Category: Linux

Playing with CephFS recursive statistics

One of the cool features of CephFS is the recursive accounting the filesystem can do.

On a regular filesystem you have to use ‘du -sh’ to figure out how big a directory is. It will traverse into the directory and sum everything up for you. This can take a very long time and be very I/O intensive.

With CephFS this is done within a second:

root@admin:~# ls -alh /mnt/cephfs/
total 4.0K
drwxr-xr-x 1 root root  81T Jan 23 13:09 .
drwxr-xr-x 6 root root 4.0K Jan 13 15:41 ..
drwxrwxr-x 1 root root    0 Jan 23 12:57 DIR1
drwxrwxr-x 1 root root  80T Apr  3 11:16 DIR2
root@admin:~#

Or fetch these statistics using the virtual xattrs of CephFS:

root@admin:~# getfattr -d -m ceph.dir.* /mnt/cephfs
getfattr: Removing leading '/' from absolute path names
# file: mnt/cephfs
ceph.dir.entries="2"
ceph.dir.files="0"
ceph.dir.rbytes="88833202521902"
ceph.dir.rctime="1430297412.09159402000"
ceph.dir.rentries="10334874"
ceph.dir.rfiles="9853051"
ceph.dir.rsubdirs="481823"
ceph.dir.subdirs="2"

root@admin:~#

It is as simple as that. Using this virtual xattrs of CephFS you instantly know how much data, files and (recursive) entries there are in any directory.

No long waits on find or du, simply ask the Metadata Server of CephFS!

Limit battery state of charge on a Lenovo X1 Carbon under Ubuntu

Since the end of 2012 I have a Lenovo X1 Carbon laptop running with Ubuntu 12.04

By default a laptop charges all the way up to 100% State of Charge, something which is very bad for a battery. There is a great video on Youtube about this if you want to know all the ins and outs.

The bottom line is that I wanted to limit the charge level to 90% for my laptop. Up until now I did this manually by pulling the plug at certain points, but that didn’t always work. I sometimes forgot and the battery would charge up to 100%.

On Github I found the tpacpi-bat project which allows you to limit the charge level of your battery.

How to install?

  • Clone the project
  • Run install.pl
  • Modify your /etc/rc.local file
  • Reboot

This is what you need to put in your rc.local:

tpacpi-bat -g SP 0
tpacpi-bat -g SP 1
tpacpi-bat -g SP 2

exit 0

As far as I know the X1 Carbon has 3 batteries, so for all three we set the charge limit to 90%. This is not persistent after reboots, so we have to set it every time we boot.

You’ll now see that your battery charges to 90% at max.

Quassel IRC, never miss anything on IRC!

I was one of those guys who had irssi running inside a screen on a remote Linux box somewhere. It works just fine, but I always forgot to open the SSH session so I missed a lot of IRC conversations. Private messages were a problem as well, most of the times it was a couple of days later before I noticed somebody had actually sent me a PM…

It was time to change my IRC client, with the preference to always be online.

A short search lead me to the website of Quassel IRC, a distributed IRC server/client. Exactly what I was looking for! You just install the “core” on a remote Linux box and use the Linux, Windows, Mac OSX or Android client to participate on IRC.

The core has been running on a Ubuntu 10.04 machine for about one week now and it works like a charm. My IRC conversations are secured by SSL and I never miss a PM or when somebody tags me!

Integration of the client goes well on Ubuntu 12.04 with Unity, it integrates seamlessly with Unity and notifies me whenever I’m tagged or I receive a PM.

Looking for me on IRC? Find me on OFTC @ wido where I hang out in #ceph. Or find me on Freenode @ widodh in #cloudstack