10

I was reading trough the link on journaling-filesystems and i would like to know where exactly is the journal stored in my Harddisk.

Some pointers on this image shown below
alt text

Thanks,
Sen

9

The journal is stored in a separate space of the partition, you cannot access it directly. You can use sudo debugfs /dev/sda# where the # symbol is the number of your partition, and then using logdump in debugfs to print it out. The output is confusing though.

Generally, as a regular user, you don't need to know about the journal. Using ext3/4 will be sufficient to prevent data loss (in most cases).

This link might help: http://www.linuxforums.org/forum/red-hat-fedora-linux/121074-ext3-journal.html

  • I just wanted to know, as it was stated in the link, what is this on-disk journal? Where is it in the HDD? That picture was a bit confusing to me. – Sen Nov 25 '10 at 9:35
11

There is no fixed place for the journal, each filesystem stores it in a different place.

If you are expecting it to be a regular file, then your are mistaken, it's more like a part of the filesystem structure like the inode table. The funny point is that ext3/4 treats it exactly like a regular file. It is usually found in the inode number 8, but this is a kernel parameter that can be changed at compile time.

If you want to get technical, this article by Carlo Wood, written in March 2008, is a great read about the ext3 structure.

If you don't mind put journal in a place with words like partition table, inode or block and don't worry about it:

  • Good comment.. would like to vote up but lack of points.. :-) – Sen Nov 25 '10 at 9:39
  • "It is usually found in the inode number 8", can you explain briefly on this to me? – Sen Nov 25 '10 at 9:40
  • yup.. i found it.. it is the inode number of the Journal file.. – Sen Nov 25 '10 at 9:45
  • An inode is the record for an item in the filesystem, which could mean a file, a directory, a symbolic link, or something internal that the user doesn't need to know about - in this case the journal is an inode in ext3/4 (this is not necessarily the case in other filesystems). The inode record is referred to be a unique number. The inode record does not store the file's data itself - or specific metadata such as the filename, but points to such data. – thomasrutter May 18 '18 at 1:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.