[PATCH] fsck.xfs: fix fsck.xfs run by different shells when fsck.mode=force is set

[Gerald Yang <gerald.yang@canonical.com>]

When fsck.mode=force is specified in the kernel command line, fsck.xfs
is executed during the boot process. However, when the default shell is
not bash, $PS1 should be a different value, consider the following script:
cat ps1.sh
echo "$PS1"

run ps1.sh with different shells:
ash ./ps1.sh
$
bash ./ps1.sh

dash ./ps1.sh
$
ksh ./ps1.sh

zsh ./ps1.sh

On systems like Ubuntu, where dash is the default shell during the boot
process to improve startup speed. This results in FORCE being incorrectly
set to false and then xfs_repair is not invoked:
if [ -n "$PS1" -o -t 0 ]; then
        FORCE=false
fi

Other distros may encounter this issue too if the default shell is set
to anoother shell.

Check "-t 0" is enough to determine if we are in interactive mode, and
xfs_repair is invoked as expected regardless of the shell used.

Fixes: 04a2d5dc ("fsck.xfs: allow forced repairs using xfs_repair")
Signed-off-by: Gerald Yang <gerald.yang@canonical.com>
---
 fsck/xfs_fsck.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fsck/xfs_fsck.sh b/fsck/xfs_fsck.sh
index 62a1e0b3..19ada9a7 100755
--- a/fsck/xfs_fsck.sh
+++ b/fsck/xfs_fsck.sh
@@ -55,12 +55,12 @@ fi
 # directly.
 #
 # Use multiple methods to capture most of the cases:
-# The case for *i* and -n "$PS1" are commonly suggested in bash manual
+# The case for *i* is commonly suggested in bash manual
 # and the -t 0 test checks stdin
 case $- in
 	*i*) FORCE=false ;;
 esac
-if [ -n "$PS1" -o -t 0 ]; then
+if [ -t 0 ]; then
 	FORCE=false
 fi
 
-- 
2.43.0