writing /dev/console doesn't work after STDIN/STDOUT/STDERR are all closed #9212
Description
I'm trying to run sysvinit in docker, although it basically works, sysvinit's output disappears.
The command below is to reproduce the issue, seems STDIN/STDOUT/STDERR are dup-ed
file descriptors to the file descriptor of pseudo tty slave /dev/console, when STDIN/STDOUT/STDERR
are closed, no more reference to the opened pseudo tty slave /dev/console, thus /dev/console
is closed. Thus I can't find logs of /sbin/init on my terminal emulator and "docker logs".
Nothing outputs after STDIN/STDOUT/STDERR are closed:
$ docker run --rm -t debian:jessie perl -le \
'close(STDIN); close (STDOUT); close(STDERR); system("ls -l /dev /proc/1/fd >/dev/console")'
Have output when at least one of STDIN/STDOUT/STDERR isn't closed:
$ docker run --rm -t debian:jessie perl -le \
'close (STDERR); close(STDOUT); system("ls -l /dev /proc/1/fd >/dev/console")'
/dev:
total 0
crw------- 1 root root 136, 2 Nov 17 20:00 console
lrwxrwxrwx 1 root root 13 Nov 17 20:00 fd -> /proc/self/fd
crw-rw-rw- 1 root root 1, 7 Nov 17 20:00 full
c--------- 1 root root 10, 229 Nov 17 20:00 fuse
lrwxrwxrwx 1 root root 11 Nov 17 20:00 kcore -> /proc/kcore
crw-rw-rw- 1 root root 1, 3 Nov 17 20:00 null
lrwxrwxrwx 1 root root 8 Nov 17 20:00 ptmx -> pts/ptmx
drwxr-xr-x 2 root root 0 Nov 17 20:00 pts
crw-rw-rw- 1 root root 1, 8 Nov 17 20:00 random
drwxrwxrwt 2 root root 40 Nov 17 20:00 shm
lrwxrwxrwx 1 root root 15 Nov 17 20:00 stderr -> /proc/self/fd/2
lrwxrwxrwx 1 root root 15 Nov 17 20:00 stdin -> /proc/self/fd/0
lrwxrwxrwx 1 root root 15 Nov 17 20:00 stdout -> /proc/self/fd/1
crw-rw-rw- 1 root root 5, 0 Nov 17 20:00 tty
crw-rw-rw- 1 root root 1, 9 Nov 17 20:00 urandom
crw-rw-rw- 1 root root 1, 5 Nov 17 20:00 zero
/proc/1/fd:
total 0
lrwx------ 1 root root 64 Nov 17 20:00 0
lr-x------ 1 root root 64 Nov 17 20:00 1
Not quite sure what the "0 -> /2" below means, maybe procfs says it's a symlink to device (136, 2), aka the /dev/console.
$ docker run --rm -t debian:jessie ls -l /dev /proc/1/fd
/dev:
total 0
crw------- 1 root root 136, 2 Nov 17 20:01 console
lrwxrwxrwx 1 root root 13 Nov 17 20:01 fd -> /proc/self/fd
crw-rw-rw- 1 root root 1, 7 Nov 17 20:01 full
c--------- 1 root root 10, 229 Nov 17 20:01 fuse
lrwxrwxrwx 1 root root 11 Nov 17 20:01 kcore -> /proc/kcore
crw-rw-rw- 1 root root 1, 3 Nov 17 20:01 null
lrwxrwxrwx 1 root root 8 Nov 17 20:01 ptmx -> pts/ptmx
drwxr-xr-x 2 root root 0 Nov 17 20:01 pts
crw-rw-rw- 1 root root 1, 8 Nov 17 20:01 random
drwxrwxrwt 2 root root 40 Nov 17 20:01 shm
lrwxrwxrwx 1 root root 15 Nov 17 20:01 stderr -> /proc/self/fd/2
lrwxrwxrwx 1 root root 15 Nov 17 20:01 stdin -> /proc/self/fd/0
lrwxrwxrwx 1 root root 15 Nov 17 20:01 stdout -> /proc/self/fd/1
crw-rw-rw- 1 root root 5, 0 Nov 17 20:01 tty
crw-rw-rw- 1 root root 1, 9 Nov 17 20:01 urandom
crw-rw-rw- 1 root root 1, 5 Nov 17 20:01 zero
/proc/1/fd:
total 0
lrwx------ 1 root root 64 Nov 17 20:01 0 -> /2
lrwx------ 1 root root 64 Nov 17 20:01 1 -> /2
lrwx------ 1 root root 64 Nov 17 20:01 2 -> /2
lr-x------ 1 root root 64 Nov 17 20:01 3 -> /proc/1/fd