SUMMARY: Shells/Dynamically Linked

From: Joseph P Frazee <>
Date: Wed Aug 08 2001 - 12:26:07 EDT
> We are currently in the process of trying to standardize our choice of
> shells for system administration scripts and some concern (from other
> than myself) has been voiced about using a dynamically linked shell
> sysadmin tasks run as root or by system processes.
> Basically, where can I find a couple of resources to justify the usage
> of bash or ksh over sh while addressing this issue?
> I frankly don't think its a problem as long as it's not whatever init
> first calls... I'm just looking for my proof

These were the two most helpful comments:

'If you used /sbin/sh you will not be using the dynamically link shell
however if you use /usr/bin/sh then you will be using dynamically link
shell, which mean you can still use the "sh" and not necessaryly have it
dynamically link which you don't want anyway.

The reason why one should not have root login shell dynamically link is
that if for any reason you have file system "/usr" mounted on a separate
partition and it can not be mounted at boot time then you will not be
able to login onto system.'


'Aside from that, this is largely a "holy war" issue.'

On top of that,

has a good account of the whats and whys.

Of important notice is,

'From 2.3 onword (1994?) all syste rc scripts are executed under sh
regardless of the root shell (see /etc/rcS).'

The moral of the story being:

(1.) Its slightly more risky changing root's shell because if /usr is
hosed, then system support will be difficult, i.e. impossible.

(2.) Some people like to change root's shell. Other's think it's evil.

(3.) Using a dynamically linked shell for maintenance scripts not
crucial for single-user system startup will have no detrimental effect
because doing so in no way requires root's shell to be changed. And
scripts useful only in a multi-user runlevel presuppose /usr being

(4.) Even ls is dynamically linked so if a dynamically linked shell is
not good enough for system non-essential scripts, ls probably isn't


Joseph P Frazee
Received on Wed Aug 8 17:26:07 2001

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