Author: Brandon (Page 13 of 29)

MySQL replication can be a bit fragile.  Most of the time replication fails when the slave tries to run an SQL statement that causes an error.   I’ve most frequently seen this when the slave is missing some table that I forgot to import when setting replication up.   Usually it is a simple enough job to create the table, then start the slave SQL thread again.

However, sometimes replication breaks for no particular reason at all. This morning, I had a slave stop because an invalid query somehow got written to the binary log.  I’m not quite sure how that happened, but fortunately I found a way to just skip the bad query.

mysql> stop slave;
Query OK, 0 rows affected (0.00 sec)

mysql> SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
Query OK, 0 rows affected (0.00 sec)

mysql> start slave;
Query OK, 0 rows affected (0.00 sec)

The ‘SQL_SLAVE_SKIP_COUNTER setting tells the slave SQL thread to skip that many queries when starting up. Note that you should really know what your database is doing and why it stopped before you just go running this command. It may cause your slave to get seriously out-of-sync with the master server.

Posts on this blog have been a little slow lately because I have been pretty busy with stuff in life.  For any family or friends, you can head on over to my family blog to read about what has been going on.

Whenever I create an SSL Certificate, I find myself going back and forth between several pages of notes.  I’m about to do this with a half-dozen certs that were generated on a Debian box with weak keys.  Here are the OpenSSL commands I find most useful:

Create a new key:

openssl genrsa -out MYDOMAIN.COM.key 2048

Remove the Pass Phrase from an existing key:

openssl rsa -in MYDOMAIN.COM.key.withpassword -out MYDOMAIN.COM.key

Create a Certificate Signing Request (CSR):

openssl req -new -key YOURDOMAIN.COM.key -out YOURDOMAIN.COM.csr

Inspect your CSR (or a previous one to copy values out of):

openssl req -noout -text -in MYDOMAIN.COM.csr

Self-Sign a Certificate

openssl x509 -req -days 3650 -in MYDOMAIN.COM.csr \
  -signkey MYDOMAIN.COM.key \
  -out MYDOMAIN.COM.crt

Inspect a certificate

openssl x509 -in MYDOMAIN.COM.crt -text | head -n 12

This command can be used to hibernate a Windows machine from some kind of script:

rundll32 powrprof.dll,SetSuspendState

I have found this useful in a couple situations. One is where I have a computer that I like to have on during the day, but not at night. I configured the Bios to turn the computer on automatically each day at a specified time. And then I used windows task scheduler to run the hibernate command at a specified time at night.

The other situation is some problem on one of my machines where it takes literally three or four minutes to bring up the shut down box after clicking start =>shutdown. Instead of doing that, I just created a shortcut on my desktop that runs the hibernate command and it does that immediately