Reset mySQL (mariadb) master/slave with GTID replication

To reset and start fresh, do;

Issue with slackpkg and gpg key

I found an issue while using slackpkg where the following error presented itself:

ERROR: Verification of the  gpg signature on CHECKSUMS.md5
               failed! This could mean that the file is out of date
               or has been tampered with. If you use mirrors.slackware.com
               as your mirror, this could also mean that the mirror to
               which you got redirected is not yet updated with the most
               recent changes in the Slackware tree.

An alternative way to use wget

Normally wget works as expected but every now and then, you page is forbidden or similar, so the below is an alternative approach;

Import certificate into Java keystore

The below example involves importing a Zscaler root CA certificate into the java keystore on my Slackware installation.

sudo keytool -import -trustcacerts -alias zscaler -file /etc/ssl/certs/Zscaler-Dalzell.crt -keystore /opt/jdk1.8.0_341/jre/lib/security/cacerts
 

Linux boot and shutdown times

 

To find the last boot time, can of course do w which will show us how long the system has been up, but to save the mental arithmetic, we can do:

who -b or uptime -s

To find the last shutdown time, we can do:

last -x | grep shutdown or last -x | grep reboot (output varies between distributions)

Information from SHOW SLAVE STATUS on mysql

SHOW SLAVE STATUS\G;

UEFI, EFI, elilo and Slackware

 I recently came across a system that would not allow me to use legacy boot, so...

Convert gamma system server to virtual box vm

 This is a work in progress...

Kill a process on OpenVMS

show system

stop/id=nnnn (where nnnn is the PID from the above command)

Restarting processes on Alpha

 

Reset Windows password

Reset Windows password

Adding a PATH variable on the Mac

We can modify the /etc/paths file or we can create a file under /etc/paths.d such as /etc/paths.d/docker

which could contain;

~/.docker/bin

where the docker bin was located at /Users/my_username/.docker/bin

See also [here] for an example of adding JAVA to the System PATH in Linux.

Install command line tools on Mac

xcode-select --install 

MySQL flush-hosts and ERROR 1129 (HY000)

Often we see an error such as:

ERROR 1129 (HY000): Host 'nn.nn.nn.nn' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'

SSH HostkeyAlgorithms

 A note for .ssh/config

Limit max number of characters in a java text field.

 

Java Method Overriding v Overloading

 I found this useful and interesting, especially as the terms are so easily mixed up (by me at least).

Nexus 5

Unlocking, rooting, installing a custom recovery, installing Kali and reverting my Nexus 5 back to stock.

Serial ports

Serial port pinouts

Fig's 1&2 show the more common 9 pin serial pinouts, on both the computer side and also the device side respectively. Fig.3 gives a more visual representation of the male variant, most commonly found non the PC side. I think this was historically due to a male being more prone to damage, hence the female end being more commonly used on cables, but I may be wrong.

Fig.5 is particularly useful when testing cables, although I have only really connected pints 2&3 for this purpose. The idea here is that you make a plug that connects the pins together and then you can open the port and whatever you type should be echoed back exactly. 

Fig's 6-10 provide details about Null Modem connectivity.

Fig.11 provides more pinout details for the DB25 connectors

Printing control characters

We can echo a control char as per the below;

echo -e '\x07'

The above will give us a BEL

if we want to add control characters to a file, we can do;

printf 'hello there \x07 my name is Snake' > test.txt

if we then cat test.txt, well see the text and a BEL

We can of course send this to a serial port with something like cat test.txt > /dev/ttyS0