Frequently Asked Questions About Linux / UNIX » FAQ http://www.cyberciti.biz/faq Every answer asks a more beautiful question. Fri, 03 Feb 2012 22:38:32 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 Linux / Unix: Sed Substitute Multiple Patterns [ Find & Replace ]http://www.cyberciti.biz/faq/howto-sed-substitute-find-replace-multiple-patterns/ http://www.cyberciti.biz/faq/howto-sed-substitute-find-replace-multiple-patterns/#comments Fri, 20 Jan 2012 10:58:16 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11420 I'm using the date +'%D_%T' to store Unix system date and time in a shell variable called $_now:
_now="$(date +'%D_%T')" echo $_now Outputs: 01/20/12_16:10:42
I'd like to replace / and : with _. I'm aware of the following sed command:
sed 's/\//_/g > s/:/_/g' <<<"$_now" Outputs: 01_20_12_16_14_09
How do I specify two pattern within the same sed command to replace | and : with _ so that I can get output as 01_20_12_16_10_42?]]> http://www.cyberciti.biz/faq/howto-sed-substitute-find-replace-multiple-patterns/feed/ 1 Linux: Find Out My Machine (Host) Namehttp://www.cyberciti.biz/faq/find-my-linux-machine-name/ http://www.cyberciti.biz/faq/find-my-linux-machine-name/#comments Thu, 13 Jan 2011 21:27:03 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10487 How do I find out my server name (machine name) under Linux operating systems using command shell?]]> http://www.cyberciti.biz/faq/find-my-linux-machine-name/feed/ 0 Linux Install Google Chrome Browser [ Ubuntu, Suse, Debian, Fedora ]http://www.cyberciti.biz/faq/fedora-ubuntu-debian-suse-linux-install-googlechromebrowser/ http://www.cyberciti.biz/faq/fedora-ubuntu-debian-suse-linux-install-googlechromebrowser/#comments Wed, 06 Jan 2010 08:47:34 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=6248 How do I install Google Chrome browser under Linux operating systems? How do I install google-chrome-beta_current_amd64.deb or google-chrome-beta_current_x86_64.rpm file under Linux?]]> http://www.cyberciti.biz/faq/fedora-ubuntu-debian-suse-linux-install-googlechromebrowser/feed/ 18 Gnome Find Drive Serial Numberhttp://www.cyberciti.biz/faq/gnome-find-drive-serial-number/ http://www.cyberciti.biz/faq/gnome-find-drive-serial-number/#comments Sat, 03 Oct 2009 11:28:17 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5289 How do I find out serial number information for my hard disk under Ubuntu Linux Gnome desktop environment?]]> http://www.cyberciti.biz/faq/gnome-find-drive-serial-number/feed/ 4 Bash Script: Read One Character At A Timehttp://www.cyberciti.biz/faq/linux-unix-read-one-character-atatime-while-loop/ http://www.cyberciti.biz/faq/linux-unix-read-one-character-atatime-while-loop/#comments Wed, 30 Sep 2009 11:05:47 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5251 I need to count one character at a time from input.txt. How do I read one character at a time under Linux / UNIX bash shell script?]]> http://www.cyberciti.biz/faq/linux-unix-read-one-character-atatime-while-loop/feed/ 3 Help: Old Employees Accessing The Linux Serverhttp://www.cyberciti.biz/faq/former-employees-keep-accessing-linux-unix-server/ http://www.cyberciti.biz/faq/former-employees-keep-accessing-linux-unix-server/#comments Wed, 23 Sep 2009 14:38:52 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5219 I've recently noticed that two of my former employees are still accessing one of our Linux box. Old user account wasn't deleted because it has some important files. How do I make sure account get deleted without losing files and email stored in the account? Can you describe a terminations clearance policy for an employee account including email accounts, forwarding aliases, ssh / ftp, and access to vpn dialup services under Red Hat Enterprise Linux server?]]> http://www.cyberciti.biz/faq/former-employees-keep-accessing-linux-unix-server/feed/ 6 hdparm: HDIO_DRIVE_CMD(identify) Failed: Inappropriate Ioctl For Devicehttp://www.cyberciti.biz/faq/hdiodrive_cmdidentify-failed-inappropriate-ioctl-device/ http://www.cyberciti.biz/faq/hdiodrive_cmdidentify-failed-inappropriate-ioctl-device/#comments Sun, 23 Aug 2009 13:11:32 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4921 When I run hdparm -tT /dev/sda command under CentOS / RHEL I get the following error on screen:
/dev/sda: Timing buffered disk reads: 908 MB in 3.00 seconds = 302.39 MB/sec HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device

How do I fix this problem?]]> http://www.cyberciti.biz/faq/hdiodrive_cmdidentify-failed-inappropriate-ioctl-device/feed/ 0 Linux Disable / Remove All NFS Serviceshttp://www.cyberciti.biz/faq/centos-redhat-rhel-fedora-remove-nfs-services/ http://www.cyberciti.biz/faq/centos-redhat-rhel-fedora-remove-nfs-services/#comments Sun, 16 Aug 2009 09:19:14 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4834 NFS was not designed with security in mind, and has a number of weaknesses, both in terms of the protocol itself and because any NFS installation must expose several daemons, running on both servers and clients, to network attack. I use my CentOS based server only to server web pages and nothing else. How do I disable NFS services under RHEL / CentOS / Fedora Linux?]]> http://www.cyberciti.biz/faq/centos-redhat-rhel-fedora-remove-nfs-services/feed/ 7 How To Use awk In Bash Scriptinghttp://www.cyberciti.biz/faq/bash-scripting-using-awk/ http://www.cyberciti.biz/faq/bash-scripting-using-awk/#comments Sat, 15 Aug 2009 18:53:53 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4779 How do I use awk pattern scanning and processing language under bash scripts? Can you provide a few examples?]]> http://www.cyberciti.biz/faq/bash-scripting-using-awk/feed/ 22 Is Open Source Software Legal To Use For My Business?http://www.cyberciti.biz/faq/is-linux-open-source-software-legal-for-business/ http://www.cyberciti.biz/faq/is-linux-open-source-software-legal-for-business/#comments Fri, 07 Aug 2009 18:57:56 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4704 I can download and keep using free and open source software (FOSS) on multiple computers. Is this software legal to use for my business? Can you provide some legal information regarding usage of open source software for business which I can share with my boss? ]]> http://www.cyberciti.biz/faq/is-linux-open-source-software-legal-for-business/feed/ 2 Linux Tune Network Stack (Buffers Size) To Increase Networking Performancehttp://www.cyberciti.biz/faq/linux-tcp-tuning/ http://www.cyberciti.biz/faq/linux-tcp-tuning/#comments Wed, 20 May 2009 09:21:32 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3820 I've two servers located in two different data center. Both server deals with a lot of concurrent large file transfers. But network performance is very poor for large files and performance degradation take place with a large files. How do I tune TCP under Linux to solve this problem?]]> http://www.cyberciti.biz/faq/linux-tcp-tuning/feed/ 20 Debian / Ubuntu Linux Install Advanced Intrusion Detection Environment (AIDE) Softwarehttp://www.cyberciti.biz/faq/debian-ubuntu-linux-software-integrity-checking-with-aide/ http://www.cyberciti.biz/faq/debian-ubuntu-linux-software-integrity-checking-with-aide/#comments Mon, 18 May 2009 13:40:56 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3804 AIDE is an open source host-based intrusion detection system which is a replacement for the well-known Tripwire integrity checker. It provide software integrity checking and it can detect that intrusions (monitor filesystem for unauthorized change such as find out if system binaries modified and a new cracked versions installed or not) have occurred on the system. How do I install and configure AIDE under Ubuntu LTS / Debian Linux 5.0 server?]]> http://www.cyberciti.biz/faq/debian-ubuntu-linux-software-integrity-checking-with-aide/feed/ 3 Linux Uninstall VMWare Server Softwarehttp://www.cyberciti.biz/faq/linux-uninstall-vmware/ http://www.cyberciti.biz/faq/linux-uninstall-vmware/#comments Fri, 13 Mar 2009 21:38:39 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3460 In some cases I may need to uninstall VMware Server from my Linux system. I've VMWare server / Workstation software installed under CentOS / RHEL / Fedora Linux. How do I uninstall VMWare under Linux?]]> http://www.cyberciti.biz/faq/linux-uninstall-vmware/feed/ 5 Linux Iptables Just Block By Countryhttp://www.cyberciti.biz/faq/block-entier-country-using-iptables/ http://www.cyberciti.biz/faq/block-entier-country-using-iptables/#comments Mon, 02 Mar 2009 20:15:04 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3402 I admin ecom website and a lot of bogus traffic comes from countries that do not offer much in commercial value. How do I just configure Apache or iptables to just refuse connections to certain countries?]]> http://www.cyberciti.biz/faq/block-entier-country-using-iptables/feed/ 109 Apache: Graceful Server Reboot From Shellhttp://www.cyberciti.biz/faq/apache-httpd-graceful-server-reboot-from-shell/ http://www.cyberciti.biz/faq/apache-httpd-graceful-server-reboot-from-shell/#comments Tue, 27 Jan 2009 05:39:38 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5545 How do I gracefully restart Apache web server from a shell prompt?]]> http://www.cyberciti.biz/faq/apache-httpd-graceful-server-reboot-from-shell/feed/ 0 Bash Clear DNS Cachehttp://www.cyberciti.biz/faq/bash-clear-dns-cache/ http://www.cyberciti.biz/faq/bash-clear-dns-cache/#comments Mon, 26 Jan 2009 15:21:42 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5490 How do I clear DNS cache using BASH shell prompt under UNIX like operating systems?]]> http://www.cyberciti.biz/faq/bash-clear-dns-cache/feed/ 0 Red Hat / CentOS: Check / List Running Serviceshttp://www.cyberciti.biz/faq/check-running-services-in-rhel-redhat-fedora-centoslinux/ http://www.cyberciti.biz/faq/check-running-services-in-rhel-redhat-fedora-centoslinux/#comments Wed, 14 Jan 2009 19:48:16 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=3065 Q. How do I list all currently running services in Fedora / RHEL / CentOS Linux server?]]> http://www.cyberciti.biz/faq/check-running-services-in-rhel-redhat-fedora-centoslinux/feed/ 11 Find out Apache Versionhttp://www.cyberciti.biz/faq/find-out-apache-version/ http://www.cyberciti.biz/faq/find-out-apache-version/#comments Sat, 20 Dec 2008 06:58:19 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=2911 Q. I have a rented dedicated LAMP server and I need to know what version of Apache I am running. How do I find out my Apache server version? How do I find out what modules loaded?]]> http://www.cyberciti.biz/faq/find-out-apache-version/feed/ 13 How To Setup Vanity DNS Name Server Using BIND 9http://www.cyberciti.biz/faq/linux-unix-bind9-set-vanity-dns-nameserver/ http://www.cyberciti.biz/faq/linux-unix-bind9-set-vanity-dns-nameserver/#comments Fri, 18 Jul 2008 10:11:31 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=1198 http://www.cyberciti.biz/faq/linux-unix-bind9-set-vanity-dns-nameserver/feed/ 6 How To Specify and Browse Website Using IPv6 Address With Firefox, Opera Web Browserhttp://www.cyberciti.biz/faq/how-can-ipv6-address-used-with-webbrowser/ http://www.cyberciti.biz/faq/how-can-ipv6-address-used-with-webbrowser/#comments Fri, 11 Jul 2008 10:25:31 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=1184 Now, I know how to configure IPv6 tunnel but how do I browse website using IPv6 IP address like 2001:4860:0:2001::68 under Firefox or Opera web browser?]]> http://www.cyberciti.biz/faq/how-can-ipv6-address-used-with-webbrowser/feed/ 16