Category Archives: Linux

ZFS in practice – verifying transparent compression –

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I had read about the transparent compression that zfs offers. I wanted to verify it so I did, and sent my results off.

As we all know no experiment is valid unless verifiable. I wanted be sure that the transparent compression was actually working so I set up a sample zfs volume and purposefully made some files that i knew would compress really well. I grabbed their sizes, transferred them to another machine without zfs, and compared the size. It works.
filesystems usually suck

1. Create the zfs filesystem
[email protected]:~# zfs create rpool/ztest
[email protected]:~# zfs set mountpoint=/ztest rpool/ztest

as soon as you do this /ztest shows up in the filesystem
[email protected]:~# ls /ztest/

2. enable compression and set it use gzip at level 6 (default)
[email protected]:/ztest# zfs set compression=gzip rpool/ztest

3. create some files you know will compress well
time for i in $(seq 1 3); do echo -n “file${i} “; echo $(seq 1 10000000) >> file${i} 2>&1; done

4. check the compression ratio
[email protected]:/ztest# zfs get compressratio rpool/ztest
NAME         PROPERTY       VALUE        SOURCE
rpool/ztest  compressratio  3.69x        –

5. verify the compression is working by transferring the file to a machine without such an awesome FS, and checking the filesize there
[email protected]:/ztest# du -sh file1
23M     file1
scp -rvp /ztest/file1 [email protected]:/root/file1

[email protected]]# du -sh file1
83M    file1

Conclusion: transparent compression is working, and working rather well on a file I made to be easily compressed.

Stateless Linux How To:

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Stateless Linux sounds like a great idea for those of us that have many systems with similar configurations to manage. If you have never heard of the idea RTFM. I have stateless linux almost working here at my house. Here are the steps that I followed thus far.

on server system:
yum -y install cobbler
configure cobbler to manage dhcpd and start it
download Fedora 9 DVD ISO
sha1sum the iso to make sure the checksums match
mount the iso somewhere with the -o loop option eg. mount -o loop Fedora9.iso /media
import the distro into cobbler eg. cobbler import –mirror=/media/ –name=Fedora9
cp /sbin/lspci to /usr/sbin/lspci (if you skip this anaconda fails later under fedora 9)
mkdir -p /export/NFSroots/F9/
install os image into that directory eg. anaconda –headless -r /export/NFSroots/F9/ -m http://black/cobbler/ks_mirror/Fedora9/ –kickstart /var/lib/cobbler/kickstarts/f9base.ks
chroot into newly created environment
update environment (yum -y update)
create initrd
edit /etc/sysconfig/readonly-root
exit chroot
create cobbler distro
create cobbler profile
create cobbler system

on client system:
boot from lan.

Put some debian in your mouth: 24 hours of Ubuntu vs Fedora

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I had forgotten how nice apt was in relation to yum. I mean yum is great, I could never build a package manager like rpm; let alone a utility as versatile and helpful as what yum is. I may have the capacity to build something that sucks right around the level of up2date 0.6.  I had managed to keep that machine running fedora for years, beginning with fedora core 2. I had never reinstalled, or performed fresh installs during that time, I just kept modifying the repos, running yum update, and fixing major issues as they came up. That machine has gone through a lot with me; but it has always been a dev machine. From my first install of Asterisk that I would later use to build Viatalk, to being my test machine while studying for the RHCE. I appreciate what the community has given me. Without open source software I wouldn’t be a system admin. I would never have found the interest. Maybe I would be a cop.
Ubuntu as a distro feels very by the people/ for the people. Things that I didn’t expect to work like playing mp3’s out of the box did with very little work on my end. I tried it for a day, and just went right back home. To fedora 9.