I have developers come to me occasionally mystified by this error messages like this: ERROR 1055 (42000): ‘<tablename>.<columnname>’ isn’t in GROUP BY What does that mean, exactly, and why is the query getting kicked back? To illustrate, let’s say we have a tabe, geodata, which has this data for all US cities–the table has just ..
Category : Documentation
This is a step-by-step tutorial to install Python and Jupyter Notebook to Windows 10 (64 bit). Python 3.3 or greater, or Python 2.7 is required to install the Jupyter Notebook. Download Python 3.7.4 from “https://www.python.org/downloads/release/python-374/” url 2. Choose and select “x86–64 executable installer” for Windows 10–64 bit computer 3. Select location to save the executable ..
How to Install Kubernetes on CentOS 7 (Step by Step) Introduction Small virtual environments, called containers, have become indispensable for developing and managing applications. Working on applications within an isolated container does not affect the host operating system. Containers are more efficient than virtual machines as they do not need their operating system. Kubernetes is ..
Web based management interface for ProxySQL: https://proxyweb.org https://github.com/edmodo/proxyw..
MySQL 8.x not only requires that the datadir be empty when initializing, but also the directory designated as the temp directory. If the temp directory is not empty, the –initialize flag will not throw an error as it does if the datadir isn’t clean; rather, it will cause a “Data Dictionary initialization failed” message on ..
The screen utility is not included on some server builds. You *have* to have screen or tmux as a DBA or long-running scripts and DML will timeout and the ssh daemon will boot you off the server. As a workaround, I copy the “screen” binary from /usr/bin/screen on a server that does have it installed ..
Using an old cellphone as a portable PC system monitor:..
IPhone ..
www.dell.com/community/Laptops-General-Read-Only/I-need-to-replace-the-hard-drive-on-my-Inspiron-17R-N7110-HELP/td..
WebDAV client programs tested with FileRun: Program Name Operating System License Notes Windows Explorer Windows Our opinion: only if you don’t have other options MacOS Finder Mac Our opinion: decent solution Linux Linux Cyberduck Windows Mac Free Our opinion: decent solution WebDrive Windows Mac Free Trial Our opinion: very good! NetDrive Windows Mac Free Trial ..
If you have a Gmail account, you can configure your MTA to relay outgoing mail through Gmail. This gives you the benefit of Gmail’s reliability and robust infrastructure, and provides you with a simple means of sending email from the command line. In this tutorial, we will use Postfix as our MTA. Postfix is a ..
A sample service check, annotated: host_name dbsrp2076 <– name of server service_description SSH <– service being monitored servicegroups PROD-ssh <– service groups is_volatile 0 <– Does this service spontaneously start and stop (always 0 for “no”) check_period 24×7 <– during what hours is this service checked? max_check_attempts 10 <– ..
MySQL_LoadBalancer_Compa..
What if Windows let you quickly access administrative tools, backup and restore options and other important management settings from a single window? If that sounds good, look no further than the so-called “God Mode.” What Is God Mode? No, God Mode doesn’t unlock any extra secret features in Windows or let you do any tweaking ..
At times it is necessary to repair TCP/IP stack because the links between the layers may become broken. When you try pinging an address, you get a response but still cannot connect to your network or the internet. Start > All Programs > Accessories and right click on “Command Prompt”, select “Run as Administrator” to ..
From screentogif.com: This free tool was (and still is) mainly projected to work as a quick and small screen recorder. If you plan to record hours of fullscreen content, I recommend switching to more advanced software. Recording 📹 ScreenToGif allows you to record part of your screen with the Screen Recorder, also there’s the Webcam ..
Nikto is a very popular and easy to use webserver assessment tool to find potential problems and vulnerabilities very quickly. This tutorial shows you how to scan webservers for vulnerabilities using Nikto in Kali Linux. Nikto comes standard as a tool with Kali Linux and should be your first choice when pen testing webservers and web applications. ..
MySQL 5.7 was the last entry into the MySQL world before 8.x, and it added a dependable multi-threaded replication applier. This article will focus on the performance of the multi-threaded slave applier (MTS), and about its scalability in particular. For those in a hurry, here is a summary of what follows: The multi-threaded applier can ..
To view the existing routes, C:\> route print To add a static route, Syntax: C:\> route add <target> mask <netmask> <gateway IP> metric <metric cost> if <interface> Example: C:\> route add 10.10.10.0 mask 255.255.255.0 192.168.1.1 metric 1 Note: If there is more than one Network Interface and if the interface is not mentioned, the interface ..
Action Arch Red Hat/Fedora Debian/Ubuntu SUSE/openSUSE Gentoo Install a package(s) by name pacman -S yum install apt-get install zypper install zypper in emerge [-a] Remove a package(s) by name pacman -Rs yum remove/erase apt-get autoremove zypper remove zypper rm emerge -C Search for package(s) by searching the expression in name, description, short description. What exact ..
Tomcat–not my favorite. General Steps Create a Key and Certificate Request Issue the Certificate from your favorite Registrar Merge the Certificate into a Tomcat File Create a Key and Certificate Request On your favorite Linux or Windows box, make sure you have OpenSSL. I am making a directory called /home/keystore. Seems fitting. So: mkdir ..
Executive Summary Advice is seldom welcome. And those who want it most always like it the least. Philip Dormer Stanhope, Earl of Chesterfield (1694-1773) Guiding philosophy of this document: The hero isn’t the developer that battles problems through the weekend, but the one that avoided the problem. Best practices (BP in this document) ..
Some time in your life you’ll run across an Apache server that always has tons of TIME_WAIT connections just seeming to hang out. While these don’t take up as many resources as an ESTABLISHED connection, why keep them around so long? This short article will show you how to identify how many you have, and ..
The “last packet successfully received from the server XXXXX milliseconds ago” errors are virtually always caused by stale connections. There are a number of possible solutions, most having to do with small code changes. Here are things to try to alleviate the issue. I apologize in advance if these have already been tried; I’m shooting ..
Using the AWS console. Login to the AWS Management Console. Navigate to Redshift dashboard at https://console.aws.amazon.com/redshift/. In the left navigation panel, under Redshift Dashboard, click Clusters. Click Launch Cluster button from the dashboard top menu to start the cluster setup process. On the Cluster Details configuration page, enter a unique name for your new cluster ..
Original: How to set up WebDAV hosting on Apache – TechRepublic. WebDAV (Web-based Distributed Authoring and Versioning) is a way to share files over HTTP, much like you would use Samba or NFS. It has more limitations, and less speed, than filesystems like Samba or NFS, but with the proliferation of web servers and the ..
If you, or your clients, are unable to login to your/their email accounts and the system shows this error message: Plaintext authentication disallowed on non-secure (SSL/TLS) connections If you do not want to use SSL/TLS connection to get your email, and to disable SSL/TLS secure connection, do the following: 1. Edit dovecot configuration file: /etc/dovecot.conf ..
Original: How to set up WebDAV hosting on Apache – TechRepublic. WebDAV (Web-based Distributed Authoring and Versioning) is a way to share files over HTTP, much like you would use Samba or NFS. It has more limitations, and less speed, than filesystems like Samba or NFS, but with the proliferation of web servers and the ..
Original: Negotiation: Discovered File(s) Matching Request: None Could Be Negotiated. Posted June 24, 2011 at 9:30 AM by Ben Nadel Yesterday, I lost at least two hours trying to figure out why my local copy of a website was throwing 404 (File Not Found) errors. We had just implemented some URL rewriting on the production ..
This howto page will provide instructions on how to reach services running inside a firewall from outside of the network by using the Putty SSH Client and SSH Port Tunneling. Requirements Download Putty.exe. Port Tunneling Launch Putty. Different categories will be listed on the left side, click on Connection > SSH > Tunnels. Under Add ..
By now, we’re all aware that a utf8 charset and collation is the “right” thing to do, with most folks opting for utf8_general_ci or utf8_unicode_ci. However, lots of installations still default to some form of latin1, which is unfortunate. There are multiple ways to do this, all which functionally do the same thing. Be aware ..
The Linux kernel provides a tweakable setting that controls how often the swap file is used, called swappiness. A swappiness setting of zero means that the disk will be avoided unless absolutely necessary (you run out of memory), while a swappiness setting of 100 means that programs will be swapped to disk almost instantly. Ubuntu ..
There are times when you need to move WordPress around within your server, and times when you need to move WordPress from one server to another. You don’t need to reinstall. WordPress is flexible enough to handle all of these situations. When Your Domain Name and URLs Do Not Change Moving your domain without changing ..
Many people want WordPress to power their site’s root (e.g. http://example.com) but they don’t want all of the WordPress files cluttering up their root directory. WordPress allows you to install it into a subdirectory, but have your blog exist in the site root. As of Version 3.5, Multisite users may use all of the functionality ..
Below is a fairly comprehensive list of most widely used performance testing tools for measuring web application performance and load stress capacity, current as of this post date (2012-09-19). These load testing tools will ensure your application performance in peak traffic and extreme stress conditions. The list includes open source as well as licensed performance ..
MySQL is SO irritating in its timestamp limitations, in that you can only have one default timestamp column. (Update 6/12/2013: in version 5.6.x, this restriction will be lifted, so I hear) However, you *can* trick MySQL like this. You can use only one of the definitions in one table. Create both timestamp columns like so: ..
CONVERT ALL THE THINGS. Well, almost all the things. #!/bin/bash for database in aaaaa bbbbb ccccc ddddd eeee do thesetables=`mysql -N -B -e “SELECT CONCAT(TABLE_SCHEMA,’.’,TABLE_NAME) \ FROM information_schema.TABLES where TABLE_SCHEMA = \”$database\”” \ AND TABLE_SCHEMA NOT IN (‘mysql’,’information_schema’,’performance_schema’)` alltables=`echo $alltables $thesetables` # change the schema itself mysql -e “ALTER DATABASE $database CHARACTER SET utf8 COLLATE ..
#!/usr/bin/perl # query the system through the generic sysctl(8) interface # (this does not require special priviledges) my $sysctl = {}; my $sysctl_output = `/sbin/sysctl -a`; foreach my $line (split(/n/, $sysctl_output)) { if ($line =~ m/^([^:]+):s+(.+)s*$/s) { $sysctl->{$1} = $2; } } # round the physical memory size to the next power of two which ..
NORMALIZATION DIAGRAM ACID Atomicity Transactions are often composed of multiple statements. Atomicity guarantees that each transaction is treated as a single “unit”, which either succeeds completely, or fails completely: if any of the statements constituting a transaction fails to complete, the entire transaction fails and the database is left unchanged. An atomic system must ..
These are online, self-guided ways for developers wishing to gain more RDBMS understanding (or have a refresher course) in the two most ubiquitous platforms — MySQL and PostgreSQL. I add and remove from this list from time to time as material becomes outdated or better bits are found. Disclaimer: I didn’t have a hand in ..
If ever there was a TL;DR, this is it. However, it is important to understand the “whys” in my world, so here goes. A full discussion of character sets and encoding is beyond the scope of this document. (If you want more background, I recommend checking out the wikipedia article for a good place to ..
(2012-05-12 update: Please replace all mentions of “utf8” with “utf8mb4” to get a full utf8 character set. utf8_general_ci is just a half-assed implementation of utf8. Similarly, replace all representations of utf8_xxxxxx_xx collations with their utf8mb4 variant. In for a penny, in for a pound. NO ONE wants to do two utf8 migrations, ever. The methodology ..