fsck is just the original name. When they came out with new file systems they would need a specific tool for each one, efsck for ext, e2fsck for ext2, dosfsck, fsckvfat. So they made fsck the front end that just calls whichever is the appropriate tool.
1. Directory structure
This should be covered in the Filesystem Hierarchy Standard
(2.3 PDF)
/bin/ Essential command binaries that need to be available in single user mode;
for all users, e.g., cat, ls, cp
/sbin/ Essential system binaries, e.g., init, ip, mount.
/usr/bin/ Non-essential command binaries (not needed in single user mode);
for all users
/usr/sbin/ Non-essential system binaries, e.g. daemons for various network-services.
/usr/local/ Tertiary hierarchy for local data, specific to this host.
Typically has further subdirectories, e.g., bin/, lib/, share/
2. Installation
I use a package manager wherever possible (e.g. yum or apt-get). This is possible for a very large number of applications, in a few cases you may have to add a repository. My second choice would be lower level packages such as RPMs and compiling from source would be my last resort (but some people prefer this)
Some package managers can install from RPMs (e.g. yum install oddity.rpm
)
If you are compiling from source, its probably not a huge step to create your own package so that the system installer knows what you've done.
Then your problem reduces to e.g. yum remove packagename
The alternative is to keep good documentation about all sysadmin activities undertaken (I keep a journal in a text file anyway)
Best Answer
The differences : man hier
It displays short and to the point information about almost every file/folder in the Linux File System Hierarchy. And for the files/folders you want to know, It says :
And for the file/folder /usr/lib/x86_64-linux-gnu, I (am not sure, but) think this :
Can I remove the duplicate so files ?
I'm not sure what exactly consequences may be of removing the duplicates but would advise not do so. Read this.
Hope you noticed read-only data and shareable.
Feel free to add in more details.