Probably a stupid question, but I simply failed to find a solution.

This is the situation:

I installed SuSE 10.3 and choose ext3 with journal=data as the file system. Since I couldn't give the size of the journal during the installation I wanted to check later and set the maximum (it's journal=data after all). So I did a which gave a lot of output / information but no journal size. So I decided to resort to brute force and issued a and got "device has already a journal".

Fine. How large? It didn't tell. When I changed the size parameter to "size=200" it didn't acknowledge the change either, it just repeated "device has already a journal".

So, how do I find out the size of an ext3 journal and how can I change its size?

I don't think you can change the size of the journal.

As a workaround you may remove journal and re-create it.

I thought of that, too. But that would mean to use a rescue CD since / and the system directories are journaled as well. And I don't know the commands .

And it doesn't answer my original question: "how do I find out the size of an ext3 journal...?" It might well be that the journals already have the maximum size (400M)...

Really nobody else?

This will remove the journal.

This will show current options.

This will create journal with desired size.

If man pages are not installed in your computer they are accessible here.

The journal is located at inode:
'tune2fs -l /dev/device | awk '/Journal.inode/ {print $3}''
The size is:
debugfs -R "stat <inodenumber>" /dev/device 2>&1| awk '/Size: / {print $6}'|head -1

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Thank you . I even read the man page -- but I need new spectacles .

P.S.: Out of curiosity: What happens when one does that to a mounted partition?

P.P.S.: Special thanks for your contribution unSpawn. Now, woudn't that be a nice improvement for tune2fs, a new option like with the output of the journal size in bytes | kB | MB | GB ...

And one could even dream of a resize option .

Since the journal file is just that, a journal, removing it from a running ext3 fs will not cause any problems. It just changes the fs from ext3 to ext2, and ext2 works fine unless an operation is aborted by, e.g., a power loss.

In fact, I believe that the partition must be mounted to remove/reinstall the journal file. How would you be able to write to the fs to make the change if the partition containing the fs was not mounted?

That's the power of GNU/Linux: you can experiment with it and find out w/o needing anyones agreement. I suggest you try it only on something disposable like a mounted loop device. And make some background process do constant read/writes while you're at it.

That's for future research.

I tested your commands on an unused partition which I had set up with a 400 MB journal using tune2fs. The journal size is returned with 419430400. That is close enough to 400MB for me but what in units is this ?

It is (10^20) *400, but is 10^20 bytes 1 MB? I always thought that is 1000*1024 bytes? Where am I wrong?

Tsk, tsk. It is (2^20) *400, but is 2^20 bytes 1 MB? I always thought that is 1000*1024 bytes?

"Where am I wrong?" Where? Well, in math at least

But I still don't get the source for that value.

This time tsk^tsk ^

1 MB = 1024*1024 = 2^10*2^10 = 2^20 = 1.048.576 byte.

And 1.048.576*400 = 419430400.

So my journal is 400 MB. Darn.

My humble apologies, unSpawn.

Attention, other newbies (like me):

Upon wanting to play with the information you'd better

• omit the dot between "Journal.inode" and make that "Journal inode"
• keep in mind that the "stat" statement is an debugfs option and not the stat command of the sh-utils, i.e. the built-in(?) tools of the shell (to find that out the hard way I needed several hours )
• "<>" are relly necessary around the inode number, just like unSpawn posted it, see "man debugfs"

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