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  Use rsync to delete mass files quickly in Linux

Yesterday I encountered an issue to delete many log files in my Linux workstation, there were around 100,000 files to be deleted. These are log files and they grow very fast, and we need to delete them frequently. Usually we would use rm -rf * to delete these files, but we may need to wait for a relative long time if there are too many files. So we must adopt some unusual way. Fortunately, we can use rsync to delete mass files in one shot. 1. Install rsync yum install rsync 2. Create a new empty...

   rsync,delete file, demo     2012-11-13 10:44:50

  Check whether a remote server port is open on Linux

As a system administrator or network engineer or application developer, there is a need to check whether a port on remote server is open so that you can tell whether the service under check is running or not. In this post, we would cover a few methods to check whether a remote server port is open or not on Linux. telnet telnet is the most frequently used command on both Windows and Linux to check port. The simple usage for this command is  telnet [host] [port] When the port is open, the o...

   LINUX,TELNET,PORT,NC,NMAP     2017-12-23 11:45:20

  How to use xargs command in Linux

What is the xargs command? The xargs command constructs and executes commands provided through standard input. It takes input and converts it into command arguments for another command. This functionality is particularly useful in file management and can be combined with commands like rm, cp, mkdir, and others. Using the xargs command When used alone, the xargs command prompts the user to enter a text string and then passes it to the echo command. This example demonstrates the input provided an...

   XARGS,LINUX     2023-11-17 11:19:41

  Install Kubernetes with minikube and docker on Ubuntu

When someone just wants to play around Kubernetes on its local environment without accessing to Cloud provider resources, one can set Kubernetes up on local environment with minikube with single node mode. This post will provide a simple guideline on how to set up KUbernetes with minikube and docker on Ubuntu. Before all the steps can be started, you may need to first set up kubectl which is a command line tool to operate on Kubernetes resources. Post that, can ensure that docker is installed on...

   KUBERNETES,MINIKUBE,DOCKER,UBUNTU     2021-06-01 05:37:40

  Configure static IP for Linux

When a Linux server is running, it has to have an IP so that other machines can talk to it. It is often desired that the server would own a static IP so that every time other machines want to connect to it, the same IP address would be used. This is extremely useful when there are virtual machines installed on a host machine where the virtual machine would start and stop now and then.  To configure static IP address for a Linux server, the /etc/network/interfaces needs to be updated. Assumi...

   LINUX,NETWORK,STATIC IP,DNS     2017-07-08 08:39:58

  Maintain multiple versions of Go in one single environment

In a development environment, there might be multiple projects going on at the same time and they may require different development environments with different versions of build tool. In many programming languages, it is possible to have multiple versions of different build tool or development tool on a single environment. For example, there can be multiple JDKs, multiple versions of Ruby using RVM. For GoLang, there is a similar tool called GVM which can also be used to maintain multiple versio...

   GOLANG,GVM,GVM PKGSET,RVM     2019-11-10 00:43:47

  Create temp file in Bash using mktemp and trap

When working on Linux Bash, sometimes there is need to create temporary file. A common way of creating temp file on Linux is creating some file in /tmp directory. However there is security risk when creating temp file in /tmp directory. This post will show how to securely create temp file in Linux Bash. When creating file in /tmp directory, there are some security risks. This directory can be accessed by any user on the system, any user can write data into this directory as well. The files creat...

   LINUX,MKTEMP,TRAP,TEMP FILE     2019-12-30 23:28:23

  Using Java keytool programmatically

Java provides a command line tool to access and operate different keystore which store keys and certificates. This tool is named keytool and is located at \bin.  On command line, you can issue below command to generate a keystore named mytest.jks which contains a private key and certificate chain. keytool -genkeypair -alias mykey -keyalg RSA -sigalg SHA256withRSA -dname CN=Java -storetype JKS -keypass password -keystore mytest.jks -storepass password Sometimes, in testing purpose, w...

   JAVA,KEYTOOL     2016-01-09 06:28:07

  Something you may not know about Shell

Shell is also called command line interface, it is the interface between *nix users and computer. Shell is a program which provides service to access OS kernel services. This article is to introduce some not so well known but useful and interesting knowledge about shell. Wiki shell was born almost at the same time as Unix. The first UNIX shell was written by Ken Thompson in 1971 and its name is Thompson sh. It's older than Linux kernel. The default Shell in most *nix and MacOS is bash, bash was...

   Linux, Unix,Shell,Command     2012-11-24 07:19:47

  Linus Torvalds apologizes for Linux 4.8 kernel bug

On Oct 2, Linus Torvalds proudly announced the release of Linux 4.8. But just days after the release, a bug was found in the kernel and Linus came out and apologized for this bug. I'm really sorry I applied that last series from Andrew just before doing the 4.8 release, because they cause problems, and now it is in 4.8 (and that buggy crap is marked for stable too). In particular, I just got this kernel BUG at ./include/linux/swap.h:276 and the end result was a dea...

   LINUX,LINUX KERNEL,NEWS,LINUS TORVALDS,BUG_ON     2016-10-07 03:46:17

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