Re: [gentoo-dev] mount portage from squashfs

[Bruno]

I'm doing more or less the same here for a few years already, works
pretty well. I think others are as well.
Doing the sync only on one system (and applying patches to the tree
where needed) and then locally copying the image to systems.

Big advantage I see is more efficient access to portage tree and less
disk usage on all systems (even the master system except for the
duration of the sync)

On master system I do the following:
  dd if=/dev/zero of=/tmp/portage.img size=384m
  mkfs.ext2 /tmp/portage.img
  mkdir /tmp/portage
  mount /tmp/portage.img /tmp/portage -o loop
  cp -a /usr/portage/* /tmp/portage
  umount /usr/portage
  mount /tmp/portage /usr/portage --move
  emerge --sync
  (apply patches)
  mksquashfs /usr/portage /tmp/portage.sqsh $options
  umount /usr/portage
  rm -f /tmp/portage.img
  mv /tmp/portage.sqsh $target
  mount $target /usr/portage -o loop

This is pretty quick (and ext2 image on tmpfs uses less memory at the
end of the day than what would be needed for putting portage tree on
tmpfs)
After that I can fetch the sqsh image from any client system when I do
updates over there (I even keep a few weeks worth of images on the
master in case one would be needed)

Only thing to take care of is mounting RW filesystem
over /usr/portage/distfiles and /usr/portage/packages or adjusting
make.conf so portage can download distfiles and if asked to same
binpkgs.

If there is some interest, I can share my script which does the whole
process.

Having tree snapshots that are currently available as tarballs also
available as squashfs images would be nice, more or less same download
size but easier to access (e.g. no need to unpack)

Bruno

On Wed, 12 August 2009 Francesco R <vivo75@×××××.com> wrote:
> Proposal, create snapshots of portage as squashfs iso, to be used in
> place of /usr/portage directory.
> prior art: see #1
>
> Already working here: one central server which keep the portage full
> tree and that after a sync create "portage.sqsh" a squashfs 4.0 iso.
>
> Advantages  are mainly:
> - cleaner root directory (ext4: du -sh /usr/portage ~= 600M | find
> /g/portage | wc -l ~= 130000)
> - faster `emerge --sync`  with fast connections
> - faster `emerge -uDpvN world`
> - less cpu/disk load on the server (if not serving from memory)
>
> Disadvantages
> - need to mount portage, or to use autofs
> - need kernel >= 2.6.30
> - bigger rsync transfer size (?= 2x) #2
> - bigger initial transfer size, lzma snapshot currently weight 30.8M,
> portage.sqsh 45M
>
> How it's done here:
> Currently on the dispatcher the following run after every emerge
> --sync:
>
> mksquashfs /usr/portage /srv/portage.sqsh \
>            -noappend -no-exports -no-recovery -force-uid 250
> -force-gid 250
>
> The clients run from cron the following:
> umount /g/portage 2>/dev/null \
> ; cp /srv/server/portage.sqsh /var/tmp/portage.sqsh \
> && mount /usr/portage
>
> /etc/fstab:
> /srv/server/portage.sqsh  /usr/portage  squashfs  loop,ro,noauto 1 1
>
> some real data:
>
> stats for a portage sync, one day
>
> Number of files: 136429
> Number of files transferred: 326
> Total file size: 180345216 bytes
> Total transferred file size: 1976658 bytes
> Literal data: 1976658 bytes
> Matched data: 0 bytes
> File list size: 3377038
> File list generation time: 0.001 seconds
> File list transfer time: 0.000 seconds
> Total bytes sent: 47533
> Total bytes received: 4120255
>
> sent 47533 bytes  received 4120255 bytes  124411.58 bytes/sec
> total size is 180345216  speedup is 43.27
>
> stats for a portage.sqsh sync, one day
>
> Number of files: 1
> Number of files transferred: 1
> Total file size: 46985216 bytes
> Total transferred file size: 46985216 bytes
> Literal data: 8430976 bytes
> Matched data: 38554240 bytes
> File list size: 27
> File list generation time: 0.001 seconds
> File list transfer time: 0.000 seconds
> Total bytes sent: 48096
> Total bytes received: 8454837
>
> sent 48096 bytes  received 8454837 bytes  5668622.00 bytes/sec
> total size is 46985216  speedup is 5.53
>
>
>
> #1 http://forums.gentoo.org/viewtopic-p-2218914.html
>    http://www.mail-archive.com/gentoo-dev@g.o/msg05240.html
>
> #2 May be mitigated by mksquashfs '--sort' option, to be tested
>
> - francesco (vivo)