I had recently problems with servers running application server Java and suddenly began to see strange errors like “broken pipe” or exausted resources, this is often due to the high number of open files that a modern server can bind especially compared to the default Linux systems that is still standing at 1024.
Let’s see how many open files are present on our system and how to resolve, or better to prevent this problem.
Continue reading »
Many Java application server use a keystore as a repository of their certificates and in general all Java applications use the one supplied with the JDK itself, Let’s see what is it and how to work with it.
A keystore is a repository of security certificates, that can hold your keys and certificates and encrypt them all with a password. In other words, a keystore is just like a hashtable which has an alias that identifies a certificate and then the certificate itself.
The Java JDK maintains a CAC keystore in jre/lib/security/cacerts. JDKs provide a tool keytool to manipulate the keystore.
Another way to manage this kind of certificate is Portecle a graphical tool that can help in these operation.
Or scp VS tar+ssh VS rsync+ssh VS tar+netcat
In a previous article in which i’ve show some uses of tar, I made an example of how to use it to move large amounts of data between two computers, but many people have said that it is better, or at least they prefer to use rsync, others prefer to use netcat. I remain convinced that a tar+ssh is faster than rsync+ssh is correct then do a test on the field and see some numbers.
Continue reading »
In a previous article about the tar program I mentioned gzip and bzip2 compression methods as options to create a tarball (and I forgot xz).
To make amends today I will introduce the main methods to compress the file and I’ll do some tests to see how they behave.
I will consider zip, gzip, bzip2 and xv, i will not test compress another compression program present on Linux systems but now dated and surpassed by the other programs.
But as first thing an overview of these 4 methods/programs of compression
I recently had to move from one machine to another about 50 GB of data, divided into hundreds of thousands of small files, and i had no additional space on the machine to make a zipped tar and then move it comfortably, I tried a scp, but after 45 minutes it had moved around 2 GB of data, too slow.
And so I started looking at the options a bit more advanced of tar. Continue reading »