What states can a process be in Linux?

In Linux, a process can be in the following main states:

• R (Running) — the process is executing or ready to execute (waiting for the CPU).
• S (Sleeping) — the process is sleeping, waiting for an event or resource (usually interruptible sleep).
• D (Uninterruptible Sleep) — the process is in uninterruptible sleep, usually waiting for I/O.
• Z (Zombie) — the process has finished, but its parent has not yet read its exit status.
• T (Stopped) — the process is stopped (for example, by SIGSTOP or a debugger).

There are also less common states, such as:

• I (Idle) — the process is waiting in the kernel (on some systems).

These states can be seen, for example, using the ps command in the STAT column.