If you have software packages which you wish to share with others or simply between your own personal machines, a neat and easy solution is to create your own YUM repository and provide your .repo file for download.
YUM is by far the easiest method of installing software on Red hat, Centos and Fedora. Not only does it mean you don't need to trawl the web looking for somewhere to download the packages, YUM does a great job of satisfying any package dependencies. As long as the required packages are available in the enabled repositories on your system, YUM will go out and get everything you need.
To create your own YUM repository, you will need to install the yum-utils and createrepo packages:
yum install yum-utils createrepo
yum-utils contains the tools you will need to manage your soon to be created repository, and createrepo is used to create the xml based rpm metadata you will require for your repository.
Once you have installed these required tools, create a directory in your chosen web server's document root e.g:
mkdir -p /var/www/html/repo/recital/updates
Copy the rpm's you wish to host into this newly created directory.
The next step is to create the xml based rpm metadata. To create this use the createrepo program we installed earlier.
At the shell type the following command:
createrepo -v -s md5 /var/www/html/repo/recital/updates
This will create the required metadata in the repodata directory of your /var/www/html/repo/recital/updates directory.
root@test repodata]# ls -l rwotal 44 -rw-r--r-- 1 root root 28996 Jan 13 21:42 filelists.xml.gz -rw-r--r-- 1 root root 284 Jan 13 21:42 other.xml.gz -rw-r--r-- 1 root root 1082 Jan 13 21:42 primary.xml.gz -rw-r--r-- 1 root root 951 Jan 13 21:42 repomd.xml
To do a final consistency check on your repository run the following command:
verifytree /var/www/html/repo/recital/updates
We now have a fully functioning YUM repository for our hosted rpm packages.
The next process is to create a .repo file in the client systems /etc/yum.repos.d directory.
Navigate to the /etc/yum.repos.d directory on your system as root.
Using your preferred text editor to create the .repo file. In this example I will call it recital.repo.
Now paste in the following lines:
[Recital] name=Recital Update Server baseurl=http://ftp.recitalsoftware.com/repo/recital/updates enabled=1 gpgcheck=1
Once that is saved, at the shell prompt on the same machine (YUM client system).
$ yum repolist Loaded plugins: presto, refresh-packagekit repo id repo name status Recital Recital Update Server enabled: 1 adobe-linux-i386 Adobe Systems Incorporated enabled: 17 fedora Fedora 12 - i386 enabled: 15,366
As you can see the Recital repo is now being picked up and we have access to all the packages it is hosting.
See how easy that was!
Here's how to set up field validation based on dynamic values from another table.
Using the products.dbf table from the southwind sample database, validation can be added to the categoryid field to ensure it matches an existing categoryid from the categories.dbf table.
open database southwindThe rlookup() function checks whether an expression exists in the index (master or specified) of the specified table . An attempt to update categoryid with a value not in the list will give an error: Validation on field 'CATEGORYID' failed.
alter table products add constraint;
(categoryid set check rlookup(products.categoryid,categories))
If you have access to the Recital Workbench, you can use the modify structure worksurface to add and alter your dictionary entries, including a customized error message if required.
If you are running your Redhat/Centos or Fedora machine in an enterprise environment you may be sitting behind a network proxy server like squid.
If you try and update or install software it will fail with timeouts or errors contacting the repository mirrors.
To configure YUM to work with your proxy server you need to add the following line to your /etc/yum.conf file.
Anonymous proxy configuration:
proxy=http://yourproxyip:port/
If your proxy server requires authentication add the following lines to your /etc/yum.conf file instead.
proxy=http://yourproxyip:port/ proxy_username=youruser proxy_password=yourpassword
You will be able to update and install software now, give it a go!
FOREACH array_expression AS value
statements...
ENDFOR
FOREACH array_expression AS key => value
statements...
ENDFOR
The first form loops over the array given by array_expression. On each loop, the value of the current element is assigned to value and the internal array pointer is advanced by one (so on the next loop, you'll be looking at the next element). The second form does the same thing, except that the current element's key will be assigned to the variable key on each loop. This form works only on associative arrays and objects.
Recital provides the following additional benefits:
- Easy to Install and Deploy - Users can set up Recital in minutes enabling organizations to deliver new applications faster than other databases.
- Easy to Administer - Recital is a low administration database that eliminates the need for highly trained, skilled, and costly database administrators to maintain the database.
- High Performance - Superior database performance for the most demanding of OLTP applications. Additionally, Clustered Recital provides 99.999% availability.
- Embeddable Library - Recital Embedded Edition provides in-process data storage engine that delivers all the features of a traditional relational database but in a size which makes it ideally suited for ISVs/VARs who need a small footprint and easy to use toolkit.
- Platform Independence - Recital runs on Linux, Solaris, AIX, HP-UX, Windows, and Mac OS X giving organizations complete flexibility in delivering a solution on the platform of their choice.
// declare an empty dynamic array
a = array()
// declare a simple dynamic array
a = array("barry", "recital", "boston")
foreach a as value
echo value
endfor
// declare an associative array
a = array("name" => "barry", "company" => "recital", "location" => "boston")
echo "length of a is " + len(a)
foreach a as key => value
echo "key=" + key + ", value=" + value
endfor
This is a good primer for getting familiar with using Infiniband with Redhat/Centos Linux.
http://people.redhat.com/dledford/infiniband_get_started.html
Getting Started with InfiniBand
The first step to using a new infiniband based network is to get the right packages installed. These are the infiniband related packages we ship and what they are there for (Note, the Fedora packages have not all been built or pushed to the repos yet, so their mention here is as a "Coming soon" variety, not an already done variety):
It would appear that gigabit LAN is not! In fact it often runs at the same speed as 100Mbps LAN. Let's look at why exactly.
After configuring your network you can use the ifconfig command to see what speeds the LAN is connected. Even though 1000Mbps is reported by the card, the reality is that the overall throughtput may well be ~100Mpbs. You can try copying a large file using scp to demonstrate this.
As it turns out, in order to use a gigabit LAN you need to use CAT6 cables. CAT5 and CAT5E are not good enough. End result, the ethernet cards throttle back the speed to reduce dropped packets and errors.
You can find a good article here titled Squeeze Your Gigabit NIC for Top Performance. After tuning up the TCP parameters i found that it made no dfifference. The principal reasons behind low gigabit ethernet performance can be summed up as follows.
- Need to use CAT6 cables
- Slow Disk speed
- Limitations of the PCI bus which the gigabit ethernet cards use
You can get an idea about the disk speed using the hdparm command:
Display the disk partitions and choose the main linux partition which has the / filesystem.
# fdisk -l
Then get disk cache and disk read statistics:
# hdparm -Tt /dev/sda0
On my desktop system the sata disk perfomance is a limiting factor. These were the results:
/dev/sda1:
Timing cached reads: 9984 MB in 2.00 seconds = 4996.41 MB/sec
Timing buffered disk reads: 84 MB in 3.13 seconds = 58.49 MB/sec
Well, that equates to a raw disk read speed of 58.49 * 8 = 467Mbps which is half the speed of a gigabit LAN.
So.. NAS storage with lots of memory looks to be the way to go... If you use the right cables!