Sudo

There are cases sometimes where a non-root user needs to execute a command in Linux. Some of the commands like yum are not allowed to be executed by a non-root user. So whenever a non-root user tries to execute a command , a Permission exceptions is thrown. There is way in linux which allows executing a command by non-root user if he knows the root password. He can use the sudo command [oracle@localhost x86_64]$ sudo...

Read More

All You Need to Know about Class-loaders

Class-loaders in java play an important role in Java. They are the pieces that every java developer should be aware of. In this article we will see the working of a Class-loader in java. So what exactly is a Class-loader? Every class-loader is an Object. An Instance of the class that extends the abstract Class java.lang.ClassLoader....

Read More

Eclipse Memory Analyzer: Shallow heap and Retained heap

Developers are more concerned about the size of objects when they are created. Eclipse memory analyzer gives us information about the size of the object in 2 calculations. Shallow Heap Retained Heap Shallow heap is the memory consumed by one object. An object needs 32 or 64 bits (depending on the OS architecture) per reference, 4 bytes per Integer, 8 bytes per Long, etc. Depending on the heap dump format the size may...

Read More

Eclipse Memory Analyzer: Finding Strings

Eclipse Memory analyzer provides various ways of analyzing String from the heap dump. We can get the details of the String using 1. Open the Histogram -> Right Click on “java.lang.String” and select the List Objects. We can get the size by sorting the retained Size ( the memory kept alive by Each String ) 2. If we want to get...

Read More

Eclipse Memory Analyzer: Unreachable Objects

An Object becomes unreachable when they don’t have any inbound references or when they become unreachable from any other root. By default unreachable objects are removed from the heap dump which parsing and will not appear in the class histogram. We can still see the unreachable objects in Eclipse Memory analyzer. 1. From the link on the Overview page 2. From the Query Browser via Java Basics --> Unreachable Objects...

Read More

Find Local Variables in Eclipse Memory analyzer

Finding local variables from the heap dump generated is easy using eclipse memory analyzer. As we know the life of the local variable is very small but if the variable is alive during the time of heap generation, we can fine the local variable details using 1. Click on the objects options button from the actions bar   2....

Read More

Access Modes – setgid, setuid and Sticky bits

When ever we log into the system , a shell is started. While working there are many files that belong to many other users who have created them and we don’t have permissions to do any thing on this. Consider the case of a file /etc/passwd , this is a password file maintained by linux kernel for storing the user password. This file permission is set to change for only root user. So now consider when a different user want to...

Read More

Access Permissions

One of the important features that make a operating system good is Security. Linux is considered One of the secured Operating system. In this article we will see the basics of security in Linux. Normally in Linux we have 3 types of permissions that change the behavior of 3 entities. The 3 types of permissions are 'r'(Read ) : This allows you to read, view, or open a file 'w'(Write) : This allows you to edit or delete...

Read More