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Monthly Archives / February 2014

  • Feb 19 / 2014
  • 0
Linux

Create Software RAID under Linux system

A hard drive disk is a device with limits (performance, lifetime, …) and a broken disk often leads to a data loss, and sometimes with a loss of data more or less important.
In order to avoid that kind of inconvenience, there are several hardware solutions allowing disk replication, but most of time with a too high cost for a standard use (non professional). Fortunately, there is also a software RAID, which can be set up easily and quickly without any additional hardware (assuming you already own at least 2 hard drive disks) given that it’s working on a software layer between the hardware abstraction layer and the file system.

There are different levels of RAID ; the most common levels are:

  • RAID 0 : the “striping” allows to improve performance by splitting the IO requests on several devices in parallel (2 to n disks)
  • RAID 1 : the “mirroring” allows to write same data on several disks at the same time (to disks)
  • RAID 5 : the “striping and mirroring” allows the combination of RAID 0 and RAID 1 (3 to n disks)

I will present here how to set up a RAID 1 solution (mirroring) but it will be easy to adapt the following steps if you need another RAID level.

RAID 1 setup

For the setting up, ensure you have the mdadm package installed and ready on your system. For Debian/Ubuntu, you can use the following command:

Prepare both disks in Software Raid (type 0xfd) thanks to the fdisk tool:

You can now shrink and erase both disks with zeros thanks to the command below:

Create your RAID 1 (or any level, by changing the level attribute):

Format this new partition in ext4:

Mount your partition you just created:

To get an automatic mounting point after any restart of the system, edit the file /etc/fstab  and add this following line:

You can now check and follow your RAID status, by using following commands:

RAID Monitoring

To ensure the RAID is always working correctly and be informed when a disk is out of order, it is possible to set a monitoring solution thanks to the common tools of mdadm with a mail alert system.

Check that the monitoring settings are correctly defined in the file /etc/mdadm/mdadm.conf with the sender address (MAILFROM) and the receiver address (MAILADDR):

You will need a mail server enabled on your server (postfix, ssmtp, …) and listening on port 25.

To check and test this configuration, ou can easily perform a test by sending a mail report thanks to this command:

To ensure that monitoring is enabled for your RAID devices, just check that the –monitor option is correctly set by performing the following command:

If it’s not, you will have to add the option in the /etc/default/mdadm file (DAEMON_OPTIONS).

  • Feb 12 / 2014
  • 0
Linux

Add a Swap File

When you’re running on a Linux System (or any Unix Operating System), it’s common to use a swap to complete and optimize the memory usage on the computer (especially for older ones). There are different ways to do that, you can:

  • Create a swap on a full partition system (most of Linux distribution will allow you to create it when installing the system or later using fdisk commands to create partition and activate it by following the same steps than below from #2)
  • Create a swap file later on any partition and activate it directly using command-line

I will present here the second case: the creation of a swap file (you will need to get root rights to perform most of the following commands).

  1. Create a file with dd command to create a 1024MB empty file (which will be used by swap).

    We are here writing a file of 1024*1024MB=1048576 blocks size with a Read/Write of 1024 bytes at a time.
  2. Now format the file to swap format
  3. Ensure that the rights access are correct on this file (for security purposes)
  4. Now activate swap on your file
  5. To deactivate swap on your file, juste use the following command

You can now check your swap availability by using the top or free -m command.

Right now, you probably want this swap file to be mounted and activated automatically at the system startup to avoid to perform these steps manually each time ? No problem, juste edit the /etc/fstab file and add this following line:


Your system has now a swap file ready to use !

  • Feb 06 / 2014
  • 0
Google Chrome

Uninstall/Install manually Google Chrome

Sometimes, further to a problem, an automatic uninstall process of Chrome is not efficient. In that case, you will need to proceed with a manual uninstall. Here are the steps you can use to perform a safe reinstallation:

  1. Perform a Google Chrome uninstall as explained right here: https://support.google.com/chrome/answer/95319?hl=en
  2. Create a new Chrome user profile: https://support.google.com/chrome/answer/142059?hl=en
  3. Download file remove.zip (right click – Save as), save it on your desktop, unzip it and execute the remove.reg file to remove any Google Chrome entries in your Windows registry (you will probably need administrator rights for this step)
  4. Once you’ve performed all these steps, you can perform a fresh install of Google Chrome from the official website: https://www.google.com/chrome

You can now start again your favorite browser, and reconfigure it as you want (or simply connect to your Google Account and let the synchronization do it by itself …) !

Question ? Contact