В случае ошибочной транзакции apt-get не возвращает код ошибки:
# apt-get dist-upgrade
Reading Package Lists... Done
Building Dependency Tree... Done
Calculating Upgrade... Done
The following packages will be upgraded
  dev
1 upgraded, 0 newly installed, 0 removed and 0 not upgraded.
Need to get 0B/1134kB of archives.
After unpacking 0B of additional disk space will be used.
Do you want to continue? [Y/n] 
Committing changes...
Preparing...                          
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[100%]
** Cannot install dev package: mounted udev detected.
** This is no problem, but to avoid side-effects with
** stopping and starting it automatically, please do:
service udevd umount
apt-get install dev
service udevd start
** Note that some services like syslogd might need
** restart after this, too.
error: execution of %pre scriptlet from dev-3.3.1-alt18 failed, exit status 1
error:   install: %pre scriptlet failed (2), skipping dev-3.3.1-alt18
W: Some errors occurred while running transaction
# echo $?
0