Date: Tue, 16 Oct 2012 17:40:57 -0400 From: Rick Miller <vmiller@hostileadmin.com> To: Devin Teske <dteske@freebsd.org> Cc: Stanislav Zaharov <root.vagner@gmail.com>, freebsd-questions@freebsd.org Subject: Re: MFS root filesystem and static binaries size Message-ID: <CAHzLAVF15XqN6tvxvT-mEvVXY=r0-hehfRZn=M4PgmCqz3d-QA@mail.gmail.com> In-Reply-To: <79906B82-7EF3-44DD-95A1-EF1DD239E2CD@fisglobal.com> References: <CAFDDX68DyV9ad9qfLWqAKmwVYOxYwBvdEKmFWU%2BnMpEurAvuig@mail.gmail.com> <79906B82-7EF3-44DD-95A1-EF1DD239E2CD@fisglobal.com>
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Kudos to Devin for his explanation! On Tue, Oct 16, 2012 at 4:13 PM, Devin Teske <devin.teske@fisglobal.com> wr= ote: > > On Oct 16, 2012, at 11:13 AM, Stanislav Zaharov wrote: > >> Hello, >> >> I have a question regarding the mfsroot file system organization on >> installation cd. >> How is it possible that we have bigger binary files in ls list while act= ual >> occupied space is less. > > The beauty of crunchgen(1). > > If you use the "-i" flag to ls, you'll see the inode numbers (and subsequ= ently notice that a great-many inodes are identical). > > When two files have the same inode, they are "hard links" to each other. = Unlike a "soft link" (or "symbolic link" as they are more appropriately cal= led), which stores a destination-path of the target, a hard link instead lo= oks and acts no different than the original in every way. > > So, I can hear you asking, if all these binaries are linked to the same f= ile, what file is that? > > /stand/boot_crunch > > This is a "crunched" binary (produced by crunchgen(1)). > > Here's the configuration file that is fed to crunchgen(1) that produces t= his binary: > > http://svn.freebsd.org/base/stable/9/release/i386/boot_crunch.conf > > Quite simply, crunchgen(1) takes a list of programs (progs) and libraries= (libs) and produces a "crunched" binary. > > You then create links (hard or soft) to the crunched binary. The crunched= binary knows by argv[0] which main() subroutine to invoke. > > This ultimately allows things to stay nice and tight (storage space-wise)= . > > > >> But when we try to copy these files on similar >> filesystem using cp or dd the actual used space is bigger? >> > > cp(1) doesn't track hard-links. > > tar(1) does. > > If you want to copy /stand out of the mfsroot, you can do this: > > mkdir /stand2 > tar cf - /stand | tar xf - -C /stand2 > > A corresponding "ls -li /stand2" should show that the majority of files a= ll have the same inode (whereas if you use cp, "ls -li" will instead show d= ifferent inodes for every file that was copied, because again, cp(1) does n= ot support retention of hard-links). > > > > >> For example when we mount mfsroot image we get: >> >> $ df -h /mnt/ >> >> Filesystem Size Used Avail Capacity Mounted on >> /dev/md0 3.9M 3.3M 534k 86% /mnt >> >> $ ls -lhs /mnt/stand >> ... >> 766 -r-xr-xr-x 30 root wheel 3M 10 apr 2012 dhclient >> 766 -r-xr-xr-x 30 root wheel 3M 10 apr 2012 cpio >> 766 -r-xr-xr-x 30 root wheel 3M 10 apr 2012 camcontrol >> 766 -r-xr-xr-x 30 root wheel 3M 10 apr 2012 boot_crunch >> ... >> >> But: >> >> $ du -hc /mnt/stand >> ... >> 3,2M total >> >> >> But if we copy these files onto another UFS filesystem we really consume >> the space: >> >> $ cp -a /mnt/stand /tmp/stand >> >> $ du -hc /tmp/stand >> ... >> 91M total >> >> >> How is it possible and why does it matter for mfsroot? >> > > The reason crunchgen(1) is used to create /stand/boot_crunch for the inst= all media (mfsroot) is to save space and simplify the environment. When usi= ng a crunched binary, there are no libraries to worry about for example (al= l the libraries are compiled-in). > -- > Cheers, > Devin > > _____________ > The information contained in this message is proprietary and/or confident= ial. If you are not the intended recipient, please: (i) delete the message = and all copies; (ii) do not disclose, distribute or use the message in any = manner; and (iii) notify the sender immediately. In addition, please be awa= re that any message addressed to our domain is subject to archiving and rev= iew by persons other than the intended recipient. Thank you. > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.o= rg" --=20 Take care Rick Miller
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