Phil's answer is a very good one; I'd like to expand on it a bit.
When you log in to a server via SSH, you have command-line access to
it, meaning that in essence you are sitting in front of it running the
equivalent of Terminal on the Mac or Run on Windows (I think that's
right). Many things that I normally do using SSH can be done via
WebDAV or even in an FTP client, in particular copying, moving,
renaming, deleting and changing the permissions or owners of files. I
would feel hampered, however, by the inability to execute shell
scripts directly (they could be executed indirectly using Rev shell
scripting in a web page thoug) and to use the full panoply of unix
commands to manage my site(s). The speed of operations is also
usually much greater, since very little communication is involved and
repetitive actions, like deleting a directory full of sub-directories,
are virtually instantaneous.
That power comes with considerable risk, however, and the risk greatly
increases when you are able to assume, temporarily or permanently, the
power of the 'root' user, who can do ANYTHING. (To become the 'root'
user temporarily, one prefaces commands with 'sudo', meaning Switch
User to DO as root, more or less.) I have that power on my own Macbook
Pro machine, and I'm accustomed to it. But I can certainly understand
when a host decides to limit root access, use of sudo, or even SSH: it
greatly decreases the possibility that one user's mistake -- or
malevolence -- will bring about disaster.
Some hosts, such as the one I use, offer virtual hosting environments,
where the user's space is segregated by some clever programming from
everyone else's, so the user is in effect using a completely separate
server. In those environments, root access or limited sudo use can be
provided, with the caveat that the user had better be knowledgeable
and careful if she wants to keep from destroying everything. (As an
example, a root user typing "rm -rf /" on the command line and
pressing return will delete the entire operating system and all
data.) An even greater power comes with the leasing of an actual
server computer maintained by the host: in this situation, you have
the same power you would have if the server was located in your
basement. So, if you need more power and access, there are ways to
get it, but you and the host have to assume substantial additional
responsibility and risk. For many and probably most website owners/
developers, a more limited environment such as On-Revs is perfectly
adequate.
I hope this makes my interest in SSH and root/sudo more clear!
George
On Apr 21, 2009, at 1:16 AM, Phil Davis wrote:
Colin Holgate wrote:
What does SSH give you that you don't get with the secure disk image
access?
Hi Colin,
I assume when you say "secure disk image access" you're talking about
WebDAV, which is what on-rev offers.
In a nutshell:
- SSH gives you the ability to execute any line command known to the
server. You have a user account on the server and can log into it and
do whatever you know how to do via the command line, including the
setting of server properties, the running of scripts, etc.
- WebDAV lets you mount a server-side folder on your computer as
though it were an external HD, and you can use it like one (except
upload/download speeds are are subject to your internet connection
speed, unlike an external HD!). So WebDAV's functionality is limited
to file services, but you have a GUI for it.
I wish on-rev had SSH. However, its absence is partially compensated
for by the power of Rev code in irev pages, if indeed the server
version of Rev will give us abilities like those of the desktop
versions to sense and control similar kinds of things.
--
Phil Davis
PDS Labs
Professional Software Development
http://pdslabs.net
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