Re: removing modules
On Sat 03 Jul 2021 at 17:50:44 (+0100), mick crane wrote:
> On 2021-07-03 17:29, The Wanderer wrote:
> > On 2021-07-03 at 12:06, mick crane wrote:
> >
> > > hello,
> > > If I type "lsmod" there is a big list of modules with many
> > > followed by a
> > > "0"
> > > which I guess means they are not needed in the kernel ?
> >
> > That depends what you mean by "needed".
> >
> > As I understand matters, what that number being nonzero means is that
> > there's something else the kernel knows about (usually another module)
> > which won't work if this module isn't loaded. In order to unload this
> > module, you'll want to unload the other one first.
> >
> > If the module is zero, that means that the kernel doesn't know of
> > anything other than that module which won't work unless the module is
> > present.
> >
> > That doesn't mean that the module itself isn't needed, however. There
> > might be some functionality which you need which is provided
> > directly by
> > that module, rather than by something which the kernel knows about and
> > considers to be "something else", but which won't work if the module
> > isn't loaded.
> >
> > For example, if the driver for your network card is contained in a
> > module, then even if no other modules depend on that one, unloading the
> > module would mean your network card would stop functioning. If you need
> > your network to be functioning, that would mean that you still need the
> > module, even though there aren't any other modules (etc.) which depends
> > on it.
> >
> > > Does lsmod know about all installed software and if a module is
> > > needed or does software have to be run first ?
> >
> > As Reco suggested, you'll have to clarify this. Most of the time,
> > software does not require loading modules; it's most often
> > hardware that
> > requires that.
> >
> > > If I don't need them can somebody remind me how I can remove modules
> > > ?
> >
> > The command to run is 'modprobe -r MODULE_NAME'.
> >
> > You can also do it with 'rmmod MODULE_NAME', but that's not usually the
> > best way; IIRC, modprobe includes smarts which rmmod doesn't.
> >
> > Both of those commands need to be run as root in order to work.
>
> I did think that modules are for the kernel to interact with hardware.
> There is for example "dell_smm_hwmon" followed "0" which you'd think
> was to be used by software for monitoring the PC hardware.
> I never used anything like that and wondered if there was some
> software that was installed that needed that module
> but I never used so it is "0" but if I used it it would change to "1".
> I looked because "apt upgrade" failed to install things in /boot
> because no room left. I deleted the oldest kernel stuff of the 3 there
> and "apt upgrade" worked.
> I was thinking then to remove the unwanted modules to make the kernels
> smaller.
> There is for example a few filesystem modules like msdos which would
> be needed if I wanted to mount an msdos filesystem.
> Seem to remember "insmod" a module if and when needed.
>
> If remove modules from kernel are the gone or are they still on disk
> and could be put back ?
OK, you're short of space in /boot. Here's mine.
$ ls -GlG /boot/
total 109828
-rw-r--r-- 1 root 3421023 Mar 19 09:29 System.map-4.19.0-16-amd64
-rw-r--r-- 1 root 3421235 Jun 21 03:46 System.map-4.19.0-17-amd64
-rw-r--r-- 1 root 206242 Mar 19 09:29 config-4.19.0-16-amd64
-rw-r--r-- 1 root 206214 Jun 21 03:46 config-4.19.0-17-amd64
drwx------ 3 root 4096 Dec 31 1969 efi
drwxr-xr-x 5 root 4096 Jun 23 13:47 grub
-rw-r--r-- 1 root 31149360 Mar 27 13:03 initrd.img-4.19.0-16-amd64
-rw-r--r-- 1 root 32309222 Jun 26 18:28 initrd.img-4.19.0-17-amd64
-rw-r--r-- 1 root 31156713 Jun 23 13:47 initrd.img-4.19.0-17-amd64.bak
-rw-r--r-- 1 root 5287168 Mar 19 09:29 vmlinuz-4.19.0-16-amd64
-rw-r--r-- 1 root 5283072 Jun 21 03:46 vmlinuz-4.19.0-17-amd64
$
So it's obvious that you need to concentrate your attention on the
initrd files. You could remove any .bak file, and even not generate
any by setting
backup_initramfs=no
in /etc/initramfs-tools/update-initramfs.conf, but you could also
save space by not storing all the modules in your initrd files.
Do this by setting
MODULES=dep
in /etc/initramfs-tools/initramfs.conf
and rebuilding it with update-initramfs.
MODULES=dep will mean that if you change your booting method,
there's a chance it could fail. In which case, you'd first boot
with the old method and rebuild an initrd with MODULES=most.
When you make these changes, just check for any parameters set in
files in /etc/initramfs-tools/conf.d because they take priority.
Cheers,
David.
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