Question

does a zombie process use CPU time true or false

and is it true or false that a orphan process will find a new parent and will not use CPU time.

Answer 1

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does a zombie process use CPU time true or false -:

• NO, the Zombie process doesn't use CPU time.
• a zombie process or defunct process is a process that has completed execution (via the exit system call) but still has an entry in the process table: it is a process in the "Terminated state".
• This occurs for the child processes, where the entry is still needed to allow the parent process to read its child's exit status: once the exit status is read via the wait system call, the zombie's entry is removed from the process table and it is said to be "reaped".
• A child process always first becomes a zombie before being removed from the resource table. In most cases, under normal system operation zombies are immediately waited on by their parent and then reaped by the system – processes that stay zombies for a long time are generally an error and cause a resource leak, but the only resource they occupy is the process table entry – process ID.
  
• So, All the memory and resources allocated to a process are deallocated when the process terminates using the exit() system call. But the process’s entry in the process table is still available. This process is now a zombie process.
• The exit status of the zombie process can be read by the parent process using the wait() system call. After that, the zombie process is removed from the system. Then the process ID and the process table entry of the zombie process can be reused.
• If the parent process does not use the wait() system call, the zombie process is left in the process table. This creates a resource leak.
• If the parent process is not running anymore, then the presence of a zombie process indicates an operating system bug. This may not be a serious problem if there are a few zombie processes but under heavier loads, this can create issues for the system such as running out of process table entries.

Is it true or false that a orphan process will find a new parent and will not use CPU time.

• It is false that a orphan process will find a new parent and will not use CPU time, when the parent of chid process is terminated/ died then this orphaned child process is adopted by
  special init system process: the kernel sets the parent to init.
• This operation is called re-parenting and occurs automatically. Even though technically the process has the "init" process as its parent, it is still called an orphan process since the process that originally created it no longer exists. In other systems orphaned processes are immediately terminated by the kernel.
• it still use the resources and CPU time for execution .
• An orphan process is a process that is still executing, but whose parent has died. When the parent dies, the orphaned child process is adopted by init or systemd (process ID 1).
• When orphan processes die, they do not remain as zombie processes; instead, they are waited on by init. The result is that a process that is both a zombie and an orphan will be reaped automatically.

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