jmap: Could not reserve enough space for object heap
If you get the following error message when using jmap to get a Java heap dump: # $JAVA_HOME/bin/jmap -dump:file=/tmp/dump.hprof PID Error occurred during initialization of VM Could not reserve enough...
View ArticleLinux: Apache logs
Location The Apache Web Server log files contains all errors found while serving requests as well as records of all incoming requests. The location of the log files is configurable. By default they are...
View ArticleQmail: 30 to 60 seconds connection delay
I’ve noticed that when connection to port 25 of one of our servers, it took quite a long time until commands can be sent. To test it, zou connect using telnet> telnet xxx.xxx.xxx.xxx 25 Where...
View ArticleOptimize images on Linux and Mac
Most website have many images. You might not be aware of it but it does. I mostly have text and code in my posts and thought I do not need to care too much about optimizing the images in there because...
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Linux: Configure AIDE (Advanced Intrusion Detection Environment)
We upgraded our server to Debian Wheezy and Plesk 11.5 about a week ago and started getting many emails from cron. Luckily I had entered the email address of a colleague as administrator and he got the...
View ArticleLinux: keep track of command execution and its output
Just a short post about how you can keep track of the which commands you have executed as well as there output. This is especially useful when you want to document how you performed some task or solved...
View ArticleLinux: Simple incremental backup script
This is a simple script to perform an incremental backup of a directory. It will create a backup folder and in this folder it will create subfolders with a timestamp as name. Every file modified since...
View ArticleLinux: Execute previous command and replace program name
Sometimes you execute a command and need to execute it again by changing the program called e.g. cat /etc/hosts vi /etc/hosts Of course you can just use the arrow up to get back to the previous line,...
View ArticleLinux: Working with jobs
I’ve noticed that many people I work with and have to do something in a Linux shell tend to not use jobs much. I’m not too sure whether it’s because they do not know how to use them or because it isn’t...
View ArticleSybase ASE: check contents of the procedure cache
In order to peek into the procedure cache, you can use the following dbcc command: dbcc procbuf In order to see the output on the console, use: dbcc traceon(3604) go dbcc procbuf go You’ll see that the...
View ArticleHorde webmail showing the default Plesk page
After migrating all our domains to a new server, whenever you wanted to access emails using the Horde webmail UI, you’d see the default Plesk page instead of the Horde login page. Executing the...
View ArticleSVN: Subversion 1.8 on Debian 7 (Wheezy)
Debian 7 (Wheezy) is still only shipping with Subversion 1.6 (see Details of package subversion in wheezy). First you need to add the WANdisco GPG key to the apt sources keyring: $ wget -q...
View ArticleSwitching to user root
Why switch to root ? When in a shell as a non-root user, you have to use sudo to execute a command which requires root privileges e.g.: sudo chown henribenoit:_www * That’s the clean way of doing it:...
View ArticleDebian/Ubuntu: The following packages have been kept back
Note that for all commands below, you might need to add a leading sudo depending on your system. When updating your packages using apt-get, you might get the following message: # apt-get upgrade...
View ArticleDebian / Ubuntu: viewing the apt change log
I am running rkhunter as a cron job and thus receiving notification any time I’ve installed something. Ideally I should be checking the output immediately and updating its database if it is just...
View ArticleLinux: Check the glibc version
If you need to check which version of the GNU C library (glibc) is used on you Linux system, whether it’s to check whether you are affected by the GHOST vulnerability or you need to install a software...
View ArticleLinux: ls hangs after NFS connection issues
We noticed today that ls was hanging when run on a particular directory. It didn’t seem to matter which options were used. This directory was not any directory but a directory where NFS shares were...
View ArticleBlocking all BlazingFast IP address blocks (ranges)
Over the past few weeks, I’ve had some issues with my site sometimes not being available or loading very slowly. Checking on the server I could see a high number of Apache processes and a memory usage...
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