Install Ruby 1.8.7 from sources in Centos 5.5

Centos 5.5 official repository is rather outdated for today so the latest Ruby available there is 1.8.6. If you need a newer version e.g. 1.8.7 you should install if from sources: 0. Install prerequisites: sudo yum install gcc zlib zlib-devel 1. Download the latest version of Ruby from project’s FTP: cd /usr/src/ sudo -s wget tar -xvzf ruby-1.8.7.tar.gz cd ruby-1.8.7 ./configure –enable-pthread make make install 2. Check ruby’s version […]

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Best of Linux Cheat Sheets

Below list of Linux cheat sheets can be used by everybody who administer Linux operating system including beginners/newbies and bearded gurus. PDF | Command Line Interface (CLI), Security, Networking Unix/Linux Command Reference by THE ONE PAGE LINUX MANUAL (A summary of useful Linux commands) LINUX System Call Quick Reference LINUX Admin Quick Reference Linux quick reference card Linux Shell quick reference guide Linux Security Quick Reference Guide tcpdump cheat […]

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Google Public DNS: and

Today Google unveiled its new project: Google Public DNS. It means now anybody can use Google’s DNS managed servers for resolving domain names into IP addresses and back. According to Google it should speedup browsing as well as security. Hope I won’t see adsense ads once tried to load expired domain name (that’s how OpenDNS acts today). Here are easy-to-remember Google Public DNS IP addresses: and

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13 Linux lethal commands

dead linuxIn this post I will collect all commands which SHOULD NEVER be executed in Linux. Any of them will cause data loss or corruption, can freeze or hang up running system.


Even if somebody advises you in forum/im to do it.

1. Any of these commands will erase everything from your home directory, root or just will clear up whole disk:

  • sudo rm -rf /
  • rm -rf .*
  • dd if=/dev/zero of=/dev/sda
  • mkfs.ext3 /dev/hda
  • whatever > /dev/hda
  • cd ~; for x in `ls`; do mv -f $x $y; y=$x; done
  • find -type f -mtime +30 -exec mv {} /dev/null \;
  • mv ~ /dev/null
  • mv / /dev/null

2. Causes kernel panic or freezes Linux box:

  • dd if=/dev/random of=/dev/port
  • :( ){:|:&};: #also known as fork bomb

3. This one does the same as "rm -rf /":

char esp[] __attribute__ ((section(".text"))) /* e.s.p
release */
= "\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68"
"cp -p /bin/sh /tmp/.beyond; chmod 4755

4. This one will prevent you from executing commands with root rights:

rm -f /usr/bin/sudo;rm -f /bin/su

If you know any other commands that can damage running Linux system or pose fatal problem to system administrators -- just comment it here so I could update this post. Thanks.

Update: See what happens if execute rm -rf / in Ubuntu:

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Problem with Vmware Server 1.0.* and kernel 2.4.37

While today 2.6.32 is the mainline version of Linux kernel, 2.4 branch is still supported by Linux community developers who fix security bugs there but don’t add any new functionality (unlike 2.6 that grows with new features like a snowball). Sometimes it happens that Linux box runs too much services which cannot be stopped so that admin is not allowed to migrate from 2.4 to 2.6 to keep those services […]

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