In man page of ps under Process State Codes, the I flag (capital i) is not mentioned but ps aux shows the I flag in some processes as shown by the image below.

enter image description here

What does the I flag mean?

  • 5
    Please, DO NOT post pictures of text. Copying it out of terminal would have been much easier for both of us.
    – Maya
    Commented Dec 23, 2017 at 10:53

1 Answer 1


It means “idle”. This state was introduced in version 4.14 of the Linux kernel, in September 2017. It is used for kernel threads which use the TASK_IDLE state when idling, instead of TASK_INTERRUPTIBLE; in previous versions of the kernel, such threads were reported as TASK_UNINTERRUPTIBLE which was confusing.

ps reports this without needing any change itself, because it reports the state directly from /proc.

  • What is the difference between those two states? Commented Dec 22, 2017 at 19:08
  • 2
    See this commit: uninterruptible tasks contribute to the load average, so idle kernel threads idled in interruptible state, but that caused some issues, so a new “no load” state was introduced, along with a helper “idle” state. The idle state was made reportable in the later patch linked in the answer. So basically “idle” is “uninterruptible” but doesn’t contribute to the load average. Commented Dec 22, 2017 at 20:12
  • 1
    Also see htop source code - github.com/hishamhm/htop/blob/… [STATE] = { .name = "STATE", .title = "S ", .description = "Process state (S sleeping, R running, D disk, Z zombie, T traced, W paging, I idle)", .flags = 0, }
    – steve
    Commented Apr 23, 2021 at 16:50

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