Add systemd Startup Script For CouchDB

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Add systemd Startup Script For CouchDB

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couchdb-whiteCurrently, version 2.0 of CouchDB doesn’t come with any form of startup script. I’m sure that as the CouchDB 2 branch becomes more mature and it’s added to the various software repositories startup scripts will be shipped as standard, but until then we have to make do.

The below script is a systemd startup script with a cat command to create the file with the required content in the systemd config directories. Run the below script to create the startup file. You’ll need to change /usr/bin/couchdb to be the location of your couchdb executable.

You’ll then need to reload the systemd daemon and add the couchdb service to the startup routine. Run the below commands to enable CouchDB at machine startup.

 


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Manually downloading Java For Use With Webupd8’s apt-get Package

Category : How-to

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java-logoOracle Java is one of the biggest problems in life. That’s just a fact. Half of it is the fact that you have to download it directly from Oracle each time, quarter of it is the almost daily updates (compounded by the first problem), and the remainder is dealing with the fact that the first problem is there by design.

Thankfully the boys and girls over at Webupd8 have created and maintain an apt-get deployed version of Oracle Java that handles initial setup and future updates. The apt package doesn’t actually contain the Oracle Java binaries, because that’s against Oracle’s TOC’s, but it contains a script that downloads it for you – all behind the scenes.

Sometimes Corporate networks block access to Oracle’s download servers and therefore block access to you installing Oracle Java by this method. Except…

You can manually download the JDK from Oracle and copy it to the required machine in the apt cache directory. When you then run the apt-get command the installer will realise that the tar.gz containing the Java binaries is available and won’t need to download it. You’ll still need the internet to download the apt package, but you won’t need to access oracle.com.

First off, make the relevant cache directory for use with your version of java. This example assumes Java 8.

Copy the latest version of Java into the above cache directory. This assumes that the download is in your current directory and is Java version 8 update 91.

Finally install the required version of Java.

You’ll see the message Installing from local file as part of the installation indicating the installer hasn’t needed to download the Java binaries from Oracle.

 


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Install DataStax Cassandra 3 on Debain/ Ubuntu

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datastax-logoThe following process will install the DataStax distribution of Cassandra on any Debian based system, such as Debian or Ubuntu. We’ll use the official DataStax apt repositories to install Cassandra using apt-get.

Cassandra is written in Java and the latest version (at the time of writing) of Cassandra requires Java 8. You can use either OpenJDK or visit my Oracle Java post on installing the Oracle distribution of Java 8.

Once you have Java 8 installed and confirmed you can continue to install Cassandra. Use java -version on the command line to check your Java version.

Install DataStax Cassandra 3.4

Note: You can use the simple Bash script to install Java 8 and a single instance of Cassandra found here.

The first step to installing Cassandra with apt is to add the DataStax Cassandra repository and repository key to your local apt list. Run the following command to add the required repository and update your local apt cache. Change the version 3.4 on the first line to match the version you’d like to install.

Once you’re updated then run the install command and begin the Cassandra install.

Debian’s policy is for software to be available locally after the install has completed and therefore your Cassandra instance will be running as a single stand alone node.

You can run the nodetool to check the install has completed and that the Cassandra instance is available.

The next step is to configure your Cassandra instance by editing the yaml config file /etc/cassandra/cassandra.yaml but that’s a blog post for another day.


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Automated Bash MongoDB 3.2 Install Script for Debian/ Ubuntu

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mongodb-logoMongoDB is one of the leading noSQL breeds of database that’s been growing in popularity in recent years. The database is available in a ‘community edition’ that’s available for all to use freely.

The database setup and install is mostly straightforward however there are a few steps you have to take to get a MongoDB instance up and running.

The binaries aren’t shipped by the common Linux distributions so you’ll need to add the apt repositories hosted by mongodb.org. After installing the binaries there are a few config options that can be helpful to start with that are not contained in the default MongoDB install.

First off, create a file on your server called install_mongo.sh and copy the content of the script into it found in the below link.

MongoDB 3.2 Bash Install Script

Then make the script executable and run it.

Once the script completes you’ll be able to connect to your MongoDB instance with adminadmin.

What the MongoDB install script does

The following is a brief outline of the steps the script takes:

  1. Add the apt repository from mongodb.org and associated key.
  2. Install the full mongo-org package containing these packages: mongodb-org-server, mongodb-org-mongos, mongodb-org-shell, mongodb-org-tools.
  3.  Add a basic config file that:
    1. Enforces the wiredTiger storage engine.
    2. Enables remote access by listening on ALL interfaces.
    3. Enables replication, even if it’s just a stand alone node.
    4. Enables user authentication.
  4. Initiates the server as a replication cluster.
  5. Adds a user for administration called admin with password admin.

 


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Use DD to Quickly Benchmark Your CPU

Category : How-to

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Let me start by saying… this is a quick and dirty method and shouldn’t be used for precise comparisons of CPU performance. That said, it’s perfectly adequate for approximating CPU performance, especially on Cloud hosted VPSs to ensure you’re getting the horsepower that you’re being promised.

The idea here is to force your machine to perform tasks that will be computationally expensive to force your CPU to work at 100 percent and become the bottleneck for the task (rather than disk I/ O, etc.). This task will then be timed. The shorter times will generally represent faster CPU’s and longer results would indicate a slower CPU.

CPU benchmark

The md5sum command is a tool that creates an MD5 hash of some data. We can generate some data on the fly with dd and pipe it into the md5sum tool to create a computationally expensive task. We’ll limit the data to hash and time the length of time it takes to create the hash.

Run the below to start the test. If your result completes in under 2 seconds then increase the count=1k value to a higher value, for example count=10k.

You’ll get an output similar to the below output.

There are a couple of items that you’re interested in here, and the rest can be ignored.

  • 2.38909 s is the time it took in seconds for the operation to complete. This is the number to use for comparison with other machines – lower is better.
  • 449 MB/s is the speed that the data was fabricated and push into the md5sum tool to be hashed – higher is better.

 

CPU details with cpuinfo

Linux has various nuggets of information about your system available in the proc directory on a linux root partition. You can cat various files, such as /proc/cpuinfo, to see system specifications and metrics.

The output will look similar to the below output that shows a Xeon CPU running at a clock speed of 2.50GHz.

 


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Use A File As A Linux Block Device

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Just like when creating a SWAP file, you can create a file on a disk and present it as a block device. The block device would have a maximum file size of the backing file, and (as long as it’s not in use) be moved around like a normal file. For example, I could create a 1GB file on the filesystem and make Linux treat the file as a disk mounted in /dev/. And guess what – that’s what we’re going to do.

Create a file and filesystem to use as a block device

First off, use dd to create a 1GB file on an existing disk that we’ll use for our storage device:

Then ‘format’ the file to give it the structure of a filesystem. For this example we’re going to use ext4 but you could choose any filesystem that meets your needs.

You’ll be promoted with Proceed anyway?. Type y and press return to proceed with the process.

Mounting a loop device

Before mounting the file we need to check that there is a free /dev/loopX loopback device that we can use to represent our new block device.

Run the below command, and if there is any output then check if it’s one of your loop devices, which will more than likely reference /dev/loop as the mounted device. If you do have a reference to our loop device then see the below section on Unmounting a loop device, or choose a number higher than the highest listed loop device, for example: usually there are several loop devices, starting with loop0 and going up in value to loop1loop2, and so on.

Once you have the file that you’d like to mount and a free loop device then you can go ahead and mount the file as a block device. You have two options:

  1. Mount the file as a block device only
  2. Mount the file as a block device and mount the filesystem of it on a local mount point (eg. /mnt/mymountpoint).

For option 1; to only mount the file as a device in /dev/, run the below command and change /root/diskimage to the path of the file you’d like to mount. loop0 can also be incremented as explained above.

If you’d like this to be remounted after a machine reboot then add the above line to the rc.local file.

And add:

 

For option 2; to mount the file and the filesystem on it, use the mount command. You must have already created the mount point locally before running the command, as you would when mounting a disk or NFS share.

Then run the mount command and specify the loop device, the path of the file and the path to mount the filesystem on:

To check the file has been mounted you can use the df command:

Unmounting a loop device

If you’ve mounted the filesystem on the block device using the mount command then make sure it’s unmounted before proceeding.

To then free the loop0 device (or which ever loop device you’ve used) you’ll need the losetup command with the d switch.