Author: spectre

QEMU/KVM: Changing the default connect URI in libvirt

All the libvirt related commands, like virsh, virt-viewer or virt-install take a connect URI as parameter. The connect URI can be thought as specifying which set of virtual machines you want to control with that command, which physical machine to control, and how.

For example:

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virsh --connect "qemu+ssh://super@servers.arcade.click" start node011

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Supervisord: php script as pseudo-daemon

If and when you need to run a certain php script as a kind of daemon program, you can use the popular supervisord software package for this purpose.
Very often this will work much better, more efficiently and more conveniently as a replacement for clumsy php scripts in the system cron. Run the application in a short cycle, set the counter of time and repetitions – you’re done!

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CF: cf-cache-status headers explanation

When we are using Cloudflare in proxy mode, we see that the response headers contain invaluable information by lending insight into what’s really going on with our static object on pages.
This notice is small reminedr about the specifics of the cf-cache-status header, what its values mean.
It is very important in situations when you are making changes of css or js files and don’t see updates in window of browser, even if you are using suffixes for each URL.

When we work on site in production mode, each static object passthrough 3 level of caches before participation in rendering of page in browser:

  • cache plugin of WP(W3TC etc)
  • external caches of edge servers CF
  • local cache web browsers of clients

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Creating Users in MySQL and Percona 8 – caching_sha2_password error.

If you’ve started using MySQL 8, you’ll notice your usually commands for creating a user no longer function. That’s because it’s changed in MySQL 8, you need to now create a user, then grant privileges.

Let’s create a user:

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CREATE USER ‘newuser’@’localhost’ IDENTIFIED WITH mysql_native_password BY ‘user_password’;

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CentoOS openssl: Create a self-signed ECC certificate

Self-signed certificates and Elliptic Curve Cryptography

There are many reasons to self-sign SSL certificates, but we find them particularly useful for staging sites and in the early stages of a project. We have a three command guide to self-signing an SSL certificate if you aren’t interested in ECC.

If you also are interested in ECC, you may know that the main reason for using elliptic curves as the basis for communication over SSL is the small key size – where regular DSA would require 1024 bits, ECDSA (the elliptic-curve variant of DSA) would require about 160 bits. The computational power required for communication over ECDSA is also less.

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