The Best Multiplatform Development Environment that Ever Lived on One Box
There are two versions of the SSH protocol: 1 and 2. I am using version 2 of the protocol (sometimes simply called SSH2). SSH (secure shell) gives me three advantages from a security standpoint:
High degree of authentication security using public key authentication
High degree of transmission security by encrypting all traffic after authentication
Encrypted TCP tunneling for connection to services not available to the public (often referred to as VPN or virtual private networking)
Public key authentication works through the use of a public key and a private key. A key in this context is a string of characters used to identify an individual. Keys can be a variety of lengths. The longer the key, the harder it is to break, but performance in the encryption and decryption process can suffer with longer keys. Usually a tool, such as ssh-keygen, is used to generate key pairs. Information encrypted with the private key can only be decrypted with the public key. Likewise, information encrypted with the public key can only be decrypted with the private key.
Once keys have been generated, they can be used in secure connections with SSH. The private key (as its name implies) should be kept secure at all times. Often it is kept on a floppy disk or other removable media when other people may have access to a machine you also use (I keep mine on a Java powered ibutton, but that is another story). The public key, however, may be distributed, well, publicly. A copy of the public key must be present on the remote server that you wish to connect to using SSH.
When you attempt to make a connection with SSH, a small bit of information is encrypted using your public key on the server. This information is called the session key. The SSH server on the remote machine sends the encrypted session key back to the client. The client then attempts to decrypt this bit of information using your private key. This information (once successfully decrypted) is then used to encrypt the rest of the session. This solution is simple and elegant. The information used later on to encrypt the rest of the session is never passed in cleartext over the insecure Internet.
One of the most powerful features of SSH is the ability to use TCP tunnels. There are two types of tunnels: local and remote. With a local tunnel, you specify a port for your local machine to listen on, as well as a remote machine and port on the other side of your SSH connection to connect to. Once a local tunnel is established, you can connect to the specified port on your local machine, and it will be as if you had connected to the remote machine on the port you specified for the tunnel. With remote tunnels, you specify a port for the remote machine to listen on and a local address and port to connect to. When a connection is made to the specified port on the remote machine, it will be as if the connection had been made to the local machine and port you specified for the tunnel. The way these connections work is not always understood, so let's take two examples from my own configuration file:
LocalForward "5521:localhost:1521" RemoteForward "6010:localhost:6000"
On the Linux box I run a database server. I want to be able to use the client tools remotely, but in a secure way. The listener service is bound to port 1521. In the first example above, the first parameter (5521) is the port that my local machine will listen on. The second and third parameters refer to the remote machine. So, localhost in this case is the remote machine's localhost. After establishing my secure shell session, the tunnels are automatically created from the configuration file. I can then point the client tools to my local machine at port 5521. All traffic generated by the client tools will transparently be forwarded over the secure tunnel to the remote machine.
The second example uses the X Window System over a secure tunnel. Without getting into too much detail, X is somewhat counter-intuitive; you run an X server on your local machine, and X clients are run on the remote machine. These clients connect to the X server. X has a notion of display numbers bound to ports. Display 0 uses port 6000, display 1 uses 6001 and so on. In the second example above, the first parameter (6010) refers to the port on the remote machine. In this case, I am using display 10, bound to port 6010, to run my X clients. The second and third parameters refer to my local machine. So, localhost in this case is my machine's localhost. On the remote machine, I might run a command like:
xterm -display localhost:10&
This will cause xterm to connect to port 6010, which will transparently connect through the secure tunnel to my machine on port 6000 (the default port for the X server).
In actuality, SSH supports automatically tunneling X clients.
Since the tunnel is established through an already secure connection, all information passing along the tunnel is encrypted. The upside is a high degree of security over a public and insecure network. The downside is overhead in encrypting everything on the fly.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- Doing for User Space What We Did for Kernel Space
- SuperTuxKart 0.9.2 Released
- Google's SwiftShader Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide