A filesystem is a method of storing and organizing computer files and their data.
130
votes
3answers
21k views
What is the purpose of the lost+found folder in Linux and Unix?
There is a folder at the root of Linux and Unix operating systems called /lost+found/
What is it for? Under what circumstances would I interact with it? How would I interact with it?
65
votes
4answers
6k views
/usr/bin vs /usr/local/bin on Linux
Why are there so many places to put a binary in Linux? There are atleast these five:
/bin/
/sbin/
/usr/bin/
/usr/local/bin/
/usr/local/sbin/
And on my office box, I do not have write permissions ...
38
votes
2answers
1k views
Why does '/' have an '..' entry?
This just baffles me. Why does the root directory contain a reference to a parent directory?
bob@bob:/$ ls -a
. build home lib32 mnt .rpmdb sys vmlinuz
.. cdrom ...
30
votes
7answers
1k views
ZFS under linux, does it work?
Could I get ZFS to work properly in Linux?
Are there any caveats / limitations?
29
votes
2answers
7k views
Why hard links not allowed to directories in UNIX/Linux
I read in text books that UNIX/Linux doesn't allows hard links to directories but soft links do. Is it because, when we have cycles and if we create hardlinks, and after some time we delete the ...
27
votes
5answers
15k views
What is a Superblock, Inode, Dentry and a File?
From the article Anatomy of Linux File Systems by Tim Jones, I read that Linux views all the file systems from the perspective of a common set of objects and these objects are superblock, inode, ...
26
votes
5answers
7k views
Can I configure my Linux system for more aggressive file system caching?
I am neither concerned about RAM usage (as I've got enough) nor about losing data in case of an accidental shut-down (as my power is backed, the system is reliable and the data are not critical). But ...
26
votes
2answers
832 views
Why is '.' a hard link in Unix?
I've seen many explanations for why the link count for an empty directory in Unix based OSes is 2 instead of 1. They all say that it's because of the '.' directory, which every directory has pointing ...
23
votes
3answers
1k views
Why are text files 4kB?
For some reason, when I make a text file on OS X, it's always at least 4kB, unless it's blank. Why is this? Could there be 4,000 bytes of metadata about 1 byte of plain text?
23
votes
1answer
1k views
Why does “ls *” take so much longer than “ls”?
I have a couple of files in a directory:
$ ls | wc -l
9376
Can anybody explain why there is such a huge time difference in using ls * and ls?
$ time ls > /dev/null
real 0m0.118s
user ...
21
votes
1answer
778 views
What do the device files in /dev actually do?
(Not a duplicate of Understanding /dev and its subdirs and files)
I was browsing around my filesystem and for the first time I took a second to analyze my /dev directory. I was surprised by the ...
20
votes
2answers
2k views
what is this new filesystem /run?
I just ran df -h a minute ago and noticed a filesystem has been added that I'm not familliar with. Does anyone know why /run exists? is this something that's
been added by the kernel? by Arch Linux?
...
19
votes
1answer
778 views
Purpose of /dev/zero?
I tried to cat /dev/zero, and it didn't seem to do anything. I googled /dev/zero, and it says it's basically a blank file with infinite size. Is cat printing an infinite number of non-existent ...
19
votes
6answers
17k views
Mount Google Drive in Linux?
Now that Google Drive is available, how do we mount it to a Linux filesystem? Similar solutions exist for Amazon S3 and Rackspace Cloud Files.
19
votes
5answers
5k views
How can I create a /dev/null-like “blackhole” directory?
I would like to create a "/dev/null" directory (or a "blackhole" directory) such that any files written to it are not really written, but just disappear.
I have an application that writes out large ...
18
votes
2answers
879 views
Where do the files go if you mount a drive to a folder that already contains files?
I just accidentally mounted a new drive to a folder that already contained files. I don't care about them and have them somewhere else, but that folder appears empty now. I'm curious what happened ...
18
votes
2answers
3k views
What mount points exist on a typical Linux system?
I have 2 questions.
During Linux installation we specify memory space for 2 mount points - root and swap. Are there any other mount points created without the users notice?
Is this statement ...
17
votes
5answers
2k views
Why do hard links exist?
I know what hard links are, but why would I use them? What is the utility of a hard link?
17
votes
4answers
11k views
Reserved space for root on a filesystem - why?
I understand that by default, newly created filesystems will be created with 5% of the space allocated for root. I also know you can change the defined space with:
tune2fs -m 1 /dev/sdXY
What I'm ...
17
votes
4answers
662 views
What doesn't need defragmentation? Linux or the ext2 ext3 FS?
Why don't you have to defrag a Linux system? Because it's using the ext2/ext3 file system or because it's Linux?
That's relevant, because a have a double boot system (W7 / Ubuntu) and a common ...
16
votes
4answers
12k views
Recovering ext4 superblocks
Recently, my external hard drive enclosure failed (the hard drive itself powers up in another enclosure). However, as a result, it appears its EXT4 file system is corrupt.
The drive has a single ...
15
votes
3answers
1k views
File system for an SSD drive
I always thought that traditional file systems, are geared and optimized for non-ssd drive, where, for instance, data locality is important, and fragmentation is problematic.
Is there a file system ...
15
votes
2answers
228 views
How does “rm” on a NTFS filesystem differs from Windows' own implementation?
I have an external USB disk with an NTFS filesystem on it.
If I remove a file from Windows and I run one of the several "undelete" utilities (say, TestDisk) I can easily recover the file (because ...
14
votes
8answers
544 views
How to tell what type of filesystem you're on?
Is there a command to tell what type of filesystem you're using?
14
votes
3answers
1k views
Is there a limit of hardlinks for one file?
Is there a limit of number of hardlinks for one file? Is it specified anywhere? What are safe limits for Linux? And what for other POSIX systems?
13
votes
3answers
1k views
How can I de-fragment a drive using Ubuntu?
Is it necessary to defrag drives in Ubuntu? If so, how do I do it and how often should it be done?
13
votes
5answers
1k views
Do journaling filesystems guarantee against corruption after a power failure?
I am asking this question on behalf of another user who raised the issue in the Ubuntu chat room.
Do journaling filesystems guarantee that no corruption will occur if a power failure occurs?
If this ...
13
votes
5answers
2k views
What's the most “correct” mount point for a permanent NTFS partition?
I have an NTFS partition (containing a Windows installation from which I dual boot) that I would like to permanently mount from my Linux installation. Problem is, I can't figure out what the ...
13
votes
3answers
324 views
When does `ls -s` print “0”
Of course, the standard way of testing if a file is empty is with test -s FILE, but one of our clients have received a script containing tests like this:
RETVAL=`ls -s ./log/cr_trig.log | awk '{print ...
13
votes
1answer
5k views
How can I increase the number of inodes in an ext4 filesystem?
I had a problem (new to me) last week. I have a ext4 (Fedora 15) filesystem. The application that runs on the server suddenly stopped. I couldn't find the problem at first look.
df showed 50% ...
13
votes
3answers
262 views
Securely delete files on btrfs filesystem
Sometimes, there's the need to delete a file in a filesystem, and make sure that the file is truly gone. A file that contains sensitive passwords, for example, should be throughly wiped from the disk.
...
13
votes
3answers
261 views
Horrible situation - file systems mounted simultaneously by multiple independent OS instances
How do I get out of this situation safely?
Details are as follow:
A xen server has got block devices allocated to VMs. But these devices have also been mounted inside Xen.
In fact 44 of these ...
12
votes
3answers
639 views
File system compatible with all OSes?
I use Linux and Mac OS X on a regular basis, and sometimes I have to use Windows. I need to use a flash drive on all three, and I need a filesystem that will work well on all of them. None of the ...
12
votes
1answer
7k views
How do I find on which physical device a folder is located?
Specifically: I did sudo mkdir /work, and would like to verify it indeed sits on my harddrive and not mapped to some other drive.
How do I check where this folder is physically located?
12
votes
3answers
660 views
Where do open file handles go when they die?
What happens to the files that are deleted while they have a file handle open to them?
I have been wondering this ever since I figured out I could delete a video file while it was playing in MPlayer ...
12
votes
2answers
3k views
What is the difference between procfs and sysfs?
What is the difference between procfs and sysfs? Why are they made as file systems? As I understand it, proc is just something to store the immediate info regarding the processes running in the ...
11
votes
6answers
1k views
Which extension to use for text files? (Unix/Linux)
I noticed that I can read text files without an extension .txt just fine. How come? Should I save these files with or without the .txt extension?
Also, what about .ini files? I usually use them like ...
11
votes
3answers
2k views
What are the advantages of Btrfs for end users?
Btrfs has begun to gain some momentum in replacing ext4 as the default filesystem of choice for a few distributions such as Fedora Core 16. It is experimentally available in a number of other ...
11
votes
3answers
1k views
Automatically rename files when they are placed in a specific directory
Is it possible to automatically rename a file when it's placed in a specific directory?
For example I have a directory named "dir0".I move or copy a file named "file1" to "dir0".then "file1" should ...
11
votes
2answers
375 views
Why is JFS so obscure?
When I first got into using Slackware years ago I quickly learned to love JFS over ext3 or reiserfs given that it was reliable and if there was an unclean shutdown, its disk checking was very very ...
11
votes
5answers
2k views
Is btrfs stable enough for home usage? [closed]
btrfs has finally found its way into the latest kernels, is it considered stable and safe enough to use in a home backup scenario (as an alternative to zfs) ?
11
votes
5answers
6k views
Script to monitor folder for new files?
How do I detect new files in a folder with a bash script? I would like to process the files as soon as they are created in the folder. Is this possible to do so or do I have to schedule a script with ...
11
votes
2answers
1k views
understanding “mount” as a concept in the OS
I want to understand what mounting is. It is used in different contexts and situations and I can't find resources which:
Describe the mount concept
Explain the actions taken by the ...
11
votes
2answers
1k views
How can I find the number of files on a filesystem?
I want to know how many files I have on my filesystem. I know I can do something like this:
find / -type f | wc -l
This seems highly inefficient. What I'd really like is to do is find the total ...
11
votes
2answers
7k views
timestamp, modification time, and created time of a file
I just know that ls -t, -f give different sorting of files and subdirectories under a directory.
Now I wonder what are the differences between timestamp, modification time, and created time of a ...
11
votes
6answers
2k views
Linux equivalent to ReadyBoost?
Is there a kernel module or some other patch or something similar to Windows' ReadyBoost?
Basically I'm looking for something that allows disk reads to be cached on a Flash drive.
11
votes
1answer
281 views
How to compact a directory
Every so often, some application runs wild and fills a directory with a huge amount of files. Once we fix the bug and clean up the files, the directory stays big (>50MB) even though there's only 20-30 ...
10
votes
5answers
913 views
Best way to do full disk encryption?
I have got a bit lost and am not sure which technology to choose for full disk encryption. It is hard to tell if the information out there is still up to date. Is there a current best practice ...
10
votes
3answers
1k views
What happens when you delete a hard link?
If you do rm myFile where myFile is a hard link, what happens?
10
votes
3answers
1k views
What file systems on Linux store the creation time?
Are there any (good known, reliable) file systems on Linux that store the creation time of files and directories in the i-node table?
If there are, is the "changed" time replaced by the creation ...
