ssh command

I am a new Linux user. I use scp to upload files to net-storage provided CDN company. I do not want to overwrite the existing files. How can I prevent overwriting of files when using scp command under Linux, Mac OS X or Unix like operating systems?

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I have setup a master / local server combination using OpenSSH. My local server depends upon master server for a remote sourcing. The remote sourcing should set a large number of variables locally in a bash shell script. The code is:

user@slave $ source ssh user@master "/service/dyn.master.setenv.sh --mode=slave"
echo “$var”

The var is not setting and I am getting various errors. How can I do a remote "source" of a bash script file (from master.example.com) and set a shell variable locally at slave.example.com?

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How do I reboot my HP Linux server using command line option? How do I remotely reboot my CentOS or Debian based Linux server?

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How do I add my RSA or DSA keyfile in shell script itself for the connection so that I need to carry only one file on my USB pen drive instead of $HOME/.ssh/id_rsa file under Unix / Linux operating systems?

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How do I find out my Dell server service tag using command line under RHEL / Fedora / Red Hat / CentOS / Scientific Linux operating systems?

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I‘ve a remote Unix server running with OpenSSH remote login service. The openssh is configured for passwordless login using ssh keys. Our ISP allows to boot all Linux servers into the rescue mode. It allow us to bring a server online remotely in order to troubleshoot system problems that would normally only be resolved by an OS Reload (such as accidentally deleting files or wrong firewall configurations blocking ssh access). When server boots into a remote rescue mode I can connect using SSH. They SSH keys will not be the same in the rescue mode so I get key mismatch messages as SSH keys are re-generated on each boot:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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 the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
e1:9b:5c:16:a6:cd:11:10:3a:cd:1b:a2:16:cd:e5:1c.
Please contact your system administrator.
Add correct host key in /home/user/.ssh/known_hosts to get rid of this message.
Offending key in /home/user/.ssh/known_hosts:1
RSA host key for www.cyberciti.biz has changed and you have requested strict checking.
Host key verification failed.

How do I ignore OpenSSH hos key checking from my Apple OS X laptop while login using the ssh?

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How do I find out my RHEL (Red Hat Enterprise Linux) 6 Linux kernel version number running on HP server?

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