[SOLVED] running a string as a command as it pertains to mkinitrd_command_generator.sh

Daedra · 01-30-2022, 09:54 AM

I have a script I wrote that updates my kernels for all my machines whether they be bare metal, virtual, 32bit or 64bit. I am making some tweaks to it. I can run the the output mkinitrd_command_generator.sh as a command two different ways

using eval

Code:

eval $(sh /usr/share/mkinitrd/mkinitrd_command_generator.sh -r)

or pipe it to bash

Code:

sh /usr/share/mkinitrd/mkinitrd_command_generator.sh -r | bash

My questions is, does it matter which way I do it or are both acceptable ways in your guys opinion?

Thanks.

luvr · 01-30-2022, 11:21 AM

Quote:

Originally Posted by Daedra

using eval

Code:

eval $(sh /usr/share/mkinitrd/mkinitrd_command_generator.sh -r)

If I remember correctly, you don't even need the "eval".
Cannot check at the moment, but just

Code:

$(/usr/share/mkinitrd/mkinitrd_command_generator.sh -r)

should suffice, I believe.

Daedra · 01-30-2022, 12:38 PM

Yes you are correct, that also works. I am mostly just wondering if there is a generally accepted "best practice" or if it doesn't matter.

kaott · 01-30-2022, 12:51 PM

I think the only real difference in this case is avoiding a subshell or not (and the quirks that come with subshells, e.g. setting a variable in a subshell isn't reflected in parent shell). Eval has the usual security concerns of passing unsanitized inputs to it, but in this case either should be fine.

luvr · 01-30-2022, 01:23 PM

Quote:

Originally Posted by Daedra

I am mostly just wondering if there is a generally accepted "best practice" or if it doesn't matter.

No idea if there's a "generally accepted" answer, but my personal preference goes to the simplest solution. When I develop a script, I sometimes arrive at a solution that, while it does work, later on turns out to be far more complicated than it needs to be. To me, then, the simpler solution usually looks like the more elegant one, as well, and I tend to prefer it.

fourtysixandtwo · 01-30-2022, 02:41 PM

Not the answer you are asking for, but another solution is to just use the -c option and pipe it to /etc/mkinitrd.conf on the initial install once. Then you just need to run "mkinitrd -F -k $kernel_version" from then on.

Any particular reason you need to generate it fresh every time?

Daedra · 01-30-2022, 03:03 PM

Quote:

Originally Posted by fourtysixandtwo

Not the answer you are asking for, but another solution is to just use the -c option and pipe it to /etc/mkinitrd.conf on the initial install once. Then you just need to run "mkinitrd -F -k $kernel_version" from then on.

Any particular reason you need to generate it fresh every time?

I use mkinitrd.conf on all my main machines, the mkinitrd_command_generator.sh is for throw away vm's.

fourtysixandtwo · 01-30-2022, 03:19 PM

Quote:

Originally Posted by Daedra

I use mkinitrd.conf on all my main machines, the mkinitrd_command_generator.sh is for throw away vm's.

Cool, I'll just shut up then!

Daedra · 01-30-2022, 03:47 PM

Quote:

Originally Posted by fourtysixandtwo

Cool, I'll just shut up then!

Not at all, TBH honest I had forgot about it and I could change the script to do that. My script already checks for a minitrd.conf first and if it doesn't find it then it uses mkinitrd_command_generator.sh. It does make sense to create one but with throw away VM's mkinitrd_command_generator.sh is good enough.