Re: [PATCH] expand-on-first-boot: Fix early exit in helper script

[Uladzimir Bely <ubely@ilbers.de>]

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In the email from Friday, 10 June 2022 08:14:19 +03 user Jan Kiszka wrote:
> On 10.06.22 05:19, Uladzimir Bely wrote:
> > Changes in 342a751e introduced a regression when error from 'find'
> > makes helper script early exit (with -1 error code) just after an
> > attempt to assign ROOT_DEV_SLAVE variable. So, the last partition
> > remained not resized.
> > 
> > Passing 'find' output to 'head -1' masks possible error from 'find'
> > without breaking the logic and continues the script execution.
> > 
> > Signed-off-by: Uladzimir Bely <ubely@ilbers.de>
> > ---
> > 
> >  .../expand-on-first-boot/files/expand-last-partition.sh         | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git
> > a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > h
> > b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > h index f3e29a1c..934a014f 100755
> > ---
> > a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > h +++
> > b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > h @@ -11,7 +11,7 @@ set -e
> > 
> >  ROOT_DEV="$(findmnt / -o source -n)"
> >  ROOT_DEV_NAME=${ROOT_DEV##*/}
> > 
> > -ROOT_DEV_SLAVE=$(find /sys/block/"${ROOT_DEV_NAME}"/slaves -mindepth 1
> > -print -quit 2>/dev/null) +ROOT_DEV_SLAVE=$(find
> > /sys/block/"${ROOT_DEV_NAME}"/slaves -mindepth 1 -print -quit 2>/dev/null
> > | head -1)> 
> >  if [ -n "${ROOT_DEV_SLAVE}" ]; then
> >  
> >  	ROOT_DEV=/dev/${ROOT_DEV_SLAVE##*/}
> >  
> >  fi
> 
> "-quit" is supposed to obsolete "head -1". Feel free to prove me wrong,
> but that was the reason for dropping it.
> 
> Jan

Yes, "-quit" makes 'find' to exit after first match. But if nothing found, the return code of 'find' is 
"-1" and due to script's "set -e" it just exits.

An example that demonstrates the behaviour (on raspberry):

root@isar:~# cat /boot/test.sh  
#!/bin/sh 

set -e 

echo "1: start" 
ROOT_DEV="$(findmnt / -o source -n)" 
echo "2: ROOT_DEV=${ROOT_DEV}" 
ROOT_DEV_NAME=${ROOT_DEV##*/} 
echo "3: ROOT_DEV_NAME=${ROOT_DEV_NAME}" 
ROOT_DEV_SLAVE=$(find /sys/block/"${ROOT_DEV_NAME}"/slaves -mindepth 1 -print -quit 
2>/dev/null) 
echo "4: ROOT_DEV_SLAVE=${ROOT_DEV_SLAVE}" 
root@isar:~# sh /boot/test.sh  
1: start 
2: ROOT_DEV=/dev/mmcblk0p2 
3: ROOT_DEV_NAME=mmcblk0p2 
root@isar:~# echo $? 
1 
root@isar:~# ls /sys/block/ | grep mmc 
mmcblk0 
root@isar:~# 
So, the easiest way to mask error returned by 'find' is to use something like 'head -1' or 'tee /
dev/null'. In this case script just continues with empty ROOT_DEV_SLAVE.

-- 
Uladzimir Bely


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