Last updated: 05/17/2005
Linux is an open source operating system, meaning that it does not come from a vendor. It is, instead, developed and supported by thousands of programmers around the world. It is freely available to anyone. While originally developed for the Intel/PC platform, it has been ported to a wide variety of hardware. For these reasons, it is becoming increasingly popular. It is conceivable that it may be running on some of SCD's supercomputers in the fairly near future. Because of that, SCD wants to give our users access to Linux so that they can gain experience with it. This is the purpose of the longs system.
In addition, having this system will also give the SCD systems staff a chance to gain experience with Linux from the support side. We have introduced a few Linux workstations in SCD, and many of our staff have mostly positive experiences with Linux on home systems, but longs is our first user-accessible server running Linux. Also, the support paradigm for Linux is very different than anything SCD is used to. There is no vendor we can contact if software problems come up. Instead, we report bugs to the individual developer of a particular software package, or we access the widely available Linux resources on the Internet to find fixes for software problems. In practice this has worked quite well for many sites (including some here at UCAR) that have gone heavily into Linux, but it remains to be seen how well this will work in SCD's environment.
Important note: Users may experience problems because Linux uses a slightly different search path than does Solaris. This means that users who are sharing a home directory between longs and meeker and who reset their search path in their "dotfiles" may have problems finding system commands on longs. It is okay to add directories to the search path even if they do not exist on one or the other system, but do not replace the default search directories provided by the system. Example for csh users:Incorrect:
set path=(/dir1 /dir2)Correct:
set path=($path /dir1 /dir2)
cat /etc/motd
to see recent system news. We will also announce major changes, as we
do for all our systems, in the
SCD Daily Bulletin.
Longs is the first general user access system to use SCD's centralized authentication server database. This is the same password database that is used by the UCAR Central Authentication Services (UCAS) systems for authenticating users to access internal web pages from outside UCAR, for authenticating users to access the web page development system, and for the UCAR online timecard system.
Keep in mind that if you change your password on longs, you will also change your password for anything else that uses the authentication server database. Similarly, if you change your UCAS password, this will also change your password on longs.
Because this password is used by the timecard system, all UCAR employees should already have passwords in the authentication server. However, if you are not a UCAR employee and have never registered to use our UCAS system, you may have to obtain a UCAR account first. Setting up a UCAR account gives you access to the UCAS system and also creates a password for you in the authentication server database which would enable you to access longs. To request a UCAR account if you are associated with an NCAR division or UCAR program, contact the system administrators for that division or program. If you are a new user and would like to request an account on longs, or for university users who need UCAS accounts, please contact the SCD Customer Support Help Desk at 303-497-1278.
One consequence of a shared home directory is that your "dotfiles" (.cshrc, .profile, or .login) will be executed on longs. Since Linux stores program executables in different directories than does the Solaris system on meeker, some system commands may not work if your search paths are not set correctly. Review the note at the beginning of this document for more information.
As usual, the /ptmp file system is not backed up, and the system administrators may have to manually scrub files from /ptmp if it becomes full, so that all users have temp space available. Therefore, you should not store anything on /ptmp that cannot be easily recreated. Longs does provide direct access to the Mass Storage System (see the System software section below). Users with local home directories have a quota of approximately 50MB there. This area is not that large and is not intended for long-term storage of data. Users with remote home directories have whatever quota is already assigned there.
rpm -q -a
will print a list of the packages installed on the system. Type
man rpm for more information on the RPM system.
There are many packages installed on the system already. There are many more that are available around the Internet that have not been installed. If your favorite application from meeker is missing, notify the SCD Consulting Office (303-497-1278) and they will work to locate the appropriate Linux application and have it installed.
We expect that you will find most of the applications you are accustomed to using on a Unix system available on Linux too. Many common tools that use the same X Window System that Unix workstations use are available, such as the netscape or mozilla (display-oriented) web browsers, and a variety of email access tools, including both IMAP and POP servers, so that longs can serve as your mailbox system if you want.
Longs also has a full interface to SCD's Mass Storage System (MSS). All of the usual DCS commands are available (msls and friends), as well as the msrcp command for transferring data files to and from the MSS. Unfortunately, there is no HiPPI driver yet available for Linux, so longs does not have msread/mswrite.
We have installed the NCAR Graphics package.
Linux also comes with the usual array of shells and interpreted languages. The standard Linux shell is bash, the "Bourne Again SHell", which is the old Bourne shell with some of the nicer features of the C Shell merged in. The standard and extended versions of the C Shell (csh and tcsh) are also available.
The most popular interpreted language is the Practical Extraction and Report Language (perl). This language is used quite a bit on Unix and Linux systems and is well supported for Linux. In addition, a relatively new object-oriented language called Python was first developed for Linux and is therefore likely to be well supported.
One application that is not available for Linux is the Network Queueing
Envirnment, or NQE. This is the qsub command that some meeker users use
to submit jobs to the supercomputers. The qsub command is not available
for Linux.
Important note:
The correct paths to all compilers and system commands on longs are
provided by default. These paths differ from those on meeker, which
runs the Solaris operating system. So if you share a home directory
between longs and meeker, you need to set paths using the
$path system variable as explained in the
note at the beginning of this document.
In addition to the default system compilers, SCD has installed the Portland Group Inc. (PGI) compilers which have a very good reputation. These include pgf90 (Fortran90), pgf77 (Fortran77), and C and C++ compilers. Manuals for the PGI compilers are provided on SCD's website.
Please note that the PGI compilers are a licensed product. The licenses that
SCD currently has will permit two users to use the compilers simultaneously.
If you frequently find that you are unable to get a license, please report this
to the Consulting Office. If we have lots of conflicts, we may consider
purchasing more licenses.
If you have questions about this document, please contact SCD Customer Support. You can also reach us by telephone 24 hours a day, seven days a week at 303-497-1278. Additional contact methods: consult1@ucar.edu and during business hours in NCAR Mesa Lab Suite 39.
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