Just installed latest updates, and since that included a new kernel I did a reboot. When it got to the filesystem checks, a brand new message I've never seen came out for each filesystem: "adding dirhash hint to filesystem".
In the words of Carol Cleveland: "What on earth does that mean?"
On Fri August 24 2007, Tom Horsley wrote:
Just installed latest updates, and since that included a new kernel I did a reboot. When it got to the filesystem checks, a brand new message I've never seen came out for each filesystem: "adding dirhash hint to filesystem".
In the words of Carol Cleveland: "What on earth does that mean?"
saw the same - googled that exact message - there are lots of posts on this from many different distros
one hint: take a look at /etc/fstab
haven't sorted it out yet - I tried one fstab suggestion of deleting trailing spaces and lines - got a warning that I hadn't left a trailing line when it was shutting down for a reboot, but it came back up with no warnings
Claude Jones wrote:
one hint: take a look at /etc/fstab
My fstab hasn't changed.
haven't sorted it out yet - I tried one fstab suggestion of deleting trailing spaces and lines
Why would you do this?
Anyway, I think it's part of the autofs update. What it /does/, I don't know. However, it was my impression that adding the dirhash hint was a one-time operation to update the fs.
Matt Flaschen
On Sat August 25 2007, Matthew Flaschen wrote:
haven't sorted it out yet - I tried one fstab suggestion of deleting trailing
spaces and lines
Why would you do this?
Read what I said, Matthew - I was trying out a suggestion
Anyway, I think it's part of the autofs update. What it /does/, I don't know. However, it was my impression that adding the dirhash hint was a one-time operation to update the fs.
Perhaps, but 'impressions' are not very precise diagnostic data - My fstab now looks like this:
***************************************** # /etc/fstab: static file system information. # # <file system> <mount point> <type> <options> <dump> <pass>
devpts /dev/pts devpts gid=5,mode=620 0 0 tmpfs /dev/shm tmpfs defaults 0 0 proc /proc proc defaults 0 0 sysfs /sys sysfs defaults 0 0 #Entry for /dev/sda3 : LABEL=/ / ext3 defaults 1 1 #Entry for /dev/sda1 : LABEL=boot /boot ext3 defaults 1 2 #Entry for /dev/sdc1 : LABEL=/home /home ext3 defaults 1 2 #Entry for /dev/sdd1 : LABEL=bigstore /home/cj/archive ext3 defaults 1 2 #Entry for /dev/sdb1 : LABEL=satatray /home/cj/sataext ext3 defaults 1 2 /dev/sde1 /media/80GB_mini_external ntfs-3g defaults,locale=en_US.UTF-8 0 0 #Entry for /dev/sda2 : LABEL=SWAP-sda2 swap swap defaults 0 0
#LABEL=archive500gb /home/cj/archive ext3 defaults 1 2 ********************************************
the hash'ed lines, save the three at the beginning, were added -- there seems to be some updating and some descriptive behavior involved here; in any event, on my system, all is well and this seems to have had no ill effect
On Sat, 2007-08-25 at 10:03 -0400, Claude Jones wrote:
Perhaps, but 'impressions' are not very precise diagnostic data - My fstab now looks like this:
#Entry for /dev/sda3 : LABEL=/ / ext3 defaults 1 1
the hash'ed lines, save the three at the beginning, were added -- there seems to be some updating and some descriptive behavior involved here; in any event, on my system, all is well and this seems to have had no ill effect
I saw the dirhash message, too, during bootup. Had a Google around, saw someone else say something similar, I wondered if this new unexplained "dirhash" was simply the informational comments after a hash mark being added to the fstab file. However, my fstab file is unchanged.
e.g. The entries are just a list like this, one per mount point: LABEL=donga/home /home ext3 defaults 1 2
Now I'm wondering if dirhash means adding some sort of checksum to a filing system. "Hash" being a term that I've heard used to describe a checksum (they do look like a wierd hash-up of characters jumbled together).
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
Tim wrote:
Now I'm wondering if dirhash means adding some sort of checksum to a filing system.
No. It's really not as mysterious as this thread makes it sound.
The ext3 and ext4 filesystems have a flag called "dir_index". You can enable it using tune2fs for quite some time. It's a feature that was introduced after ext3 was first released and because of this (and the fact that new features have to be tested first) it is not enabled by default by older releases.
Times apparently changed. The "Adding dirhash hint to *" message comes from e2fsck, the file system integrity checker for these types for filesystem. It found the feature is not enabled and now that it is stable enough it makes sense to enable it unconditionally. So it did and warned the user about it.
This feature, just as the tune2fs man page says, speeds up searching in large directories. With the traditional mechanism finding a file in a large directory is a linear process: files entries are looked at one by one until the right one is found. With dir_index enabled a hash table is used which allows to find each file in a constant time, potentially significantly speeding up the file lookup.
So, nothing devious is going on. It's just that the maintainers of the tools know that most people do not know about the new features and/or will not enable new features on their own for fear. This is why e2fsck does it by itself for safe options.
- -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
On Sunday August 26 2007 12:33:32 pm Ulrich Drepper wrote:
So, nothing devious is going on. It's just that the maintainers of the tools know that most people do not know about the new features and/or will not enable new features on their own for fear. This is why e2fsck does it by itself for safe options.
Nice detective work. I wouldn't have thought to read those man pages. The warnings were phrased in such a way as to raise alarm-bells, so I did some minimal investigating - minimal because there was no detectable downside after my machine came back up. Thanks for clearing that up.