Use ssh_config To Simplify Your Life
When using multiple systems the indispensable tool is, as we all know, ssh. Using ssh you can login to other (remote) systems and work with them as if you were sitting in front of them. Even if some of your systems exist behind firewalls you can still get to them with ssh, but getting there can end up requiring a number of command line options and the more systems you have the more difficult it gets to remember them. However, you don't have to remember them, at least not more than once: you can just enter them into ssh's config file and be done with it.
For example, let's say that you have two "servers" that you connect to regularly, one at your house that's behind your firewall. Further, let's say that you use dyndns to make your home IP address known, and that you've got ssh listening on port 12022 rather than the default port 22 (and you've got your firewall forwarding that port to the server). So to connect you need to run:
$ ssh -p 12022 example.dyndns.org
The second system, let's say is local and you just connect with:
$ ssh 192.168.1.15
The second one is not too bad to type, but a name would be easier. You could put the name in your /etc/hosts file, or you could set up a local DNS server, but you can also solve this problem using ssh's config file.
To create an ssh config file execute the commands:
$ touch ~/.ssh/config $ chmod 600 ~/.ssh/config
Now use your favorite text editor to edit the file and enter the following into it:
Host server1 HostName example.dyndns.org Port 12022 Host server2 HostName 192.168.1.15
The Host option starts a new "section": all the options that follow apply to that host till a new "Host" option is seen. The "HostName" option specifies the "real" host name that ssh tries to connect to (otherwise the "Host" value is used). The "Port" is obviously the port that ssh tries to connect to, if you don't specify a port, the default port is used.
Now you can connect much more simply:
$ ssh server1 $ ssh server2
These are just a few of the options that you can set in ssh's config file. You can also, for example, specify that X11 forwarding be enabled. You can set up local and remote port forwarding (i.e. ssh's -L and -R command line options, respectively). Take a look at the man page (man ssh_config) for more information on the available options.
One of the added benefits of using ssh's config file is that programs like scp, rsync, and rdiff-backup automatically pick up these options also and work just as you'd expect (hope).
Mitch Frazier is an Associate Editor for Linux Journal.
- Free Today: September Issue of Linux Journal (Retail value: $5.99)
- The Tiny Internet Project, Part I
- Bitcoin on Amazon! Sort of...
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- Android Browser Security--What You Haven't Been Told
- Returning Values from Bash Functions
- Securing the Programmer
- Epiq Solutions' Sidekiq M.2
- Nativ Disc
Pick up any e-commerce web or mobile app today, and you’ll be holding a mashup of interconnected applications and services from a variety of different providers. For instance, when you connect to Amazon’s e-commerce app, cookies, tags and pixels that are monitored by solutions like Exact Target, BazaarVoice, Bing, Shopzilla, Liveramp and Google Tag Manager track every action you take. You’re presented with special offers and coupons based on your viewing and buying patterns. If you find something you want for your birthday, a third party manages your wish list, which you can share through multiple social- media outlets or email to a friend. When you select something to buy, you find yourself presented with similar items as kind suggestions. And when you finally check out, you’re offered the ability to pay with promo codes, gifts cards, PayPal or a variety of credit cards.Get the Guide