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Groups > linux.debian.bugs.rc > #389932

Bug#1103152: Starts 2nd getty on hvc0, making console login (almost) impossible

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On Wed, Apr 16, 2025 at 12:50:13AM +0200, Lorenzo wrote:

> > This system doesn't have a /dev/ttyS0, but that doesn't stop the
> > getty-ttyS0 service from doing this:
> > 
> > --- 8< ---
> 
> [snip]
> 
> > fi
> > + pgrep -x agetty -t hvc0
> > + pgrep -x fgetty -t hvc0
> > 
> [snip]

Ah, right. It didn't catch my getty, because it's neither agetty nor fgetty but plain getty:

root      1979  0.0  0.0   2344   160 ?        Ss    2023   0:21  \_ runsv getty-hvc0
root     18185  0.0  0.0   2660   944 ?        S    Apr14   0:00  |   \_ /sbin/getty 38400 hvc0

And also because getty's controlling tty isn't /dev/hvc0; it uses (has an FD open for) that character device, but it's not its ctty:

# pgrep -x getty -t hvc0
[1]    32407 exit 1     pgrep -x getty -t hvc0

> > if fuser -v "$SGETTY" 2>&1 | grep -q getty; then exec sleep 3600; fi
> 
> So, something like this already happened (#895904) and I thought we
> already have a test in the run script, 
> 
> pgrep -x agetty -t "$SGETTY"
> pgrep -x fgetty -t "$SGETTY"

Unfortunately, this test apparently just doesn't work. The getty process has no controlling tty:

# cat /proc/18185/stat
18185 (getty) S 1979 1979 1979 0 -1 4194560 159 0 0 0 0 1 0 0 20 0 1 0 6638251059 2723840 236 18446744073709551615 94739846283264 94739846346029 140721031136256 0 0 0 0 131078 0 1 0 0 17 0 0 0 0 0 0 94739846374864 94739846378704 94739860475904 140721031143277 140721031143300 140721031143300 140721031143404 0

(Field 7 is zero; it should contain the device number of the ctty.)

I suppose if I were to start getty from a terminal, it would have a ctty, but that would be the terminal it was started from, not the one it's managing.

> About the test I was wondering if a plain
> 
> pgrep -t "$SGETTY"
> 
> would be correct (disregarding the name of the process).
> If there is a process on the getty can I assume the getty is busy?

Apparently not; see above.

> About the missing dependency, I'm not eager to add one, so I was
> thinking of a recommend and make the test conditional to
> [ -e /usr/bin/pgrep ]

I don't think you should do this. `pgrep` could be anywhere on the PATH; if it doesn't exist, you won't be able to run it anyway, so testing for its existence in a particular directory doesn't improve anything, just causes pgrep not to be run if it's in an unexpected location.

That said, the pgrep test seems to be completely unreliable.

I still think the best would be not to install this service by default, because making it robust enough would make it too complex.

> > 1. if /dev/$SGETTY is not found, you stop the service; but maybe the
> > getty will appear later, for example when a module is loaded, or a

The tty, not the getty (sorry if this was confusing)

András

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Thread

Bug#1103152: Starts 2nd getty on hvc0, making console login (almost) impossible Andras Korn <korn-debbugs@elan.rulez.org> - 2025-04-14 16:40 +0200
  Processed: Re: Bug#1103152: Starts 2nd getty on hvc0, making  console login (almost) impossible "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-04-16 01:00 +0200
  Processed: Re: Bug#1103152: Starts 2nd getty on hvc0, making  console login (almost) impossible "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-04-16 01:00 +0200
  Bug#1103152: Starts 2nd getty on hvc0, making console login (almost) impossible Lorenzo <plorenzo@disroot.org> - 2025-04-16 11:10 +0200
  Processed: Re: Bug#1103152: Starts 2nd getty on hvc0, making  console login (almost) impossible "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-04-16 11:10 +0200
  Bug#1103152: Starts 2nd getty on hvc0, making console login (almost) impossible Andras Korn <korn-debbugs@elan.rulez.org> - 2025-04-16 16:40 +0200
    Bug#1103152: Starts 2nd getty on hvc0, making console login  (almost) impossible Lorenzo <plorenzo@disroot.org> - 2025-04-17 00:30 +0200
  Bug#1103152: Starts 2nd getty on hvc0, making console login (almost) impossible Andras Korn <korn-debbugs@elan.rulez.org> - 2025-04-22 10:20 +0200
  Processed: Re: Bug#1103152: Starts 2nd getty on hvc0, making  console login  (almost) impossible "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-04-26 19:30 +0200
  Bug#1103152: marked as pending in runit Lorenzo Puliti <noreply@salsa.debian.org> - 2025-04-27 00:50 +0200
  Processed: Bug#1103152 marked as pending in runit "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-04-27 00:50 +0200
  Bug#1103152: marked as done (Starts 2nd getty on hvc0, making  console login (almost) impossible) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-04-30 10:00 +0200

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