≡ Menu

yum command

Red Hat Enterprise Linux 5 IMPORTANT Security Update [ 4-Nov-2008 ]

Red Hat today released kernel updates to fix at least 15 security flaws in its core called Linux kernel. RHEL users can grab the latest updates from RHN website or by simply running yum update command. This update has been rated as having important security impact.
[click to continue…]

Red Hat / CentOS Linux 5.x: Perl Performance Bug Fix Available

Perl version supplied with RHEL has bug, which will result code running at least 100 times slower than expected speed. Now, Red Hat updated perl packages that fix a performance issue. Earlier only solution was installing your own perl under /usr/local or other location. This fix will now take care of performance penalty.

Perl is a high-level programming language commonly used for system administration utilities and Web programming.

These updated packages fix a large performance degradation. This issue was most noticeable when using "bless" and "overload" combinations, as well as when using the Perl DBI modules.

Users of perl are advised to upgrade to these updated packages, which resolve this issue.

How do I update perl under RHEL / CentOS Linux?

Type the following command
# yum update

CentOS / Red Hat Enterprise Linux 5.2 Poor NFS Performance and Solution

A few days ago I noticed that NFS performance between a web server node and NFS server went down by 50%. NFS was optimized and the only thing was updated Red Hat kernel v5.2. I also noticed same trend on CentOS 5.2 64 bit edition.

NFS server crashed each and every time web server node tried to store a large file 20-100 MB each. Read performance was fine but write performance went to hell. Finally, I had to rollback the updates. Recently, while reading Red Hat site I came across the solution.

Updated kernel packages that fix various security issues and several bugs are now available for Red Hat Enterprise Linux 5:

* a 50-75% drop in NFS server rewrite performance, compared to Red Hat
Enterprise Linux 4.6, has been resolved.

After upgrading kernel on both server and client my issue resolved:
# yum update

shoes – A cross-platform Windowing Applikit

Shoes is a very informal graphics and windowing toolkit. It's for making regular old apps that run on Windows, Mac OS X and Linux. It's a blend of my favorite things from the Web, some Ruby style, and a sprinkling of cross-platform widgets. Shoes uses Ruby as its interface language.

It borrows a few things I like from the web:
=> Hyperlinks and URLs within Shoes and to the web.
=> Simple text layout -- though Shoes eschews floats.
=> Images and colors in the layout and in the background.
=> Margin and padding.
=> Resizable layouts.

How do I install shoes ?

First, get source code, enter:
$ cd /tmp
$ wget http://shoooes.net/dist/shoes-0.r925.tar.gz

Untar it:
$ tar -zxvf shoes-0.r925.tar.gz
$ cd shoes-0.r925
Now install required stuff under Debian / Ubuntu Linux:
$ sudo apt-get install libcairo2-dev libpixman-1-dev libpango1.0-dev libungif4-dev libjpeg62-dev libgtk2.0-dev vlc libvlc0-dev libsqlite3-dev libcurl4-openssl-dev ruby1.8-dev rake
If you are using RHEL / CentOS / Fedora Linux, enter:
# yum install giflib-devel cairo-devel libpixman-devel pango-devel libjpeg-devel gtk2-devel sqlite-devel vlc-devel libcurl-devel ruby-devel
Install it:
$ make
$ sudo make install

Sample output:

build options: shoes raisins (0.r925) [i486-linux]
CC       = cc
RUBY     = /usr
installing executable file to /usr/local/bin
installing libraries to /usr/local/lib/shoes

See READM for for more information.

Hello World application

Sample hello.rb

Shoes.app {
  para strong("Hello, "), " world!"


Shoes.app (:width => 200, :height => 50, :title => "Hi, Guest!") {
   para strong("Hello, "), " world!"
   @buttonQuit = button "Exit"
   @buttonQuit.click { exit() }

Run it as follows:
$ /usr/local/bin/shoes hello.rb
Another example:

Shoes.app {
  name = ask("Please, enter your name:")
  para "Hello, ", name

You can include images from web or create a simple links / urls:

Shoes.app (:title => "My App" ) {
  image "http://theos.in/wp-content/uploads/2008/06/honda-fcx-clarity-car-photo.jpg"
  para( link("Info").click{ alert ("The FCX Clarity, which runs on hydrogen and electricity, emits only water and none of the noxious fumes believed to induce global warming.") })
  para( link("Exit").click{ exit() } )

Sample output:

Loading images from the web

Fig.01: Loading images from the web

Sample applications

You can find sample application in /tmp/shoes-0.r925/samples/ directory. Here is animated clock program:

# Shoes Clock by Thomas Bell
# posted to the Shoes mailing list on 04 Dec 2007
Shoes.app :height => 260, :width => 250 do
  @radius, @centerx, @centery = 90, 126, 140
  animate(8) do
    @time = Time.now
    clear do
      stack do
        background black
        para @time.strftime("%a"),
          span(@time.strftime(" %b %d, %Y "), :stroke => "#ccc"),
          strong(@time.strftime("%I:%M"), :stroke => white),
          @time.strftime(".%S"), :align => "center", :stroke => "#666",
            :margin => 4
      clock_hand @time.sec + (@time.usec * 0.000001),2,30,red
      clock_hand @time.min + (@time.sec / 60.0),5
      clock_hand @time.hour + (@time.min / 60.0),8,6
  def draw_background
    background rgb(230, 240, 200)
    fill white
    stroke black
    strokewidth 4
    oval @centerx - 102, @centery - 102, 204, 204
    fill black
    oval @centerx - 5, @centery - 5, 10, 10
    stroke black
    strokewidth 1
    line(@centerx, @centery - 102, @centerx, @centery - 95)
    line(@centerx - 102, @centery, @centerx - 95, @centery)
    line(@centerx + 95, @centery, @centerx + 102, @centery)
    line(@centerx, @centery + 95, @centerx, @centery + 102)
  def clock_hand(time, sw, unit=30, color=black)
    radius_local = unit == 30 ? @radius : @radius - 15
    _x = radius_local * Math.sin( time * Math::PI / unit )
    _y = radius_local * Math.cos( time * Math::PI / unit )
    stroke color
    strokewidth sw
    line(@centerx, @centery, @centerx + _x, @centery - _y)
Fig. 02: Animated clock

Fig. 02: Animated clock

Shoes manual

The manual can be launched by typing the following command
$ shoes -m

Further readings:

dnsmasq Dns Cache Software Security Update To Fix DNS Spoofing Attacks

Red Hat has shipped a new version of its dnsmasq caching software to plug source UDP port bug. This could have made DNS spoofing attacks (CVE-2008-1447) easier. Dnsmasq is lightweight ultra fast dns cache server forwarder and DHCP server. It is designed to provide DNS and, optionally, DHCP, to a small network.

This update has been rated as having moderate security impact, to upgrade your software, type the following command:
# yum update

This software only available under RHEL 5 / CentOS Linux 5.x. If you are using Debian / Ubuntu Linux, enter:
# apt-get update
# apt-get upgrade

RHEL5: Linux Kernel kexec-tools bug fix update

An updated kexec-tools package that fixes a bug is now available for RHEL systems. The kexec-tools package provides tools that facilitate a new kernel to boot using the Linux kernel kexec feature, either on a normal or a panic reboot. Users of kexec-tools are advised to upgrade to this updated package, which resolves the following issue:

bt: unwind: failed to locate return link
makedumpfile corrupts vmcore on ia64: crash's bt fails to unwind

How do I fix this issue?

Type the following command as root user:
# yum update

How To Upgrade CentOS Linux To Version 5.2

CentOS Linux 5.2 has been released and available for immediate update via yum command or
the i386 and x86_64 Architectures. From the announcement page:

CentOS-5.2 is based on the upstream release EL 5.2.0, and includes packages from all variants including Server and Client. All upstream repositories have been combined into one, to make it easier for end users to work with. And the option to further enable external repositories at install time is now available in the installer.

How do I update from CentOS-5.0 and 5.1 to 5.2?

Simply type the following command as root user:
# yum update
# yum upgrade
Sample output:

shadow-utils-4.0.17-13.el 100% |=========================|  50 kB    00:00
---> Package shadow-utils.i386 2:4.0.17-13.el5 set to be updated
---> Downloading header for cups to pack into transaction set.
cups-1.2.4-11.18.el5_2.1. 100% |=========================| 165 kB    00:00
Transaction Summary
Install      8 Package(s)
Update     191 Package(s)
Remove       2 Package(s)
Total download size: 298 M
Is this ok [y/N]: y

Finally, reboot your computer, enter:
# reboot