Since I like to learn more about scripting, I decided to write my own SSH bruteforce prevention script instead of installing a plug-and-play tool. You can run the script manually or have it run every hour or so using crontab. As root, create a new directory for the script and files, name it for example […]

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 […]

I just had a server on which I was not able to start MySQL. The MySQL error log shows the following: 121121 18:30:13 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql 121121 18:30:13 [Note] Plugin ‘FEDERATED’ is disabled. 121121 18:30:13  InnoDB: Initializing buffer pool, size = 8.0M 121121 18:30:13  InnoDB: Completed initialization of buffer pool […]

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 […]

You can use iostat to find out disk utilization, but with iotop you can monitor the actual read/write. iotop watches the I/O usage information output by the kernel and displays it in a table of current I/O usage by processes. iotop syntax for monitoring I/O usage -o Will only show processes or threads which are […]

I am running Postfix on my Debian Linux server and using spamassassin to detect spam e-mails. However sometimes you just want to block all incoming e-mail from a domain name or e-mail address. With option ‘blacklist_from‘ in spamassassin this is very simple and useful. Locate your spamassassin configuration file and open it with your text […]

When you see the following error message it means that the PHP script is exceeding the memory limit which is set for PHP. Fatal error: Allowed memory size of xx bytes exhausted (tried to allocate xx bytes) in /path/to/script.php To change the memory limit for one specific script, add the following line at the top […]

I wrote a simple bash script to monitor the server load, once the server load reaches the threshold it will send out an e-mail. Once you have received an e-mail from this monitoring script, you have to reset the $fileCHECK file to ‘0’: # echo ‘0’ >  $fileCHECK # In this example script it should […]

Since a couple of days I have seen the following message on (CentOS) servers: WARNING: mismatch_cnt is not 0 on /dev/md1 I have Googled some around, posted on forums, but couldn’t find the cause of this. Anyways, I managed to fix it with a workaround: # echo repair >/sys/block/md1/md/sync_action # wait a bit …. # echo […]

Today I had some problems with setting up the network in Ubuntu. Restarting the network resulted in the following error message: # /etc/init.d/networking restart * Running /etc/init.d/networking restart is deprecated because it may not enable again some interfaces * Reconfiguring network interfaces… /etc/network/if-up.d/upstart: 43: cannot create /run/network/ifup.eth0: Directory nonexistent run-parts: /etc/network/if-up.d/upstart exited with return code […]