The root account is the most privileged account on a Unix system. The root account has no security restrictions imposed upon it (Hmm…there are some exceptions though). When you are logged in as super user, you don’t have to face any questions. Therefore it is easy, with a mistyped command, to wipe out crucial system files or even the whole system all of a sudden. I have had situations where I forgot my root password and is unable to do any administrative level tasks. Due to increase in different type of cloud services, users are forced to manage large number of passwords and it is very common to forget some of them which may include the system’s own root password. What can we do in those situations? Either we recover or just reset the previous root password with a new one. The former is Read More »
Compiling Linux kernel with Rich ACL support
I don’t know how many of you have heard about Rich ACL or Rich Access Control Lists. Most of you might have heard about NFS protocol i.e, the Network File System protocol. This particular protocol, with its v4.0 and above defines a particular set of ACLS known as NFSv4 ACLs. Rich ACL is a modified or an extended form of NFSv4 ACLs. Let me explain in brief on what do we mean by ACLs.
ACL or Access Control List ?
This is a list of permissions attached to an object. The object can be file, directories and so on. An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects.
ACLs and Linux
Linux follows the POSIX 1003.1e draft 17 standard for defining and storing ACLs. Even then in linux, getfacl and setfacl command line utilities do not strictly follow POSIX 1003.2c draft 17, which shows mostly in the way they handle default ACLs. For detailed explanation on how ACLs are defined and how they work in linux, please see http://users.suse.com/~agruen/acl/linux-acls/online/ .
Variations in ACL implementations
The ACL model implemented by the various versions of Windows is more powerful and complex than POSIX ACLs, and differs in several aspects. These differences create interoperability problems on both sides which is a disadvantage for UNIX-like systems. To address this issue, several UNIX-like systems started to support additional ACL models based on version 4 of the the Network File System (NFSv4) protocol specification. Linux is lacking this support so far. Following are some of the differences between various ACLs
Virtual classroom by sharing terminal over ssh using screen
In today’s world, all learning methods are based on remote locations. Considering the case with GNU/Linux, remote learning on topics like System Administration, Networking etc involves the execution of different commands from shell. Mere writing these commands in a tutorial sheet and passing it over does not make sense. Then what else we can do? Good question. Take an example of a Mathematics classroom. There students could see what are the different steps that teacher is performing inorder to solve various problems via white board/black board. Here this board will be placed in a position to be seen by everyone inside the classroom. How can we make use of the SCREEN tool in the light of above mentioned example?
What is screen?
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