Questions tagged [filesystems]

A filesystem is a way to organize and store computer files with their data.

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628
votes
3answers
283k 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?
432
votes
5answers
103k views

/usr/bin vs /usr/local/bin on Linux

Why are there so many places to put a binary in Linux? There are at least these five: /bin/ /sbin/ /usr/bin/ /usr/local/bin/ /usr/local/sbin/ And on my office box, I do not have write permissions to ...
312
votes
1answer
233k views

What is a bind mount?

What is a “bind mount”? How do I make one? What is it good for? I've been told to use a bind mount for something, but I don't understand what it is or how to use it.
181
votes
7answers
349k views

Find where inodes are being used

So I received a warning from our monitoring system on one of our boxes that the number of free inodes on a filesystem was getting low. df -i output shows this: Filesystem Inodes IUsed ...
147
votes
4answers
260k views

How does the sticky bit work?

SUID The sticky bit applied to executable programs flagging the system to keep an image of the program in memory after the program finished running. But I don't know that what it's stored in memory....
144
votes
4answers
618k views

How to get the complete and exact list of mounted filesystems in Linux?

I usually use mount to check which filesystems are mounted. I also know there is some connection between mount and /etc/mtab but I'm not sure about the details. After reading How to check if /proc/ is ...
130
votes
2answers
130k views

how can I recursively delete empty directories in my home directory? [duplicate]

Possible Duplicate: How to remove all empty directories in a subtree? I create directories very often, scattered over my home directory, and I find it very hard to locate and delete them. I want ...
128
votes
8answers
53k views

Why are hard links to directories not allowed in UNIX/Linux?

I read in text books that Unix/Linux doesn't allow hard links to directories but does allow soft links. Is it because, when we have cycles and if we create hard links, and after some time we delete ...
123
votes
5answers
118k views

What is a Superblock, Inode, Dentry and a File?

From the article Anatomy of the Linux file system by M. 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, ...
120
votes
10answers
230k views

Script to monitor folder for new files?

How to 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 ...
112
votes
6answers
97k 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 ...
111
votes
4answers
8k views

Why are there so many different ways to measure disk usage?

When I sum up the sizes of my files, I get one figure. If I run du, I get another figure. If I run du on all the files on my partition, it doesn't match what df claims is used. Why are there so many ...
107
votes
3answers
142k 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?
103
votes
4answers
100k 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 ...
102
votes
3answers
45k views

Can I watch the progress of a `sync` operation?

I've copied a large file to a USB disk mounted on a Linux system with async. This returns to a command prompt relatively quickly, but when I type sync, of course, it all has to go to disk, and that ...
100
votes
2answers
242k views

timestamp, modification time, and created time of a file

I just know that ls -t and ls -f give different sorting of files and subdirectories under a directory. What are the differences between timestamp, modification time, and created time of a file? How ...
96
votes
1answer
210k views

How to determine the filesystem of an unmounted device? [duplicate]

Possible Duplicate: Find filesystem of a partition from a script How to show the filesystem type via the terminal? I'm looking for a command that yields the filesystem type as mount would use/...
93
votes
5answers
220k views

Too many levels of symbolic links

I created this file structure: test/src test/firefox When I run this command: ln -s test/src test/firefox I would expect a symbolic link test/firefox/src to be created pointing to test/src, ...
90
votes
12answers
10k views

Why is Linux's filesystem designed as a single directory tree?

Can anyone explain why Linux is designed as a single directory tree? Whereas in Windows we can have multiple drives like C:\, and D:\, there is a single root in Unix. Any specific reason there?
85
votes
3answers
31k views

What happens when I run the command cat /proc/cpuinfo?

What happens when I write cat /proc/cpuinfo. Is that a named pipe (or something else) to the OS which reads the CPU info on the fly and generate that text each time I call it?
80
votes
2answers
222k views

How to show the filesystem type via the terminal? [duplicate]

Possible Duplicate: How to tell what type of filesystem you’re on? Find filesystem of an unmounted partition from a script How can I quickly check the filesystem of the partition? Can I do that ...
79
votes
5answers
37k views

Birth is empty on ext4

I was just reading up on the Birth section of stat and it appears ext4 should support it, but even a file I just created leaves it empty. ~ % touch test ...
78
votes
2answers
5k views

Why does '/' have an '..' entry?

This has always puzzled 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 ...
78
votes
2answers
63k views

What is this folder /run/user/1000?

What is this folder: /run/user/1000 on my Fedora system and what does it do? ~ $ df -h Filesystem Size Used Avail Use% Mounted on tmpfs 1.2G 20K 1.2G 1% /run/user/1000 EDIT: 7 ...
78
votes
5answers
35k 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 ...
77
votes
6answers
23k 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?
73
votes
6answers
86k views

Clear unused space with zeros (ext3,ext4)

How to clear unused space with zeros ? (ext3,ext4) I'm looking for something smarter than cat /dev/zero > /mnt/X/big_zero ; sync; rm /mnt/X/big_zero Like FSArchiver is looking for "used space" ...
73
votes
2answers
60k views

What is this new /run filesystem?

I just ran df -h a minute ago and noticed a filesystem has been added that I'm not familiar with. Does anyone know why /run exists? Is this something that's been added by the kernel? By Arch Linux? ...
70
votes
5answers
37k 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 ...
65
votes
10answers
69k 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.
63
votes
5answers
110k views

How can I edit symlinks?

My basic understanding of a symlink is as a special file, a file that contains a string path to another file. The kernel's VFS abstracts a lot of that away but is there any reason why symlinks seem to ...
60
votes
5answers
89k views

How do you make samba follow symlink outside the shared path

This is Ubuntu server 10.04 64 and samba 3.4.7. I have a shared directory /home/mit/share and another one /home/temp that I link into the shared one: ln -s /home/temp /home/mit/share/temp But on ...
58
votes
6answers
137k 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% ...
57
votes
3answers
55k views

What happens when you delete a hard link?

If you do rm myFile where myFile is a hard link, what happens?
56
votes
1answer
3k views

Change permisions of a file with my cat's help

root@system:~# less myfile -bash: /bin/less: Input/output error The root filesystem is dead. But my cat is still alive (in my memory): root@system:~# cat > /tmp/somefile C^d root@system:~# He's ...
55
votes
7answers
5k views

How are file types known if not from file suffix?

I would like to know how file types are known if filenames don't have suffixes. For example, a file named myfile could be binary or text to start with, how does the system know if the file is binary ...
55
votes
5answers
6k views

Are file edits in Linux directly saved into disk?

I used to think that file changes are saved directly into the disk, that is, as soon as I close the file and decide to click/select save. However, in a recent conversation, a friend of mine told me ...
51
votes
8answers
8k views

On Unix systems, why do we have to explicitly `open()` and `close()` files to be able to `read()` or `write()` them?

Why do open() and close() exist in the Unix filesystem design? Couldn't the OS just detect the first time read() or write() was called and do whatever open() would normally do?
51
votes
2answers
3k 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 ...
50
votes
3answers
20k views

understanding “mount” as a concept in the OS [duplicate]

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 computer/OS/...
49
votes
1answer
23k 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 ...
48
votes
5answers
64k views

How to safely turn off swap permanently and reclaim the space? (on Debian Jessie)

I installed Debian Jessie with default partitioning on my SSD drive. My current disk partitioning looks like this: As I have 16GB of RAM, I assume I don't need swap. But since I have other disk ...
47
votes
4answers
44k 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 ext'...
46
votes
3answers
15k 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?
45
votes
4answers
11k views

Is the slash (/) part of the name of the Linux root directory?

Is the slash (/) really part of the name of the Linux root directory? Or is it just a symbol for it? What about /etc and so on? Update Suppose /dev/sda2 is the block device of a Linux root ...
45
votes
3answers
97k views

CIFS vs SAMBA, What are the differences

What are the differences between CIFS and SAMBA? When would you use one over the other? Are there any performance differences between the two?
44
votes
2answers
97k views

Create and format exFAT partition from Linux

Is it possible to create and format an exFAT partition from Linux?
44
votes
10answers
32k views

Is there a file search engine like “Everything” in Linux?

On Windows there a nice file search engine called Everything, which is (unlike find) very fast and (unlike locate) always returns up to date results. AFAIK it works by filling a database from the ...
43
votes
3answers
7k views

Is an ISO image file a filesystem in its own right?

I am trying to understand what the relationship a xxx.iso file has to the other aspects of a block device, e.g. partitions and a file system. It's common for people to describe accessing or making a ....
43
votes
4answers
23k views

Way to instantly fill up/use up lots of disk space?

On a Linux VM I would like to TEST the NAGIOS monitoring more deeply than just switching off the VM or disconnecting the virtual NIC; I would like to test or "enforce a disk space alarm" through ...