[Buildroot] [git commit branch/2018.02.x] busybox: add /dev/std{in, out, err} symlinks to inittab

Peter Korsgaard peter at korsgaard.com
Sun Jun 17 15:34:14 UTC 2018

commit: https://git.buildroot.net/buildroot/commit/?id=66e9e291a81c7cbf343693cda5d4642aaedf7276
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2018.02.x

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

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 at embedded.rocks>
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>

(cherry picked from commit 456ea9871ea015fe2c5a7eb79c4762787286fa56)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
 package/busybox/inittab | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/package/busybox/inittab b/package/busybox/inittab
index 368b037ee2..7cd203de0b 100644
--- a/package/busybox/inittab
+++ b/package/busybox/inittab
@@ -18,6 +18,10 @@
 ::sysinit:/bin/mount -o remount,rw /
 ::sysinit:/bin/mkdir -p /dev/pts /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

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