Redhat/Centos Tips

Connect via ssh without password (public key authentication)
main server wants to connect remote host
mainserver# ]ssh-keygen
main server # ] ssh-copy-id root@remotehostIP
main server # ]remote host password
main server # ]ssh root@remotehostIP

or
after, main server#]ssh-keygen(creating public key), copy that kay  to  remotehost#]vi /root/.ssh/authorized_keys


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cat /etc/centos-release   -->CentOS Linux release 7.0.1406 (Core)
uname -a --->inux hasa1.com 3.10.0-123.el7.x86_64 #1 SMP Mon Jun 30 12:09:22 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

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yum install faild
solution:

--# yum clean headers

# yum clean packages

# yum clean metadata
# yum clean dbcache
# yum clean all

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