A PCB is a process control block , this is its definition on Wikipedia
Process Control Block (PCB, also called Task Controlling Block,[1] Task Struct, or Switchframe) is a data structure in the operating system kernel containing the information needed to manage a particular process. The PCB is "the manifestation of a process in an operating system
and its duty is :
Process identification data
Processor state data
Process control data
So where is the PCB of a process to be found?
In the Linux kernel, each process is represented by a task_struct in a doubly-linked list, the head of which is init_task (pid 0, not pid 1). This is commonly known as the process table.
In user mode, the process table is visible to normal users under /proc. Taking the headings for your question:
Process identification data is the process ID (which is in the path /proc/<process-id>/...), the command line (cmd), and possibly other attributes depending on your definition of 'identification'.
Process state data includes scheduling data (sched, stat and schedstat), what the process is currently waiting on (wchan), its environment (environ) etc.
Process control data could be said to be its credentials (uid_map) and resource limits (limits).
So it all depends how you define your terms... but in general, all data about a process can be found in /proc.
init_task (pid 0, not pid 1)" There's no such thing as init_task. It's init, and its pid is 1, not 0 (confirmed via pidof init).
– AleksandrH
Sep 15 '18 at 14:42
