File system – Phocean.net

Corrupted virtual disk with VMware

phocean — Sun, 16 Jan 2011 17:02:50 +0000

Wow, this article and especially one of its comments saved my day.

My computer crashed and one of the VMware machine hosted on it could not start anymore :

“Cannot open the disk ‘path of vmdk’ or one of the snapshot disks it depends on.
Reason: the specific virtual disk needs repair.

Checking on the VMware forums, I quickly found the command that was supposed to help :

$ vmware-vdiskmanager -R /path/to/disk.vmdk
The virtual disk, '/path/to/disk.vmdk', is corrupted but the repair process has failed.

Damned ! I almost resigned restoring the last backup and loosing a week of work when, by chance, I found the article mentioned above.

As recommended, I downloaded the Virtual Disk Development Kit 1.2 from VMware, untared it and still doubtfully launched :

$ ./bin64/vmware-vdiskmanager -R /path/to/disk.vmdk
The virtual disk, '/path/to/disk.vmdk', was corrupted and has been  successfully repaired.

Saved! Thanks so much to the guys. I would have never thought about trying it, I wonder how they could find it.

But how is it possible that the utility coming with vmware workstation 7.1 suck so much and is not on par with other versions ?

Btrfs : a key feature coming to Linux

phocean — Thu, 23 Apr 2009 14:17:25 +0000

Great and clear article there from Linux magazine that sums up the new BTRFS file system.

I can’t wait for it to become stable !

UPDATE 2009-02-05 : I hope to see this soon on a Linux distribution.

ACL on Linux

phocean — Sun, 25 Mar 2007 15:46:00 +0000

Rights management on Linux is enough for most use.
In a few words, a file or a directory belongs to the owner and what you can do is positionning some right to this owner, to his group or all other users (= guests).
This is not bad, but sometimes you (or your application) may need more advanced right management, as on the latest windows versions : putting several owners with different rights, inheritance, etc.
There are named ACL (Access List Management) and they are supported on Linux also.
This is not going to be an how-to but just a brief informative introduction to ACL on Linux. You will find many how-to on the web if you need more.

Fisrt, you will need a kernel that supports ACL. As far as I now, most of modern distributions include it in their 2.6.x kernel.

To ensure, type :

$ grep ACL /boot/config-kernel-version

If your kernel supports it, you will get many lines like :

CONFIG_FS_POSIX_ACL=y
CONFIG_EXT3_FS_POSIX_ACL=y
...

If you don’t, you will have to recompile your kernel with the right module.

Let’s say that we are going to add ACL management to the /home partition (on /dev/sda3) :

$ mount -t ext3 -o defaults,acl /dev/sda3/ /home

Or, if /home were already mounted :

$ mount -o remount,acl /home

If you want to add it at startup, edit /etc/fstab in the following way :

/dev/sda3       /home               ext3    defaults,acl 0       0

Now take your favorite packages manager and set up ACL tools, which allow us to assign ACL to files. Mine will be :

$ apt-get install acl

Now you can assign ACL using setfacl or consulting them using getfacl.
Use man to get some precise examples of syntax.

Be advised of the following :
– using cp with default does not preserve ACL. Use cp -a.
– using mv always keep ACL.
– in any case, if you copy/move files to a partition which is not mounted with ACL management (or with a file system that does not support it), ACL are lost.
– ls -l gives an output with a ‘+‘, that indicates that some ACL are presents. For more information, use getfacl.
– KDE supports ACL in its interface, but Gnome does not yet. Maybe there is a workaround, but I haven’t tried yet.