[systemd-devel] experiments with 'minimal build'

[Greg KH]

On Thu, Mar 19, 2015 at 08:39:18AM -0700, Alison Chaiken wrote:
> I ran systemd 219 with most recent patches and
> 
> -PAM -AUDIT -SELINUX -IMA -APPARMOR -SMACK +SYSVINIT -UTMP
> -LIBCRYPTSETUP -GCRYPT -GNUTLS -ACL -XZ -LZ4 -SECCOMP +BLKID -ELFUTILS
> +KMOD -IDN
> 
> and, to compare, with
> 
> +PAM +AUDIT +SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP
> +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ -LZ4 -SECCOMP +BLKID +ELFUTILS
> +KMOD +IDN
> 
> Checking memory RSS usage with 'sudo pmap -x -p 1' as suggested by
> Mantas, the former case uses about 5 MB, while the later consumes
> close to 9 MB.    I'm sure that with statically compiled kernel and
> appropriate fstab that KMOD and BLKID are not needed either, but I
> doubt that they affect memory usage much.
> 
> http://freedesktop.org/wiki/Software/systemd/MinimalBuilds/ says that
> the minimum requirements are udev and journald.   I wonder if udev is
> really needed if the kernel is completely statically compiled and
> module loading is disabled?   That is a common use case for many
> embedded devices.

static compilation doesn't affect the ability to plug in dynamic devices
into your system, like USB :)

That being said, you can run an embedded system without udev, just use
the kernel devtmpfs and you should be fine.  But watch out, you usually
quickly need/want to determine your hardware types and locations, and
need libudev, so I really recommend adding it.

thanks,

greg k-h