Linux Interviews

= Basics =


 * OOM Killer

A page fault (sometimes called #PF, PF or hard fault) is a type of exception raised by computer hardware when a running program accesses a memory page that is not currently mapped by the memory management unit (MMU) into the virtual address space of a process.
 * Page Fault


 * Swap Memory

inode is the unique name given by the operating system to each file (ls -i) process id is the unique id given to each process.
 * What are Inode and Process ID?

Ready: The process is created and is ready to run Running: The process is being executed Blocked or wait: Process is waiting for input from the user Terminated or Completed: Process completed execution, or was terminated by the Operating System Zombie: Process terminated, but the information still exists in the process table.
 * What are the process states in Linux?

System Calls to manage the process: fork : Used to create a new process exec : Execute a new program wait : Wait until the process finishes execution exit : Exit from the process
 * Explain Process Management System Calls in Linux

System Calls used to get Process ID: getpid : get the unique process id of the process getppid : get the parent process unique id


 * Schedule:


 * Cron

To run a command at 4 pm every Sunday: 0 16 * * 0

echo "shutdown now" | at -m 18:00
 * at

echo $SHELL
 * Find out Shell being used:

export JAVA_HOME = /home/user/Java/bin
 * Export Command used to set and reload the environment variables:

Google
You basically answered what happens when you turn your computer on with: "The picture appears on the monitor". A proper answer involves: shell word splitting, searching PATH, loading dynamic libs, argument parsing, syscalls, /proc.
 * What happens when I type "ps" into a UNIX prompt?

Prepare to know extensively what happens at the bash layer, including the full process of shell interpretation (variables, parameter expansion). You should know how a TCP/IP connection is set up and how a webserver responds.
 * Describe exactly what happens when you type 'telnet google.com 80' at a bash prompt, including shell interpretation, network connections.

fgetpos, fseek, fsetpos, ftell, rewind - reposition a stream
 * What does fseek command in Linux/Unix do>

int fseek(FILE *stream, long offset, int whence); long ftell(FILE *stream); void rewind(FILE *stream); int fgetpos(FILE *stream, fpos_t *pos); int fsetpos(FILE *stream, const fpos_t *pos);
 * 1) include 

The fseek function sets the file position indicator for the stream pointed to by stream. The new position, measured in bytes, is obtained by adding offset bytes to the position specified by whence. If whence is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the start of the file, the current position indicator, or end-of-file, respectively. A successful call to the fseek function clears the end-of-file indicator for the stream and undoes any effects of the ungetc(3) function on the same stream.

The ftell function obtains the current value of the file position indicator for the stream pointed to by stream. The rewind function sets the file position indicator for the stream pointed to by stream to the beginning of the file. It is equivalent to: (void) fseek(stream, 0L, SEEK_SET) except that the error indicator for the stream is also cleared (see clearerr(3)).

The fgetpos and fsetpos functions are alternate interfaces equivalent to ftell and fseek (with whence set to SEEK_SET), setting and storing the current value of the file offset into or from the object referenced by pos. On some non-UNIX systems, an fpos_t object may be a complex object and these routines may be the only way to portably reposition a text stream.

Sudo cmd
aman@aman-server:~/scripts$ sudo su - root@aman-server:~# aman@aman-server:~/scripts$ sudo su root@aman-server:/home/aman/scripts#