nixCraft » Howto http://www.cyberciti.biz/tips This is a Linux sys admin journal by Vivek about sys admin work, Linux tips & tricks, hacks, news and more. Fri, 03 Feb 2012 22:45:35 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 HowTo: Create sar Graphs With kSar [ Identifying Linux Bottlenecks ]http://www.cyberciti.biz/tips/identifying-linux-bottlenecks-sar-graphs-with-ksar.html http://www.cyberciti.biz/tips/identifying-linux-bottlenecks-sar-graphs-with-ksar.html#comments Tue, 15 Dec 2009 06:33:21 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=6165 The sar command collect, report, or save UNIX / Linux system activity information. It will save selected counters in the operating system to the /var/log/sa/sadd file. From the collected data, you get lots of information about your server:
  1. CPU utilization
  2. Memory paging and its utilization
  3. Network I/O, and transfer statistics
  4. Process creation activity
  5. All block devices activity
  6. Interrupts/sec etc.

sar output can be used for identifying server bottlenecks. However, analyzing information provided by sar can be difficult, so use kSar, which can take sar output and plot a nice easy to understand graph over period of time. ]]> http://www.cyberciti.biz/tips/identifying-linux-bottlenecks-sar-graphs-with-ksar.html/feed 21 Linux / Windows Application For Prevention Of RSI (Repetitive Strain Injury)http://www.cyberciti.biz/tips/repetitive-strain-injury-prevention-software.html http://www.cyberciti.biz/tips/repetitive-strain-injury-prevention-software.html#comments Wed, 04 Nov 2009 05:21:00 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5950 workrave-image Repetitive strain injury (RSI) is occupational overuse syndrome, non-specific arm pain or work related upper limb disorder. RSI caused from overusing the hands to perform a repetitive task, such as typing, writing, or clicking a mouse. Unfortunately, most people do not understand what RSI is or how serious it can be. You can easily prevent RSI using open source software called Workrave.]]> http://www.cyberciti.biz/tips/repetitive-strain-injury-prevention-software.html/feed 14 20 Linux Server Hardening Security Tipshttp://www.cyberciti.biz/tips/linux-security.html http://www.cyberciti.biz/tips/linux-security.html#comments Fri, 30 Oct 2009 07:52:11 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5687 Securing your Linux server is important to protect your data, intellectual property, and time, from the hands of crackers (hackers). The system administrator is responsible for security Linux box. In this first part of a Linux server security series, I will provide 20 hardening tips for default installation of Linux system.]]> http://www.cyberciti.biz/tips/linux-security.html/feed 102 Use a Linux LiveCD to Avoid Windows Malware For Netbankinghttp://www.cyberciti.biz/tips/use-linux-live-cd-usb-for-online-banking.html http://www.cyberciti.biz/tips/use-linux-live-cd-usb-for-online-banking.html#comments Thu, 15 Oct 2009 12:53:55 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5791 Internet has revolutionized the way online users can shop and avail banking services like internet Banking from anywhere, anytime without visiting bank. But, how safe is your money with online net-banking which allows to carry out money transfer? Companies and in some case individuals lost anywhere from $10,000 to $500,000 dollars because of a single malware infection. The cyber crooks are targeting innocent MS-Windows user. If you are concerned about how best to protect yourself from this type of fraud, use Linux LiveCD for online banking and avoid Microsoft Windows at all cost.]]> http://www.cyberciti.biz/tips/use-linux-live-cd-usb-for-online-banking.html/feed 6 Celestia 3D Space Simulation Software For Linux / Windows / OS Xhttp://www.cyberciti.biz/tips/celestia-astronomy-linux-program.html http://www.cyberciti.biz/tips/celestia-astronomy-linux-program.html#comments Wed, 30 Sep 2009 23:20:07 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5745 celestia-europe-Io-jupiter Celestia is a real-time visual space simulation astronomy program. It is a cross platform, open source software and released under the GNU General Public License. NASA and ESA have used Celestia in their educational and for interfacing to trajectory analysis software. It allows users to travel through an extensive universe, modeled after reality, at any speed, in any direction and at any time in history. Celestia displays and interacts with objects ranging in scale from artificial satellites to entire galaxies in three dimensions using OpenGL. It is a perfect software for astronomer, educator, student, and teacher for astronomy purpose.]]> http://www.cyberciti.biz/tips/celestia-astronomy-linux-program.html/feed 11 How To: Upgrade Red Hat Enterprise Linux 5.3 to v5.4http://www.cyberciti.biz/tips/red-hat-enterprise-linux-5-4-released.html http://www.cyberciti.biz/tips/red-hat-enterprise-linux-5-4-released.html#comments Wed, 02 Sep 2009 18:22:59 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5708 Red Hat Enterprise Linux v5.4 has been released and available via RHN for immediate update. The new version includes the kernel-based virtual machine (KVM) virtualization, next generation of developer features and tools including GCC 4.4, a new malloc(). Also included clustered, high-availability filesystem to support Microsoft Windows storage needs on Red Hat Enterprise Linux.]]> http://www.cyberciti.biz/tips/red-hat-enterprise-linux-5-4-released.html/feed 24 BIND 9 Dynamic Update DoS Security Updatehttp://www.cyberciti.biz/tips/bind-dynamic-update-dos.html http://www.cyberciti.biz/tips/bind-dynamic-update-dos.html#comments Wed, 29 Jul 2009 15:47:12 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5570 BIND 9 is an implementation of the Domain Name System (DNS) protocols. named daemon is an Internet Domain Name Server for UNIX like operating systems. Dynamic update messages may be used to update records in a master zone on a nameserver. When named receives a specially crafted dynamic update message an internal assertion check is triggered which causes named to exit. An attacker which can send DNS requests to a nameserver can cause it to exit, thus creating a Denial of Service situation. configuring named to ignore dynamic updates is NOT sufficient to protect it from this vulnerability. This exploit is public. Please upgrade immediately.]]> http://www.cyberciti.biz/tips/bind-dynamic-update-dos.html/feed 7 Top 20 OpenSSH Server Best Security Practiceshttp://www.cyberciti.biz/tips/linux-unix-bsd-openssh-server-best-practices.html http://www.cyberciti.biz/tips/linux-unix-bsd-openssh-server-best-practices.html#comments Fri, 24 Jul 2009 21:49:43 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5489 Don't tell anyone that I'm free OpenSSH is the implementation of the SSH protocol. OpenSSH is recommended for remote login, making backups, remote file transfer via scp or sftp, and much more. SSH is perfect to keep confidentiality and integrity for data exchanged between two networks and systems. However, the main advantage is server authentication, through the use of public key cryptography. From time to time there are rumors about OpenSSH zero day exploit. Here are a few things you need to tweak in order to improve OpenSSH server security.]]> http://www.cyberciti.biz/tips/linux-unix-bsd-openssh-server-best-practices.html/feed 106 Vmware Linux Guest Add a New Hard Disk Without Rebooting Guesthttp://www.cyberciti.biz/tips/vmware-add-a-new-hard-disk-without-rebooting-guest.html http://www.cyberciti.biz/tips/vmware-add-a-new-hard-disk-without-rebooting-guest.html#comments Sat, 18 Jul 2009 06:55:53 +0000 Vivek Gite /sys/class/scsi_host/host#/scan]]> http://www.cyberciti.biz/tips/?p=5411 As a system admin, I need to use additional hard drives for to provide more storage space or to separate system data from user data. This procedure, adding physical block devices to virtualized guests, describes how to add a hard drive on the host to a virtualized guest using VMWare software running Linux as guest.

It is possible to add or remove a SCSI device explicitly, or to re-scan an entire SCSI bus without rebooting a running Linux VM guest. This how to is tested under Vmware Server and Vmware Workstation v6.0 (but should work with older version too). All instructions are tested on RHEL, Fedora, CentOS and Ubuntu Linux guest / hosts operating systems. ]]> http://www.cyberciti.biz/tips/vmware-add-a-new-hard-disk-without-rebooting-guest.html/feed 30 6 Tools To Find Out Website Load Speedhttp://www.cyberciti.biz/tips/website-load-speed-performace-testing-tools.html http://www.cyberciti.biz/tips/website-load-speed-performace-testing-tools.html#comments Wed, 15 Jul 2009 17:42:34 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5346 Research shows that if your web pages take longer than 5 seconds to load, you lose 50% of your viewers and sales. As a UNIX admin often end users and web developers complain about website loading speed and timings. Usually, there is nothing wrong with my servers or server farm. Fancy java script and images / flash makes site pretty slow. These tools are useful to debug performance problems for sys admins, developers and end users. Here are six tools that can analyzes web pages and tells you why they are slow. Use the following tools to:
  • Make your site faster.
  • Debug site problem, especially client side and server side stuff.
  • Better user experience.
  • Improve the web.
]]> http://www.cyberciti.biz/tips/website-load-speed-performace-testing-tools.html/feed 24 Lighttpd Traffic Shaping: Throttle Connections Per Single IP (Rate Limit)http://www.cyberciti.biz/tips/lighttpd-set-throughput-connections-per-ip.html http://www.cyberciti.biz/tips/lighttpd-set-throughput-connections-per-ip.html#comments Sun, 21 Jun 2009 00:02:13 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5148 If you do not control or throttle end users, your server may run out of resources. Spammers, abuser and badly written bots can eat up all your bandwidth. A webserver must keep an eye on connections and limit connections per second. This is serving 101. The default is no limit. Lighttpd can limit the throughput for each single connection (per IP) or for all connections. You also need to a use firewall to limit connections per second. In this article I will cover firewall and lighttpd web server settings to throttle end users. The firewall settings can be applied to other web servers such as Apache / Nginx and IIS server behind PF / netfilter based firewall.]]> http://www.cyberciti.biz/tips/lighttpd-set-throughput-connections-per-ip.html/feed 15 Visual Representations Of Linux File Systemshttp://www.cyberciti.biz/tips/visual-representations-of-linux-file-systems.html http://www.cyberciti.biz/tips/visual-representations-of-linux-file-systems.html#comments Tue, 16 Jun 2009 19:49:38 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=5079 This is an interesting visualization techniques for software analysis. From the article:
Despite being a very important part of any operating system, file systems tend to get little attention. Linux has three editions for Linux Device Drivers, another three for Understanding the Linux Kernel and two for Linux Kernel Development. The first is a detail analysis of one particular Linux Kernel tree and the second is a shorter one done over a large number of file systems from Linux Kernel 2.6.0 to 2.6.29. After that there is a small section that shows some aspects of the BSD family. After conclusions there is an appendix consisting of three things: the first one explains how the file systems for Linux were compiled, the second one shows timelines for the releases of Linux Kernel, FreeBSD, NetBSD and OpenBSD; the last is a detailed map of the external symbols of the kernel modules analyzed in the second section.

A Visual Expedition Inside the Linux File Systems]]> http://www.cyberciti.biz/tips/visual-representations-of-linux-file-systems.html/feed 4 Increase Your VMware Virtual Hard Disk Size ( vmdk file )http://www.cyberciti.biz/tips/howto-resize-vmware-virtual-harddisk-size.html http://www.cyberciti.biz/tips/howto-resize-vmware-virtual-harddisk-size.html#comments Tue, 09 Jun 2009 14:22:42 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4998 I've Windows Vista installed as a guest under Ubuntu Linux using VMWARE Workstation 6.0. This is done for testing purpose and browsing a few site that only works with Internet Explorer. Since I only use it for testing I made 16GB for Vista and 5GB for CentOS and 5GB in size for FreeBSD guest operating systems. However, after some time I realized I'm running out of disk space under both CentOS and Vista. Adding a second hard drive under CentOS solved my problem as LVM was already in use. Unfortunately, I needed to double 32GB space without creating a new D: drive under Windows Vista. Here is a simple procedure to increase your Virtual machine's disk capacity by resizing vmware vmdk file.]]> http://www.cyberciti.biz/tips/howto-resize-vmware-virtual-harddisk-size.html/feed 25 Linux Find Out If PCI Hardware Supported or Not In The Current Running Kernelhttp://www.cyberciti.biz/tips/linux-find-supported-pci-hardware-drivers.html http://www.cyberciti.biz/tips/linux-find-supported-pci-hardware-drivers.html#comments Wed, 03 Jun 2009 15:05:04 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4971 From my mailbag:
How do I find out if a given PCI hardware is supported of by the current CentOS / Debian / RHEL / Fedora Linux kernel?
You can easily find out find out if a given piece of PCI hardware such as RAID, network, sound, graphics card is supported or not by the current Linux kernel using the following utilities under any Linux distributions.]]> http://www.cyberciti.biz/tips/linux-find-supported-pci-hardware-drivers.html/feed 9 OpenOffice.org Quick Introduction For New Userhttp://www.cyberciti.biz/tips/openofficeorg-new-user-orientation.html http://www.cyberciti.biz/tips/openofficeorg-new-user-orientation.html#comments Wed, 03 Jun 2009 11:26:39 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4967 OpenOffice.org (OOo) is a freely available, full-featured office suite. OOo is both a software product and a community of volunteers that produces and supports the software. However, new users may get lost while finding help, support and productivity enhancing extensions. This blog post covers OOo new user orientation to to discover support, tutorials, community insights, templates, clip art, extensions, and blogs for OOo. ]]> http://www.cyberciti.biz/tips/openofficeorg-new-user-orientation.html/feed 0 Linux x86_64: Detecting Hardware Errorshttp://www.cyberciti.biz/tips/linux-server-predicting-hardware-failure.html http://www.cyberciti.biz/tips/linux-server-predicting-hardware-failure.html#comments Tue, 02 Jun 2009 21:54:58 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4951 The Blue Screen of Death (BSoD) is used for the error screen displayed by Microsoft Windows, after encountering a critical system. Linux / UNIX like operating system may get a kernel panic. It is just like BSoD. The BSoD and a kernel panic generated using a Machine Check Exception (MCE). MCE is nothing but feature of AMD / Intel 64 bit systems which is used to detect an unrecoverable hardware problem.

Program such mcelog decodes machine check events (hardware errors) on x86-64 machines running a 64-bit Linux kernel. It should be run regularly as a cron job on any x86-64 Linux system. This is useful for predicting server hardware failure before actual server crash.]]> http://www.cyberciti.biz/tips/linux-server-predicting-hardware-failure.html/feed 6 ss: Display Linux TCP / UDP Network and Socket Informationhttp://www.cyberciti.biz/tips/linux-investigate-sockets-network-connections.html http://www.cyberciti.biz/tips/linux-investigate-sockets-network-connections.html#comments Tue, 02 Jun 2009 12:56:31 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4940 The ss command is used to dump socket statistics. It allows showing information similar to netstat command. It can display more TCP and state information than other tools. It is a new, incredibly useful and faster (as compare to netstat) tool for tracking TCP connections and sockets. SS can provide information about:
  • All TCP sockets.
  • All UDP sockets.
  • All established ssh / ftp / http / https connections.
  • All local processes connected to X server.
  • All the tcp sockets in state FIN-WAIT-1 and much more.
]]> http://www.cyberciti.biz/tips/linux-investigate-sockets-network-connections.html/feed 9 Lighttpd mod_rrdtool: Monitor The Load, Requests Per Seconds and Traffichttp://www.cyberciti.biz/tips/rhel-fedora-centos-debian-ubuntu-lighttpd-mod_rrdtool.html http://www.cyberciti.biz/tips/rhel-fedora-centos-debian-ubuntu-lighttpd-mod_rrdtool.html#comments Sat, 23 May 2009 09:53:22 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4878 The round-robin database tool aims to handle time-series data like network bandwidth, temperatures, CPU load etc. The data gets stored in round-robin database so that system storage footprint remains constant over time. Lighttpd comes with mod_rrdtool to monitor the server load and other details. This is useful for debugging and tuning lighttpd / fastcgi server performance. ]]> http://www.cyberciti.biz/tips/rhel-fedora-centos-debian-ubuntu-lighttpd-mod_rrdtool.html/feed 8 Red Hat / CentOS VSFTPD FTP Server Configurationhttp://www.cyberciti.biz/tips/rhel-fedora-centos-vsftpd-installation.html http://www.cyberciti.biz/tips/rhel-fedora-centos-vsftpd-installation.html#comments Thu, 21 May 2009 18:06:12 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4788 vsftpd (Very Secure FTP Daemon) is an FTP server for UNIX-like systems, including CentOS / RHEL / Fedora and other Linux distributions. It supports IPv6, SSL, locking users to their home directories and many other advanced features.

In this guide you will learn:
  1. Setup vsftpd to Provide FTP Service.
  2. Configure vsftpd.
  3. Configure Firewalls to Protect the FTP Server.
  4. Configure vsftpd with SSL/TLS.
  5. Setup vsftpd as Download Only Anonymous Internet Server.
  6. Setup vsftpd With Virtual Users and Much More.


Read CentOS / RHEL FTP Server Series:]]> http://www.cyberciti.biz/tips/rhel-fedora-centos-vsftpd-installation.html/feed 36 Linux HugeTLBfs: Improve MySQL Database Application Performancehttp://www.cyberciti.biz/tips/linux-hugetlbfs-and-mysql-performance.html http://www.cyberciti.biz/tips/linux-hugetlbfs-and-mysql-performance.html#comments Wed, 20 May 2009 07:59:39 +0000 Vivek Gite http://www.cyberciti.biz/tips/?p=4773 Applications that perform a lot of memory accesses (several GBs) may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses. HugeTLBfs is memory management feature offered in Linux kernel, which is valuable for applications that use a large virtual address space. It is especially useful for database applications such as MySQL, Oracle and others. Other server software(s) that uses the prefork or similar (e.g. Apache web server) model will also benefit.

The CPU's Translation Lookaside Buffer (TLB) is a small cache used for storing virtual-to-physical mapping information. By using the TLB, a translation can be performed without referencing the in-memory page table entry that maps the virtual address. However, to keep translations as fast as possible, the TLB is usually small. It is not uncommon for large memory applications to exceed the mapping capacity of the TLB. Users can use the huge page support in Linux kernel by either using the mmap system call or standard SYSv shared memory system calls (shmget, shmat). ]]> http://www.cyberciti.biz/tips/linux-hugetlbfs-and-mysql-performance.html/feed 10