Linux File System Continue …

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I discussed about lsof and ps(process status) commands in the  last blog post.   I strongly recommend you to read earlier blogs for better understanding . If you find something missing, Please provide feedback in comment box so that I can take corrective action.

I will be using redirection wherever it requires.

Redirection
  • >     Redirect output
  • >>   Redirect and append
  • <     Redirect input
  • <<  Redirect input and append
  •   Pipe
  • tee Redirect to two objects . You may think it as Tee used in plumbing

As we observed that the root filesystem itself has a number of utilities and libraries for supporting linux based applications. The next requirement is to understand the search options. The most frequently used commands are :

  • locate to find files or directories
    • locate test6
  • find to search file is more powerful if you are aware of options
    • find -type f -name test6     //Did you face any problem ? Try the command given below
    • find -type f -name test6 2>/dev/null
    • Did you notice the errors going to /dev/null  ? Like black hole
  • grep to search pattern in each file or standard input
    • Even if you use grep , You can’t avoid error messages without redirecting stderr to /dev/null
    • find -type f -name test6 | grep “day”
  • Please refer to man or help for any specific requirement with these commands
How can I create a Filesystem from scratch ?

Since Kernel takes care of resource management and the software architecture has flexibility to pick necessary utilities for Filesystem, There should be a method to design the entire filesystem from scratch. Following is the method to achieve the same :

  • One can use dd(Data Definition) and mke2fs to create an etx2 file system
sanjay@sanjay-VirtualBox:~/linux_day5$ dd if=/dev/zero of=myfile1.img bs=1024 count=102400
102400+0 records in
102400+0 records out
104857600 bytes (105 MB, 100 MiB) copied, 0.248331 s, 422 MB/s
sanjay@sanjay-VirtualBox:~/linux_day5$ mke2fs myfile1.img -
sudo mount myfile1.img tmp/ -o loop

If we create partition table in the file image above, It will become virtual hard disk image. Loop device is a pseudo device which makes a filesystem appear as a block device. After mounting the filesystem, we can copy the required files inside this.

As I discussed earlier /dev directory nodes provide device access to user space application . However there is another directory /sys which provides device configuration and status specific information.  /proc provides information related to kernel running status.

References

 

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