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Explain monolithic kernel
an operation system architecture where the entire operating system is working in kernel space and is alone in supervisor mode.
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Explain microkernel
minimum amount of software which provides only basic IPC, virtual memory and scheduling. Protocol stacks, device driver and file systems are run in user mode
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Is Linux Monolithic kernel?
No, microkernel
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Explain preemption
temporarily interrupting a task without requiring its cooperation and with the intention of resuming the task at a later time
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Is Linux preemptive kernel?
Yes as of Linux kernel 2.6 and 3.x
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Explain time slice or quantum
The period of time for which a process is allowed to run in a preemptive multitasking system
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Explain preemptive multitask
Using interruption to make running process interrupted and ask scheduler to decide which process is to run next
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Explain soft link
a special type of file that contains a reference to another file or directory. Also called as sympolic link or symlink
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Explain hard link
A directory entry that associates a name with a file on a file system. It's like an alias
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List up 5 main components of Linux Kernel
- 1. Interrupt handler
- 2. Scheduler
- 3. Memory Manager
- 4. Networking
- 5. Inter-Process Communication (IPC)
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Explain difference between soft link and hard link
Hard link is a link to another file or directory while softlink is a link to a file name. If a file is removed, hardlink will be automatically updated but softlink not
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To ensure that a file is not destroyed until all links to it are remove, what does linux do?
each inode contains a link count that keeps track of the number of links within the file system that point to it. When a pathname is unlinked, the link count is decremented by one. Only when it reaches zero are the inode and its associated data actually removed from the file system
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Hard links can not span file systems. Why?
Because an inode number is meaningless outside of the inode's own file system
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Symlink looks like regular files. Why?
Because symlink has its own inode and data chunk which contains the complete pathname of the linked-to file.
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Symlink can point a file that resides on different file system. Why?
Because the symlink has its own data chunk containing complete path name of the linked-to file
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Explain character device
- devices through which the system transmits data one character at a time by.
- For example keyboard, mouse, serial modem etc
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Explain block device
- device that moves data in the form of blocks by.
- e.g. hard disks, CD-ROMs, memory etc
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In Character devices, when there are no more chars left to read, what does the devices return?
EOF
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Explain named pipe
An IPC mechanism that provides a communication channel over a file descriptor, accessed via a special file. Also called as a FIFO special file
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Explain regular pipe
the output of one program into the input of another. Pipe is created in memory via a system call and does not exist on any filesystem
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Explain socket
One of a special file which is one of IPC mechanisms.
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What is the smallest addressable unit on a block device?
sector
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What size is common for sectors?
512 bytes
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Can block device transfer or access a unit of data smaller than a sector?
No
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What is the smallest logically addressable unit on a file system?
block
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What size is usually set for a block?
size of sector ^ 2
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Explain page size
the smallest unit addressable by the memory management unit, a hardware component
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Blocks must be smaller than the page size. Yes or no?
Yes
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What are common block sizes?
512 bytes, 1KB and 4KB
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Explain per-process namespaces
Per-process namespaces allow each process to have a different mount point sets. By default each process inherits the namespace of its parent, but a process may elect to create its own namespace with its own set of mount points and a unique root directory
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