Category: CentOS

Error: The monit service does not respond. Refer to Parallels technical support for help.

I have Plesk 12 installed on a machine running CentOS 6, but I am not able to start Watchdog due to the following error message: Error: The monit service does not respond. Refer to Parallels technical support for help. It seems that the monitrc template is using a log location which doesn’t exist and therefor […]

hpacucli not detecting HP Smart Array Controller

In some cases hpacucli is not detecting the HP Smart Array Controller, in my case it was a HP P420 controller. => ctrl all show Error: No controllers detected. => You can solve this issue by loading the sg module: # modprobe sg You’ll see now that the controller is detected: => ctrl all show […]

Solution for ip_conntrack: table full, dropping packet.

Today, I was working on a brand new  (apache) server, hosting a website with 3000 concurrent visitors. The load on the server was very low while the website was dropping network connections. I ran dmesg and the following message was repeating over and over: ip_conntrack: table full, dropping packet.   It seems that ip_conntrack keeps […]

Howto: RAID status on HP servers

Here is how you can view the status of your RAID configuration and the status of your physical drives. First we have to download and install the hpacucli tool. CentOS: # wget http://how2forge.info/files/hpacucli-8.60-8.0.noarch.rpm # rpm -ivh hpacucli-8.60-8.0.noarch.rpm Debian: # wget http://how2forge.info/files/hpacucli_8.60-8.0_i386.deb # dpkg -i hpacucli_8.60-8.0_i386.deb Once the tool is installed, start it: # hpacucli HP […]

Monitoring LSI RAID adapter with mpt-status

I have a few HP and Dell servers I manage that use LSI RAID controllers. To ensure remotely that a hard drive is not failed I was in need of a tool. I found the mpt-status utility, which is a tool for monitoring LSI RAID controllers. However, the installation took some time as I got […]

How to install PAE kernel on CentOS

When you have 4GB or more memory and you have a 32-bit kernel running, your machine will be limited to use around 3GB of memory. All you have to do is install PAE kernel package. 1. Install the PAE kernel package: # yum install kernel-PAE 2. Check your grub menu list, the ‘default’ value should […]

How to reset the MySQL root password

If you have forgotten the mysql root passwod, you can set a new password if you have root access to the server. 1. Stop MySQL server. # /etc/init.d/mysql stop 2. Start MySQL with –skip-grant-tables option. # mysqld_safe –skip-grant-tables & 3. Connect to MySQL as root. # mysql -u root 4. Set new mysql root password. […]

Upgrading CentOS to CentOS 5.6

CentOS 5.6 has been released on April 8th, 2011. If you are running CentOS 5.5 you can simply upgrade to CentOS 5.6 via yum by running: # yum update If upgrading from a version earlier than CentOS 5.5, it is advised to follow this procedure: # yum clean all # yum update glibc\* # yum […]

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