|
|
Last update:
Sat Sep 24 06:47:07 2005
Wed Oct 5 16:30:02 2005
Thu Mar 23 14:01:59 2017
Do we offer File Transfer Protocol (FTP) services?
Yes: the generic hostname ftp.math.utah.edu and its predecessors have provided freely accessible FTP services for more than two decades. We send out thousands of files, and a few tens of gigabytes, every day.
FTP services are available both via remote FTP clients (typically called just ftp, although ncftp is a very much better one), and via Web browsers. ncftp and browsers accept Internet Uniform Resource Locators (URLs) of the form ftp://ftp.math.utah.edu/.
All Unix FTP trees contain a few standard top-level directories, and conventionally, the one called pub is the root of the file resources offered to the public. Thus, you can start at the address ftp://ftp.math.utah.edu/pub, or after connecting with an FTP client, do cd /pub, to get there.
FTP is one of the oldest network protocols, and all networked operating systems have a client program named ftp. Here is how to start a session:
% ftp ftp.math.utah.edu .... Name (ftp.math.utah.edu:nbeebe): ftp 331 Guest login ok, send your complete e-mail address as password. Password: ... ftp>
Some older systems require a username of anonymous instead of ftp. Most modern FTP servers expect the password to look like an e-mail address.
Never use your normal Unix username and password with an FTP client. Few systems today permit such logins, and most FTP servers record logins, including the incoming hostname, username, and password. If you do this by mistake, you should immediately change your password, and never reuse the old one again.
The newer ncftp client handles the anonymous login for you, so you don't need to supply a username and password.
My Web browser cannot access the FTP site. Why?
Some Web browsers supply an unacceptable default username and password for anonymous FTP logins. You might then get a pop-up warning like this: The response '[email protected]' is not valid. It should be possible to change this with the Edit -> Preferences menu path, but it may not be obvious how. With mozilla and netscape, follow that path to Advanced, and select and fill in the box labeled Send this email address as anonymous FTP password.
When Web browsers use the FTP protocol instead of the normal HTTP protocol, they do not expect to find index.html files: instead, they just display directory listings. You can still visit any index.html file that is present in the directory listing, and it will then behave the same as if it were visited over an HTTP connection.
A lot! Our FTP tree held almost 400,000 files in late 2005. There are many software packages, each with a directory immediately underneath the pub directory.
For example, at ftp://ftp.math.utah.edu/pub/date/, you can find current and historical versions of the date package that provides a number of Unix shell scripts for processing calendar dates. Package archives are nearly always available in a number of different formats, including .jar, .tar.gz, .tar.bz2, .zip, and .zoo.
There are two large bibliography archives at pub/bibnet and pub/tex/bib, collectively offering nearly 400,000 BibTeX entries in numerical mathematics, fonts, typography, and broad areas of computer science.
There are mirrors of several important sites under pub/mirrors (URL ftp://ftp.math.utah.edu/pub/mirrors/).
How do I access CTAN (Comprehensive TeX Archive Network)?
Our mirror of the CTAN archive is visible locally under /usr/local/src/ctan, and also via the URLs ftp://ctan.math.utah.edu/pub/ctan/ and http://ctan.math.utah.edu/pub/ctan/.
How do I find a particular file in the archive?
With Web browsers, most of our departmental Web pages show a search box at the bottom that offers buttons for selecting local (default) or global searching. Just type in the filename that you are looking for, and then select the Search button.
With an FTP client, use the indexing command, as in this sample session that finds and retrieves a file:
% ncftp ftp://ftp.math.utah.edu/
...
ncftp / > quote site index bibclean-2.11.4.zip
index bibclean-2.11.4.zip
/pub/bibclean/bibclean-2.11.4.zip
/pub/bibclean/bibclean-2.11.4.zip-lst
/pub/bibclean/bibclean-2.11.4.zip.sig
/pub/tex/bib/bibclean-2.11.4.zip
/pub/tex/bib/bibclean-2.11.4.zip-lst
(end of 'index bibclean-2.11.4.zip')
ncftp / > get /pub/bibclean/bibclean-2.11.4.zip
bibclean-2.11.4.zip: 1.59 MB 2.90 MB/s
ncftp / > quit
How can I upload a file to the FTP archive?
As a matter of policy and security, we do not permit uploading, except by prior arrangement with trusted users, and then only for a brief time interval.
How can I verify correct transfer of files?
The FTP protocol uses the reliable TCP/IP protocol underneath, so file corruption during transfer should always be detected and reported.
However, there is still the possibility that an attacker has broken into our systems, and replaced one or more archive packages with maliciously modified versions. That has happened elsewhere to packages of major importance, and might someday happen to us, even though we try hard to keep our systems secure.
File checksums and digital signatures provide a way to at least detect such intrusions, but it is the responsibility of the remote user to actually verify those checksums and signatures.
All software package directories in the FTP tree contain at least two files, MD5SUM and SHA1SUM, that contain checksums of files in those directories, using the md5sum and sha1sum utilities that produce MD5 (Message Digest version 5) and SHA-1 (Secure Hash Algorithm version 1) checksums.
Effective September 2005, a third checksum file, RIPEMD-160, will be present in newly updated package directories, supplying checksums from the ripemd-160 utility.
Should it ever prove possible to produce a modified archive file with the same checksum as the original file, that checksum will be useless. However, it is believed to be entirely infeasible for this to happen to multiple checksum algorithms, which is why we provide at least two for independent verification.
In addition, the authenticity of the checksum files can be verified by instead fetching their companions with digital signatures: MD5SUM.asc, RIPEMD-160.asc, and SHA1SUM.asc. Binary distribution files usually have small detached-signature files with extension .sig. You can then use the Pretty Good Privacy program, pgp, or the Gnu Privacy Guard program, gpg, to verify the digital signatures and ensure that the reported checksums have not been tampered with.
Since checksums and digital signatures are unfamiliar to many people, there is a tutorial available here.
Is the FTP file tree visible to local users as an ordinary filesystem?
Yes: the root of the FTP file tree is at the local filepath /u/ftp/. Local users can freely examine, and possibly copy, any files under the public tree /u/ftp/pub/.
Can I have my own directory in the local FTP tree?
Faculty, staff, and graduate students with an exceptionally strong need for this service can be given such access by systems staff. The local directory path will then be /u/ftp/u/ma/username, and the remote URLs will be ftp://ftp.math.utah.edu/u/ma/username and http://www.math.utah.edu/u/ma/username.