Skip to main content

Representation of File System in the Kernel

Representation of data on a floppy and hard disk may consistently differ, but representing them in the kernel is almost same.

VFS mounts the file system through the function

  • register_filesystem(struct file_system_type *fs),
  • Example

register_filesystem(&ext2_fs_type);

Mounting

  • Before a file can be accessed, the file system containing the file should be mounted.
  • Done by the call using mount or function mount_root()
  • Every mounted file system is represented by a super_block structure.
  • The function read_super()of the VFS is used to initialize the superblock
    • Managing the file system
    • Will issue some flags during the mounting like

MS_RDONLY //File system is read only

MS_REMOUNT //flags have been changed

 

Superblock Operations

Super block provides functions needed to access the file system and its processing. Some of the operation includes

read_inode();// must execute and Responsible for filling the submitted inode structure

write_inode(); //must execute and Used to store information about the inode structure

put_inode();// optional and Release all the blocks occupied by the inodes and release other resources

delete_inode(); //optional and Delete the inode and no longer be referenced to the filesystem

 

Inode Operation

  • Inode is useful for file management
  • Each inode contains a unique number which addressable to a file
  • Inode operations

create();//fills the mode attributes of the inode dentry

lookup();

link(); //used to create a hard link

unlink(); //deletes the file indicated by dentry.

mkdir();

rmdir();//deletes the subdirectory entry

rename(); moves a file or changes its name

permission();// checking for access rights

File and its Operation

File structure is helpful is providing

Access rights like reading and writing

Current position

Access flags and number of accesses

File Operations

read(); //read the data and put in the user address space

write();//copy data from user address space to the file

mmap(); // the file is mapped to user address space

open(); //create a file structure

flush(file); //called when the file is closed

lock(); // lock is called if file locks are set

Comments

Popular posts from this blog

Installing TexLive 2019 in Ubuntu 18.04

Installation of TexLive 2019 in Linux (Ubuntu 18.04 LTS)
TeX (Tech)

Installation of TexLive 2019

Please watch the video for full installation



I used .iso file to download, the Total size is 3.3GB for Linux,

and i used the torrent file to download, it took me just 20 min to download the entire .iso file

Extract the .iso file to a folder and open a terminal

$] sudo ./install-tl
(it goes into a terminal mode, which is faster compared to the GUI Mode)

$] sudo ./install-tl -gui
after the installation, set the PATH, MANPATH and INFOPATH as suggested by LATEX

export PATH=$PATH:/usr/local/texlive/2019/bin/x86_64-linux
export MANPATH=/usr/local/texlive/2019/texmf-dist/doc/man
export INFOPATH=/usr/local/texlive/2019/texmf-dist/doc/info

put these lines in to the /home/pradeepkumar/.bashrc

$] gedit /home/pradeepkumar/.bashrc
We have installed TexLive 2019 and texstudio.

To install texstudio

$] sudo apt install texstudio
The look and feel of TexStudio looks like this image.


texlive, it install everyt…

Implementing a new system call in Kernel version 2.6.32

A system call is used by application or user programs to request service from the operating systems. Since the user programs does not have direct access to the kernel whereas the OS has the direct access. OS can access the hardware through system calls only.The following files has to be modified for implementing a system call/usr/src/linux-2.6.32.5/arch/x86/kernel/syscall_table_32.S/usr/src/linux-2.6.32.5/arch/x86/include/asm/unistd_32.h/usr/src/linux-2.6.32.5/include/linux/syscalls.h/usr/src/linux-2.6.32.5/MakefileNew set of files to be createdCreate a new directory newcall/ inside the path “/usr/src/linux-2.6.32.5/” Create new files Makefile, newcall.c and put them in the /usr/src/linux-2.6.32.5/newcall/ folder Create new user files (in any folder of Linux) to test the system call
testnewcall.c, testnewcall.h (created in /home/pradeepkumar) syscall_table_32.S Find the file /usr/src/linux-2.6.32.5/arch/x86/kernel/syscall_table_32.S and add the following line at the end
"…

Electrical Machine Design (equations)

FactorsDC Machine Transformers Induction Machines Synchronous MachinesOutput EquationPa=CoD2Ln, where Pa=P/h for generators, Pa=P for motorsFor Single Phase
Q=2.22 f Bm Ai Kw Aw d10-3
For Three Phase
Q=3.33 f Bm Ai Kw Aw d 10-3Q=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * hQ=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * h
For Turbo alternators
Q=1.11Bavac KwsVa2 L 10-3/nsOutput CoefficientCo=Bav ac* 10-3where Bav-magnetic loading and ac - electric loadingDNACo=11 Kws Bav ac 10-3Co=11 Kws Bav ac 10-3 Choice of Magnetic LoadingFlux Density in Teeth Frequency of Flux Reversals Size of machineDNAMagnetizing current, Flux Density, Iron lossIron loss, Stability, Voltage Rating, Parallel Operation, Transient ShortCircuit current Choice of Electric LoadingTemperature rise,
speed of machine, Voltage, Armature reaction, CommutationDNAOverload Capacity, Copper losses, Temperature rise, Leakage ReactanceCopper loss, Synchronous reactance, Temperature rise, Stray Load losses,
Voltage rating Flux …