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Skip to content Brandon Checketts Web Programming, Linux System Administation, and Entrepreneurship in Athens Georgia Menu Configuring a Bitcoin Antminer S9 to Run Only part of the Day During Non-Peak Hours I’ve started tinkering with Bitcoin Mining. Power usage is the single largest cost, so you need ensure that you are using the absolute least expensive power in order to generate as much profit as possible. I live in Georgia and subscribe to Georgia Power’s ‘Smart Usage’ program , which has lower costs most of the time, but peak periods which are Mondays-Fridays in June-September between 2pm and 7pm have a much higher power cost. My full calculation puts the non-peak price per kWh at about $0.048 and peak prices at about three times higher at $0.151 per kWh. Mining bitcoin on an Antminer S9 is mildly profitable at the non-peak price, but definitely loses money at the peak price. Since it runs on a 220v plug, I can’t use something off-the-shelf like a smart plug to turn it on and off. I’m a linux geek anyway and would rather do it with software. The Antminer has a very bare-bones Linux OS, but it fortunately has crond installed, even though it is not running. These steps will enable crond and create a cron job that kills the bmminer process during the peak hours. It then reboots when the peak period is ending and starts everything back up. Note that the machine is still on with fans running. It just doesn’t run the mining process which consumes all of the power. You can see my power usage in the chart below, showing that power usage dropped significantly during the time from 2pm-7pm. Here is how to make it work: SSH into the Antminer. Default user is root , password of admin ssh root@192.168.1.200 Have it start cron at boot by adding this line to the bottom of /etc/inittab: echo "cron:2345:once:/usr/sbin/crond" >> /etc/inittab mkdir /var/spool/cron/crontabs Run crontab -e to edit the root crontab in vi Paste in this content, modify for your desired time times. Note that times are in Universal Coordinated Time (UTC) ## Here we will stop `single-board-test` and `bmminer` from running during "Peak" periods for Georgia Power ## when it is unprofitable to mine due to increase in power cost ## 'Peak' is defined as 2pm-7pm, Monday-Friday, in June-September ## Since monitorcg is started from inittab and can't effectively be killed, we kill single-board-test and bmminer every minute ## during the peak hours ## kill `single-board-test`, which monitors and restarts `bmminer` * 18-22 * 6-9 1-5 /bin/kill `/bin/ps -ef | /bin/grep single-board | /bin/grep -v grep | /usr/bin/head -n1 | /usr/bin/cut -c1-5` ## Also, obviously kill `bmminer` * 18-22 * 6-9 1-5 /bin/kill `/bin/ps -ef | /bin/grep bmminer | /bin/grep -v grep | /usr/bin/head -n1 | /usr/bin/cut -c1-5` ## Reboot at 6:59pm EDT, which will restart the whole machine, bmminer with it (and takes a few minutes to start back up) 59 22 * 6-9 1-5 /sbin/reboot Exit vi with saving by typing<ESC> :wq <ENTER> Finally, just type reboot at the command line to have the machine restart. Author Brandon Posted on September 17, 2018 September 17, 2018 Categories General 3 Comments on Configuring a Bitcoin Antminer S9 to Run Only part of the Day During Non-Peak Hours PHP Sessions with Redis Cluster (using AWS Elasticache) I’ve recently been moving some of our project from a single Redis server (or server with a replica) to the more modern Redis Cluster configuration. However, when trying to set up PHP sessions to use the cluster, I found there wasn’t a lot of documentation or examples. This serves as a walk-through for setting up PHP sessions to use a redis Cluster, specifically with Elasticache on AWS. First, create your Elasticache Redis Instance like so. Note the “Cluster Mode Enabled” is what causes redis to operate in Cluster mode. Once there servers are launched, make note of the Configuration Endpoint which should look something like: my-redis-server.dltwen.clustercfg.usw1.cache.amazonaws.com:6379 Finally, use these settings in your php.ini file. The exact location of this file will depend on your OS, but on modern Ubuntu instances, You can place it in /etc/php/7.0/apache2/conf.d/30-redis-sessions.ini Note the special syntax for the save_path where is has seed[]= . You only need to put the main cluster configuration endpoint here. Not all of the individual instances as other examples online appear to use. session.save_handler = rediscluster session.save_path = "seed[]=my-redis-server.dltwen.clustercfg.usw1.cache.amazonaws.com:6379" session.gc_maxlifetime = 1296000 That’s it. Restart your webserver and sessions should now get saved to your Redis cluster. IIn the even that something goes wrong, you might see something like this in your web server log files: PHP Warning: Unknown: Failed to write session data (redis). Please verify that the current setting of session.save_path is correct (tcp://my-redis-server.dltwen.clustercfg.use1.cache.amazonaws.com:6379) in Unknown on line 0 Author Brandon Posted on September 26, 2017 September 26, 2017 Categories Linux System Administration , PHP , Programming 2 Comments on PHP Sessions with Redis Cluster (using AWS Elasticache) MySQL Statistics for Updates/Inserts per-table For a long time, I’ve never been able to answer some basic questions that I thought fundamental to optimizing server performance. MySQL gives you some server-wide metrics about activity, but none of it is broken down per-table so that an application developer could look into where to reduce the number of writes, or generally where to focus their attention in order to improve the server performance. I finally got ambitious enough to tackle this problem and asked a question on StackOverflow at http://stackoverflow.com/questions/39459185/mysql-how-to-count-the-number-of-inserts-updates-to-a-table A commenter named barat pointed me to this post which had the insightful idea of parsing the binary log for analysis. Since my servers are generally hosted on AWS, I don’t have direct access to the binary log, so I had to retrieve those. The MySQL documentation for the mysqlbinlog command briefly mentions how to read the binary log from a remote server. It took some experimentation to get the right command and output options with all of the data I wanted. Specifically, the `–base64-output=DECODE-ROWS –verbose` options which translate some of the row-based logging into MySQL commands that can be parsed. The first step is to create a user that has access to the binary logs. I used the main ‘admin’ user that RDS creates because it was convenient. If creating a new user, you probably need to grant the REPLICATION_SLAVE privilege. You can see which binary logs are available on the server with the SHOW BINARY LOGS; command: mysql> show binary logs; +----------------------------+-----------+ | Log_name | File_size | +----------------------------+-----------+ | mysql-bin-changelog.232522 | 16943219 | | mysql-bin-changelog.232523 | 32300889 | | mysql-bin-changelog.232524 | 15470603 | +----------------------------+-----------+ Then you can actually retrieve the log and print to STDOUT using this command: 14:01 $ mysqlbinlog --read-from-remote-server \ --host myhost.somerandomchars.us-east-1.rds.amazonaws.com \ --user admin \ --password="mypassword" mysql-bin-changelog.232522 Note that if you get the error below, you need to make sure that your MySQL client and server tools are using the same version. I originally attempted to use MySQL 5.5 tools with a MySQL 5.6 server. ERROR: Got error reading packet from server: Slave can not handle replication events with the checksum that master is configured to log; the first event 'mysql-bin-changelog.232519' at 4, the last event read from '/rdsdbdata/log/binlog/mysql-bin-changelog.232519' at 120, the last byte read from '/rdsdbdata/log/binlog/mysql-bin-changelog.232519' at 120. After that, it was just a matter of parsing the file for the relevant commands. I’ve put all of th...