Jun 04 2020

Unable to load component class org.sonar.scanner.bootstrap.ScannerPluginInstaller

Suddenly “Error during SonarQube Scanner execution” began to appear during at the end of Jenkins build. The full text in Jenkins console output looks like this:

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May 26 2020

How to move disk space from LVM partition to another

Default LVM partitioning in Linux may not be optimal for some tasks. For example, root partition can be too small and filled up after some time while home partition is large and almost unused. In this case one obviously would want to transfer some amount of space from /home to / partitions.

Consider the following example: Continue reading

May 07 2020

Rescue a CentOS system with GRUB

GRUB (Grand Unified Bootloader)  is the most widely used bootloader among Linux operating systems (OS) but it can boot any OS.

GRUB main functionality is to allow users to select between different operating systems to boot. As bootloader GRUB is installed on the MBR (Master Boot Record) and additionally to allow us to select different OS it also allows us to select between different kernel or kernel parameters and to boot in rescue mode if our kernel was damaged or if we lost our root password as explained in a previous article in which on how to restore CentOS root password editing GRUB’s booting parameters. Continue reading

May 07 2020

CentOS / RHEL 7 : How to install kernel from rescue mode

troubleshooting option boot RHEL CentOS 7 into rescue modeA situation where the system has no kernel to boot from maybe because all the kernel are removed from the system or due to a corruption, Kernel installation from rescue mode is required. You can still install a new kernel from rescue mode and make the system up and be running again. Continue reading

May 06 2020

Inspecting and extracting Debian package contents

This post covers how to list and extract the contents of a Debian package. There will be examples used to show how to list the contents of debian packages that are installed and not-installed on a system, as well as, how to extract the debian control information and program files.

A debian package is a Unix ar archive that includes two tar archives: one containing the control information and another with the program data to be installed. Continue reading

May 06 2020

Inspecting and extracting RPM package contents

This article will cover basics of the RPM package architecture and show how we can see RPM package content and extract it. There will be examples how to extract RPM package files from Linux command line.

An RPM package is simply a header structure on top of a CPIO archive. The package itself is comprised of four sections: a header with a leading identifier (magic number) that identifies the file as an RPM package, a signature to verify the integrity of the package, the header or ‘tagged’ data containing package information, version numbers, and copyright messaging, and the archive containing the actual program files.

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Apr 27 2020

Recover WSFC and AlwaysOn from Resolving State

There is a SQL Server Availability Group (AG) on a Windows Server Failover Cluster (WSFC) with 3 nodes using Node Majority quorum configuration. In an unforeseen circumstance, 2 nodes went completely offline at the same time causing the WSFC to go down.

This caused the Availability Group to go into a Resolving state and all the databases in the AG and the AG Listener to be inaccessible. How to recover the WSFC cluster node to start without a quorum and later fully re-establish HA for AlwaysOn AG I’ll show below. Continue reading

Apr 22 2020

Disable send_redirects or NETKEY

disable-sendredirectsDuring the process of a VPN client configuration with xl2tpd and openswan ipsec verify command threw the following error:

Disable /proc/sys/net/ipv4/conf/*/send_redirects or NETKEY will act on or cause sending of bogus ICMP redirects!

To fix this we need to disable send_redirects and save changes in /etc/sysctl.conf so they will be permanent across reboots. Here is how: Continue reading

Apr 21 2020

Asterisk responds with 404 Not Found

Asterisk PBXWhile configuring SIP/PJSIP in Asterisk you may notice that Asterisk responds with 404 Not Found to the OPTIONS request. To demonstrate the behavior let’s have a look at this PJSIP debug log example: Continue reading

Apr 20 2020

Windows Allow Remote Desktop Login Without Password

When attempting to connect or establish Remote Desktop connection to a remote Windows XP, Windows Vista, Windows 7, Windows 8, Windows 8.1 or Windows 10 computer in order to remotely logon to the machine, the log on may be rejected with Remote Desktop client returns one of the following error messages: Continue reading

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