Amazon S3 is a widely used public cloud storage system. S3 allows an object/file to be up to 5TB which is enough for most applications. The AWS Management Console provides a Web-based interface for users to upload and manage files in S3 buckets. However, uploading a large files that is 100s of GB is not…
After the post Fetching RSS Feed and Outputing Feed Items as HTML in PHP was originally published, there are some updates such as adding a simple RSS feed caching mechanism and supporting scanning content parts of the feed items for images. Recently, Webucator makes a great tutorial video on introducing the RSS to HTML PHP…
PowerPoint uses 96 dots per inch (dpi) by default when you export a slide. The DPI of the images like .tif ones exported from PowerPoint are always 96. In the options of PowerPoint, there is a setting for choosing DPIs. However, it have no effect. For some needs like images for printing posters, larger DPIs…
As you may know, Adobe stopped supporting the NPAPI version of Flash on Linux and the latest NPAPI version of Flash player at version 11.2 released back in 2012 will only receive security fixes. Even the security fixes to the 11.2 version of the Flash Plugin your Firefox is using will end on May 4,…
SSH is a very common tool for Linux/Unix platforms. One annoying problem when using SSH is that the connection may get disconnected if the SSH connection is idle for some time under common configurations. Users may run an infinite loop like while true; do uptime; sleep 30; done when there is no work to be…
It is common practice to calculate the checksums for files to check its integrity. For large files, the checksum computation is slow. Now I am wondering why it is so slow and whether choosing another tool will be better. In this post, I try three common tools md5sum, sha1sum and crc32 to compute checksums on…
Doing actions upon changes of files and directories is very useful. Examples like compiling a project after the source code files are changed, sending emails after important configuration files are modified, building the PDF after a TeX file is modified. On Linux, the inotify-tools provide good support for trigger actions after changes. In this post,…
The hplip packages contains all the tools you need to set up the HP scanner. For scanning, you may use the sane and xsane tools. The tricky part to enable the scanner is carefully choose which driver to use from the hplip package. If you choose a non-suitable driver, only the printer will work and…
RAID systems such as MegaRAID add signatures to disks to maintain the infomration on these didks. When we simply remove these disks and install them to another server, Linux on the new server may detect these RAID signature infomration and refuses to continue write to the disk. Here is one example that mkfs reports “apparently…
Grub2 config file may need to be re-generated after changing Grub2 configurations such as configuration changes and setting default boot entries. The Grub2’s config file may be at different locations depending on your Linux distro and whether your Linux is booted in BIOS or UEFI mode. This makes regenerating Grub2 config file not easy for…
It is common for programs to write to files in filesystems on disks. However, what if the disk was almost full when your program writes to the filesystem on a disk? For systems software and mission critical programs, it is a better or must-to-do practice to check the available filesystem space before actually writing to…
Vim is pretty fast and powerful. However, the core of Vim is (yet) single-threaded (some discussions and tries on porting Vim to be multi-threading, but not yet there). This means some functions that are slow will block Vim there and you have to wait for it. While Vim is fast, some plugins are not. When…
You may be aware of the GitHub’s largest DDoS attack in history on Mar. 27, 2015 (some context, technical details, and discussions): We've been under continuous DDoS attack for 24+ hours. The attack is evolving, and we're all hands on deck mitigating. — GitHub Status (@githubstatus) March 27, 2015 One important technique when facing this…
First time getting my hand on a plotter (HP Designjet 500) directly to print a poster, I found it was an interesting experience. But configuring the printer settings was not that straightforward compared to using normal office A4 printers. I took photos of how it was configured for reference of my own and also those…
Controlling the mounting of filesystems is a useful technique for managing Linux systems. The mounting configurations are mostly in the /etc/fstab file. In this post, we will discuss 2 common and useful techniques for controlling the filesystem mounting by playing with the /etc/fstab file: allowing non-root users to mount/unmount filesystems and avoiding mounting failures blocking…
You may already well know “Linux” and may also use the “operating system based on the Linux kernel” directly or indirectly (you are indirectly using it now as this site is hosted on Linux). But how should we name the OS based on Linux? You may know there is GNU/Linux naming controversy. Different people have…
It is useful to show the feed items directly on the webpage as HTML content. In this ost, we will show one single PHP function that fetches an RSS feed and outputs the feed items as HTML elements in the web page. One example to fetch an RSS feed and output the itmes as HTML…
SSD is common for VPS and PaaS virtual machines for higher I/O performance. Now, it is coming to shared hosting too. DreamHost states that “Now with solid state drives (SSDs), our standard web hosting loads pages 200% faster”. We ourselves are happy to know this performance improvement with the price kept the same. Good work,…
VPNs are useful for testing viewing webpages from a remote location or visiting blocked websites. In this post, I will introduce a method for finding and using free VPNs on iPhone. Note that the VPNs are free and the providers are not identified. Hence, only use this method for visiting public webpages or keeping visiting…
Note that this was only tested on certain combinations like this (Windows 7 with iOS 8), this (Windows 7 with iOS 7), this and this (Windows 7 with iOS 9.3.2 (iphone 6s)). Windows 7 seems a possible Windows OS that can work. Recently, I tested it on Windows 8 and iOS 9. Unfortunately, it did…