busybox: add /dev/std{in, out, err} symlinks to inittab

Some applications, e.g. bashs process subsitution feature, rely on the
convention of `/dev/fd` being a symbolic link to `/proc/self/fd`.

This symbolic link and his companions `/dev/std*` are created by (e)udev [1],
but not by mdev, resulting in the following error when using the following
expression:

```
bash: /dev/fd/62: No such file or directory
```

For the sake of simplicity, lets fix this by creating the symlinks in inittab.
It is only really needed if eudev isn't used, but it doesn't really hurt to
create them even if eudev will recreate them afterwards.

Note, that we do not create the symlink `/dev/core` as `/proc/kcore` is
not available on all platforms, e.g. ARM, and the feature is not much
appreciated [2].

[1] https://github.com/gentoo/eudev/blob/8943501993322c59a6eb5be456b0d716aafff21e/src/shared/dev-setup.c#L35-L40
[2] https://lwn.net/Articles/45315/

[Peter: redirect output (errors) to /dev/null for ro rootfs]
Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

diff --git a/package/busybox/inittab b/package/busybox/inittab
index 3f49f6bd7a74abf636cceeb430bd35ed7790f642..ef58c32f0ddc3eb80adf2e5dc2b53fa5d93e38fa 100644 (file)
--- a/package/busybox/inittab
+++ b/package/busybox/inittab
@@ -19,6 +19,10 @@
 ::sysinit:/bin/mkdir -p /dev/pts
 ::sysinit:/bin/mkdir -p /dev/shm
 ::sysinit:/bin/mount -a
+null::sysinit:/bin/ln -sf /proc/self/fd /dev/fd
+null::sysinit:/bin/ln -sf /proc/self/fd/0 /dev/stdin
+null::sysinit:/bin/ln -sf /proc/self/fd/1 /dev/stdout
+null::sysinit:/bin/ln -sf /proc/self/fd/2 /dev/stderr
 ::sysinit:/bin/hostname -F /etc/hostname
 # now run any rc scripts
 ::sysinit:/etc/init.d/rcS