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  A possible way to recover deleted files on Linux

Last week I was generating a MD5 sum for an virtual machine image on one OpenNebula server: # ls -l test.img -rw-r--r-- 1 root root 10486808576 Oct 12 02:21 test.img # md5sum test.img At the same time I was clearing the files on the server on another terminal and deleted the above image file mistakenly with : # rm test.img Since this image file is 10GB, it took some time to remove this file from the server, so I used the Ctrl+Z command to suspend the remove command. [1]+ Stopped ...

   Linux,File,Recovery     2013-11-26 07:03:37

  Implement struct no copy in GoLang

There is some case where some of the struct in GoLang which is not meant to be copied. For example, sometimes a global configuration which should have only one version passed around the whole application and should not be copied and modified. In GoLang, there is no intuitive solution on preventing copying of struct. But there is still some way which can be leveraged to help prevent this while developing the code. The trick is to define some struct implementing sync.Locker interface and has this ...

   GO VET,NOCOPY,NO COPY     2020-09-04 22:24:58

  How to undo git changes?

When using git for version control, there is frequent need on undoing commits due to some unexpected changes. This post will introduce how to undo changes with git command in different cases. Undo commit A common undo case is that some commit needs to be reverted as the commit contains error. In this case, the code is already committed. The command to revert the commit is git revert HEAD This command will add new a commit to the existing head to undo the previous commit. It will not change the p...

   GIT,GIT RESET,GIT REVERT,GIT CHECKOUT     2019-12-28 02:21:47

  Migrate from MySQL to MariaDB in Ubuntu

The biggest movement of escaping from MySQL in this century starts, openSUSE,Fedora and Arch have started to use MariaDB instead of MySQL as their default database. Many people also dislike the attitude of Oracle on MySQL, so it's reasonable to migrate from MySQL to MariaDB. The whole process is not complicated. Here we share the steps to migrate from MySQL to MariaDB in Ubuntu. Installation procedure: sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 0xcbcb082a1bb943db Modify /etc/a...

   MySQL,MariaDB,Ubuntu     2013-08-13 11:14:51

  Easy Parallel Processing in PHP

The proliferation of multicore CPUs and the inability of our learned CPU vendors to squeeze many more GHz into their designs means that often the only way to get additional performance is by writing clever parallel software. One problem we were having is that some of our batch processing jobs were taking too long to run. In order to speed the processing, we tried to split the processing file into half, and let a separate PHP process run each job. Given that we were using a dual core serv...

   PHP,Parallel processing,Multithreading like,Sleep     2011-12-12 10:58:59

  Some cases where MySQL cannot be started

After installing MySQL, when we try to start MySQL, sometimes we may not be able to start it. The reasons can be different. We share some general cases where MySQL cannot be started. Case 1: Directory or file permission issue If the permission is set wrongly in MySQL's $datadir and its sub directories or files, MySQL will not be able to read and write files normally. Error message: mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/data /usr/local/mysql/bin/mysqld_safe: lin...

   MySQL,Error,Log     2013-08-15 03:32:36

  A simple tutorial about CSS flex property

CSS Flexbox is a layout module that makes it easier to create flexible and responsive layouts in CSS. It provides a simple and powerful way to align elements within a container and distribute space between them. To use flexbox, you need to set the display property of an element to "flex". You can do this by adding the following rule to your CSS: .container { display: flex; } The flex container will now have two main axes: the main axis and the cross axis. By default, the main axis runs horizo...

   JUSTIFY-CONTENT,FLEX,CSS     2022-12-25 06:44:34

  Push docker image to remote AWS ECR

With the popularity of distributed and large-scale systems, there are more and more adoptions of cloud services. One of the most popular container in the market is Docker and one of the most popular cloud service provider is AWS. From development perspective, there is frequent need to push local docker image to remote ECR for debugging or testing purpose. Normally when a code change is done and the committed change would go through a series of process like code review, push to remote repo, merge...

   CLOUD,AWS,DOCKER,AWS ECR     2020-12-13 04:12:26

  JavaScript finite state machine

Finite state machine is a very useful design model, it can be used to simulate many events in the world. In short, finite state machine has three features: Number of states is finite At any moment, one object can only be in one state In some condition, it will transfer from one state to another state In JavaScript, finite state machine can be applied in many places. For example, one menu element on a webpage. When the mouse hovers on the menu, the menu will show up, while the mouse moves away...

   JavaScript,Finite state machine,State     2013-09-02 11:00:57

  Guide on recovering data in MySQL

In our daily work, there might be mistakes made which got some data or even databases deleted in MySQL. If this happens on production, it would be a nightmare. In case this happens, normally DBA would jump in to save the world. And they would try to recover the data from the backup if there is any. But if there is no backup, then the show stops. Hence database backup is necessary on production environments to avoid such awkward situation. Also normally in MySQL, binlog should be enabled as well ...

   MYSQL,DATABASE,BACKUP,BINLOG,EXAMPLE     2020-08-26 07:50:30

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