2 - Raspberry PI Community Projects

$ scp file machine:/tmp/
sftp is an interactive command, similar to ftp. In a single session, sftp can transfer several
files, and it is possible to manipulate remote files with it (delete, rename, change permissions,
etc.).
Debian uses OpenSSH, a free version of SSH maintained by the OpenBSD project (a free operating
system based on the BSD kernel, focused on security) and fork of the original SSH software
developed by the SSH Communications Security Corp company, of Finland. This company initially
developed SSH as free software, but eventually decided to continue its development under
a proprietary license. The OpenBSD project then created OpenSSH to maintain a free version of
SSH.
BACK TO BASICS
Fork
A “fork”, in the soware field, means a new project that starts as a clone of an
existing project, and that will compete with it. From there on, both soware
will usually quickly diverge in terms of new developments. A fork is oen the
result of disagreements within the development team.
The option to fork a project is a direct result of the very nature of free soware;
a fork is a healthy event when it enables the continuation of a project
as free soware (for example in case of license changes). A fork arising from
technical or personal disagreements is oen a waste of human resources; another
resolution would be preferable. Mergers of two projects that previously
went through a prior fork are not unheard of.
Since Etch, OpenSSH is split into two packages. The client part is in the openssh-client package,
and the server is in the openssh-server package. The ssh meta-package depends on both parts
and facilitates installation of both (apt-get install ssh).
GOING FURTHER
Hardware acceleration for
SSH
Some hardware provides native support of mathematical functions used by
encryption, which can speed up the required calculations, thus increasing performance
of some tools (and lightening the load on the main processor). These
tools notably include the OpenSSL library, which is in turn used by OpenSSH.
Although a project for standardization of drivers is underway (notably at the
kernel level), the variety of hardware is still managed inequitably and heterogeneously.
For example, the Padlock system included in Via C3 processors is
only partially supported. While the Linux kernel does offer various encryption
algorithms, the OpenSSL 0.9.8 library in Squeeze only handles delegation of
AES encryption to the hardware dedicated to that purpose, but not the SHA
algorithms; you have to recompile it with a patch.
➨ http://www.logix.cz/michal/devel/padlock/
9.2.2.1. Key-Based Authentication
Each time someone logs in over SSH, the remote server asks for a password to authenticate
the user. This can be problematic if you want to automate a connection, or if you use a tool
190 The Debian Administrator's Handbook