Frequently Asked Questions About Linux / UNIX » UNIX

Nginx: SPDY SSL Installation and Configuration On Debian / Ubuntu

nixCraft — Sun, 19 May 2013 15:24:36 +0000

Google Chrome/Chromium, Firefox and Opera browser support SPDY networking protocol. It enables faster browsing on supported sites. SPDY is similar to HTTP, with particular goals to reduce web page load latency and improve web security. SPDY achieves reduced latency through compression, multiplexing, and prioritization. How do I enable nginx SPDY support running on Debian or Ubuntu Linux server?

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Linux / Unix: View Overlapping Man Page With Same Names

nixCraft — Thu, 16 May 2013 19:06:02 +0000

I am a new Unix / Linux user. I am using whatis command to find man pages. But, I noticed that some man pages have a common names. For example, when I run whatis printf:
Outputs:
printf (1) - format and print data printf (1p) - write formatted output printf (3) - formatted output conversion printf (3p) - print formatted output printf [builtins] (1) - bash built-in commands, see bash(1)
How do I access overlapping man pages and what is the meaning of (1), (1p), (3), and so on?

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scp: Do not Overwrite Existing File On Linux or Unix System

nixCraft — Fri, 10 May 2013 20:03:49 +0000

I am a new Linux user. I use scp to upload files to net-storage provided CDN company. I do not want to overwrite the existing files. How can I prevent overwriting of files when using scp command under Linux, Mac OS X or Unix like operating systems?

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Linux / Unix: Find All Hidden Dot Directories and Delete

nixCraft — Sun, 05 May 2013 18:27:16 +0000

I need to clean up my backups stored on the nas server. I need to free up the disk space. How do I find out all hidden dot directories such as /nas01/backups/home/user/.gnome/, /nas01/backups/home/user/.gnome/ and so on and delete then in a single pass using Linux or Unix command line option? Please note that I do not want to delete nested hidden directories such as /nas01/backups/home/user/data/.xml, /nas01/backups/home/user/foo/bar/.level/.levle2/ and so on.

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Linux / Unix: Dig Command Find Out TTL (Time to Live) Value For DNS Records

nixCraft — Sun, 05 May 2013 05:53:32 +0000

I would like to see the Time-to-live (TTL) value for a 'AAAA' and A record for domains. How do I see Time-to-live (TTL) for a DNS record under Unix or Linux operating systems using command line options?

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Vi / Vim: Wipe and Undo All Changes Since Opening a File

nixCraft — Sun, 28 Apr 2013 20:11:25 +0000

I am a new vi / vim text editor user and I know how to quit without saving changes. What if I want to wipe out all of the edits I have made in a session and get back to the original file? How do I wipe all changes since opening a file?

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Apache 2: Reload HTTPD Configuration File Without Restarting Apache Config Changes

nixCraft — Sun, 28 Apr 2013 03:47:32 +0000

I made changes to the httpd.conf file. How do I reload the new config changes without restarting the Apache 2 web server under Debian / CentOS Linux operating systems?

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Linux / Unix: Shell Remove Empty Lines

nixCraft — Wed, 24 Apr 2013 20:46:54 +0000

I am a new Linux user. I have text files with lots of empty lines. How do I delete all empty lines under Linux or Unix operating systems?

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Bash: .* Considered Harmful To Match Dot Files. Why?

nixCraft — Wed, 24 Apr 2013 19:49:53 +0000

How do I match dot files under Unix / Linux using bash shell? Why .* considered as harmful when matching dot files under bash shell?

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HowTo: Unix rm All Files In a Directory

nixCraft — Wed, 24 Apr 2013 10:03:53 +0000

I am a new Unix user. How do I rm (remove) all files in a directory called personal-files under Unix like operating systems?

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Bash Function: Find Number Of Arguments Passed

nixCraft — Wed, 24 Apr 2013 10:02:59 +0000

How do I find out number of arguments passed to my bash function called foo() under Unix like operating systems?

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HowTo: Check If a Directory Exists In a Shell Script

nixCraft — Sun, 14 Apr 2013 19:17:49 +0000

How do I check if a directory exists in a shell script under Linux or Unix like operating systems?

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VIM: Jump Back To Previous or Last Cursor Position

nixCraft — Sun, 14 Apr 2013 18:44:00 +0000

Writing shell scripts in vim I usually go search for functions or something. Copy lines and then go back to where I was and modify the code. However, I need to manually navigate way back to the previous / last position. How can I automatically go back to where I was when I started my search operation under vim?

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AWK: Remove All Blank Spaces From String / Field

nixCraft — Sun, 14 Apr 2013 18:14:54 +0000

I need to parse the following text file: # example.net config user = www30021 group = ftp30020 uid = 30021 gid = 30020 tmp_path = /netapp42/shared/www/images/host.example.com/tmp.bin tmp_perms = defaults,nodev,nosuid,noexec jail = on location = /jails/apache/h/host.example.com/ sftp = on ftps = off php-cgi = on perl-cgi = off I need to find out value for each field and remove any blank spaces / white spaces from the field. How do I solve this problem using awk under Linux or Unix like operating systems?

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Nginx: Block URL Access (wp-admin/wp-login.php) To All Except One IP Address

nixCraft — Sun, 14 Apr 2013 09:07:13 +0000

I am the small business owner and runs my own web-site. I have noticed increased cracking activity against by blog. What's the best way to block WordPress URLs such as example.com/blog/wp-login.php and example.com/blog/wp-admin/ in the nginx web-server?

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Apache / Nginx / Lighttpd: PHP Disable File Upload

nixCraft — Sun, 14 Apr 2013 07:31:55 +0000

I am in the process of setting Apache and PHP for my small business server. I'm not utilizing file upload functionality in any of my PHP scripts. How do I disallow uploading files under CentOS or Ubuntu Linux based LAMP server?

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Linux / Unix: Use rsync Command Over FTP

nixCraft — Tue, 09 Apr 2013 20:04:03 +0000

How do I use rsync command to sync files to a remote host called web-42.vps running VSFTPD ftp server? Can you give me rsync ftp example for Unix like operating systems?

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Linux / Unix Shell Script: Get The Current Directory

nixCraft — Tue, 09 Apr 2013 10:36:04 +0000

I am working on a shell script. I need to find out the current working directory. How do I get the current working directory under Bash or Ksh shell running on Linux or Unix like operating systems?

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FreeBSD: Delete User Account Command

nixCraft — Tue, 09 Apr 2013 09:21:22 +0000

How do I remove the tom user under FreeBSD operating system using command line options?

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Linux: Jpeg Image Optimization / Compress Command

nixCraft — Tue, 09 Apr 2013 09:21:07 +0000

I know how to optimize and compress png images using optipng command. line tool. I have lots of images in JPEG format. How do I compress and optimize JPEG images on my amazon cloud account so that I can save bandwidth on cloudfront cdn account? How do I use an image compressor to create lossless compression on JPEG files, with no effect on image quality in bulk using Linux?

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