by Jeff Hunter, Sr. Database Administrator
Read more…
by Jeff Hunter, Sr. Database Administrator
by Jeff Hunter, Sr. Database Administrator
This article is a comprehensive guide for installing Oracle Database 10g Release 2 on the Red Hat Enterprise Linux 5 (RHEL5) operating environment.
This is a step by step guide, which will walk you through the installation of Oracle 11g Release 2 on RHEL 5.5 (Red Hat Enterprise Linux 5.5) 32-bit architecture. Oracle 11g Release 2 is supported on RHEL 5 Update 4 or later.
1. Introduction
For those of you who have been using SSH for a while, you will probably understand it’s advantages over the previous telnet style applications such as telnet and remote shell. Although SSH with keys has always been there, not many people know what it is about, and how you can utilize it’s strenghts to make your life as a system administrator a bit more easy.
Getting Started
- First, install OpenSSH on two UNIX machines, hurly and burly. This works best using DSA keys and SSH2 by default as far as I can tell. All the other HOWTOs I’ve seen seem to deal with RSA keys and SSH1, and the instructions not surprisingly fail to work with SSH2.
- On each machine type ssh somemachine.example.com and make a connection with your regular password. This will create a .ssh dir in your home directory with the proper perms.
- On your primary machine where you want your secret keys to live (let’s say hurly), type
- ssh-keygen -t dsa
This will prompt you for a secret passphrase. If this is your primary identity key, make sure to use a good passphrase. If this works right you will get two files called id_dsa and id_dsa.pub in your .ssh dir. Note: it is possible to just press the enter key when prompted for a passphrase, which will make a key with no passphrase. This is a Bad Idea ™ for an identity key, so don’t do it! See below for uses of keys without passphrases.
The following sections hope to provide enough information to setup a user new to ssh with the appropriate files necessary for accessing remote hosts in a secure manner. Improvements to and comments about this document are welcome.
Updated: The examples now show ssh version 2 commands, using OpenSSH. There are several security vulnerabilities in protocol version 1. Everyone should have already migrated to version 2 by now, so it was about time for me to also reflect best practises in this document. I also updated the link section at the end of the document to better reflect today’s software selection.
Linux is an outstanding operating system for serving up applications. And there are a ton of possibilities. From content management systems to Web portal creation tools, Linux has just about everything you need. Among those thousands of tools, a select few stand out as the best of the best. Listed below you will find my top 10 must-haves for Linux server/Web/cloud-based tools.
To take advantage of the excellent Linux development environment, you need to have the right tools. Here’s a rundown of some of the best ones out there and the features they have to offer.
Linux is a great development environment. But without sound development tools, that environment won’t do you any good. Fortunately, plenty of Linux and/or open source development tools are available. If you’re a new user you might not know which tools are there, but worry not. Here are 10 outstanding tools that will help you take your development to another level.
Short history of the UNIX operating system
Linux is an implementation of the UNIX operating system concept. UNIX was derived from AT&T’s “Sys V” (System 5). The initialization process is meant to control the starting and ending of services and/or daemons in a system, and permits different start-up configurations on different execution levels (“run levels”).
Some Linux distribution, like SlackWare, use the BSD init system, developed at the University of California, Berkeley.
Sys V uses a much more complex set of command files and directives to determine which services are available at different levels of execution, than the BSD’s do.
Booting the Linux operating system
The first thing a computer does on start-up is a primer test (POST – Power On Self Test). This way several devices are tested, including the processor, memory, graphics card and the keyboard. Here is tested the boot medium (hard disk, floppy unit, CD-ROMs). After POST, the loader from a ROM loads the boot sector, which in turn loads the operating system from the active partition.
The boot blocks is always at the same place: track 0, cylinder 0, head 0 of the device from which we’re booting. This block contains a program called loader, which in Linux’s case is LiLo (Linux Loader), or Grub (GNU Grub Unified Boot Loader), which actually boots the operating system. These loaders in Linux , in case of a multi-boot configuration (more operating systems on a computer), permit the selection of the operating system to be booted. Lilo and Grub are installed or at the MBR (Master Boot Record), or at the first sector of the active partition.
In the following we will refer to LiLO as boot loader. This is usually installed in the boot sector, also known as MBR. If the user decides to boot Linux, LiLo will try to load the kernel. Now I will present step-by-step LiLo’s attempt to load the operating system.
1. In case of a multi-boot config, LiLo permits the user two choose an operating system from the menu. The LiLo settings are stored at /etc/lilo.conf. System administrators use this file for a very detailed finement of the loader. Here can be manually set what operating systems are installed, as well as the method for loading any of them. If on the computer there is only Linux, LiLo can be set to load directly the kernel, and skip the selection menu.
2. The Linux kernel is compressed, and contains a small bit, which will decompress it. Immediately after the first step begins the decompression and the loading of the kernel.
3. If the kernel detects that your graphics card supports more complex text modes, Linux allows the usage of them – this can be specified or during the recompilation of the kernel, or right inside Lilo, or other program, like rdev.
4. The kernel verifies hardware configuration (floppy drive, hard disk, network adapters, etc) and configures the drivers for the system. During this operation, several informative messages are shown to the user.
5. The kernel tries to mount the file system and the system files. The location of system files is configurable during recompilation, or with other programs – LiLo and rdev. The file system type is automatically detected. The most used file systems on Linux are ext2 and ext3. If the mount fails, a so-called kernel panic will occur, and the system will “freeze”.
System files are usually mounted in read-only mode, to permit a verification of them during the mount. This verification isn’t indicated if the files were mounted in read-write mode.
6. After these steps, the kernel will start init, which will become process number 1, and will start the rest of the system.
All about my Dear linux 