CentOS 7 - yum install not working

These steps might help you,

1. yum clean all & yum clean metadata

2. Check the files in /etc/yum.repos.d and make sure that they don't all have enabled = 0 for each repo (there may be more than one per file).

3. Finally you would be able to do yum update and search for desired packages.

For CentOS/RHEL 7, autossh is no longer available in Repoforge repository. So you will need to build and compile it from the source, here is what you should do:

$ sudo yum install wget gcc make
$ wget http://www.harding.motd.ca/autossh/autossh-1.4e.tgz
$ tar -xf autossh-1.4e.tgz
$ cd autossh-1.4e
$ ./configure
$ make
$ sudo make install