian setup via ssh on my laptop, but although I have the correct ip address, I keep getting the error: 
        
    ssh: connect to host xxx.xxx.xx.x port 22: connection refused.

This is unusual because when I try to ping that address, it works fine. Is there anything I can try to figure out what&#39;s wrong? 

Also keep in mind I am relatively inexperienced with bash in linux, so inclusion of any specific commands with a description of what they do would be greatly appreciated.

Content Type	Original Author	Original Content on Stackoverflow
Question	Syedsma	View Question on Stackoverflow
Solution 1 - Linux	phooji	View Answer on Stackoverflow

In SSHD Configuration what does "MaxStartups 10:30:60" mean?

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Visual Studio 2010 default zoom level

nginx.conf redirect multiple conditions

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