Questions tagged [filesystems]

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

Filter by
Sorted by
Tagged with
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 ...
313
votes
1answer
234k 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.
17
votes
2answers
6k views

What are the different ways to set file permissions etc on gnu/linux

On Unix, a long time back, I learned about chmod: the traditional way to set permissions, on Unix (and to allow programs to gain privileges, using setuid, setgid). I have recently discovered some ...
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 ...
37
votes
5answers
18k views

The merits of a partitionless filesystem

I ran into something a couple of weeks ago that I'd never seen before: A filesystem (ext3 I believe) installed to a storage device without a partition. In essence /dev/sdb was the entire filesystem. I ...
147
votes
4answers
261k 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....
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 ...
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% ...
15
votes
3answers
11k views

ext4: How to account for the filesystem space?

I've recently formatted a 1.5 TB drive with the intention of replacing ntfs with ext4. Then I noticed that the files I saved don't fit on the new partition. df: ext4 (ext3 & ext2 show the same ...
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 ...
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?
433
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 ...
123
votes
5answers
119k 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, ...
32
votes
2answers
33k 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 correct:...
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" ...
31
votes
3answers
17k 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 ...
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 ...
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 ...
16
votes
3answers
7k views

Find filesystem of an unmounted partition from a script

I'm writing a custom automated install using AIF (Arch Installation Framework), and I need to find the filesystem on a partition given a partition. So far I have this: grok_partitions () { local ...
15
votes
3answers
14k views

Why are filenames that start with a dot hidden? Can I hide files without using a dot as their first character?

Initially I thought it was a coincidence, but now I see there's even a tag for it: all hidden file names start with a dot. Is this a convention? Why was it chosen? Can it be changed? Or in other words ...
7
votes
1answer
632 views

du results on filesystem inconsistent with df

What explains the discrepancy in usage (82 GB vs 13 GB) that I see below? Using df: $ df -h / Filesystem Size Used Avail Use% Mounted on /dev/sda2 96G 82G 9.9G 90% / ...
628
votes
3answers
284k 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?
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 ...
144
votes
4answers
620k 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 ...
34
votes
9answers
4k views

How to tell what type of filesystem you're on?

Is there a command to tell what type of filesystem you're using?
19
votes
1answer
32k views

Difference between block size and cluster size

I've got a question concerning the block size and cluster size. Regarding to what I have read about that I assume the following: The block size is the physical size of a block, mostly 512 bytes. ...
29
votes
3answers
3k views

How does Unix keep track of a user's working directory when navigating the file system?

Say I log into a shell on a unix system and begin tapping away commands. I initially begin in my user's home directory ~. I might from there cd down to the directory Documents. The command to change ...
32
votes
2answers
13k 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 ...
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 ...
28
votes
1answer
1k views

When did directories stop being readable as files?

I have the 1st edition of The Unix Programming Environment book. In chapter 2, the authors state that directories are readable as files, and mention some facts about the format of these files. They ...
9
votes
3answers
15k views

file block size - difference between stat and ls

I've noticed that when I do a: ls -ls file It provides block count, say 8 blocks. When I do: stat file I notice that the block count is 16, twice the number given by ls. The block size on my ...
12
votes
3answers
3k views

A virtual file containing the concatenation of other files

Is there a way of creating a filesystem object akin to this: mknod files p cat file1 file2 ... fileN > files but such that it can be seeked in, as if it were a regular file?
4
votes
4answers
8k views

How to recover a file just deleted [duplicate]

I just deleted a file in Nautilus with Shift+Delete, which warned me that "If you delete an item, it will be permanently lost." I wonder if there is no way to recover the file? My OS is Ubuntu 10.10.
2
votes
5answers
3k views

How does one inspect the directory structure information of a unix/linux file?

In Unix file systems directories are just special files with special directory structures that hold the child filename, filename size and inode reference number. The actual file metadata beyond ...
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 ...
71
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 ...
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?
16
votes
3answers
16k views

Extend a LUKS encrypted partition to fill disk

I recently upgraded my disk from a 128GB SSD to 512GB SSD. The / partition is encrypted with LUKS. I'm looking for help extending the partition to use all the free space on the new disk. I've ...
40
votes
4answers
6k views

Append huge files to each other without copying them

There are 5 huge files ( file1, file2, .. file5) about 10G each and extremely low free space left on the disk and I need to concatenate all this files into one. There is no need to keep original files,...
8
votes
3answers
90k views

How to repair a corrupted HFS+ partition from a damaged hard-disk?

I have a friend's Mac OS X disk that comes with an HFS+ partition. I am supposed to recover the personal data from this disk, and I'm not yet sure if the filesystem is corrupted or the disk is dying). ...
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 ...
107
votes
3answers
143k 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?
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?
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 ...
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 ...
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/...
14
votes
2answers
663 views

How can I be sure that a directory or file is actually deleted?

I know that most files, when deleted, aren't actually removed from the disk, and can be recovered later. How can I ensure that a directory I had deleted will actually be removed from the disk? Are ...
13
votes
2answers
2k views

Why is df missing 500MB of available space? [duplicate]

I've just had a message today from Ubuntu 11.04 that I have only 100 MB left, so I cleaned up some files, and I got 200 MB. Then, after a couple of hours, suddenly I have only 26 MB?! I tried df, du ...
6
votes
2answers
2k views

mount options shown in /proc/mounts

IIRC then the mount options shown in /proc/mounts have changed. Some time ago acl and user_xattr were shown, now it seems that only noacl and nouser_xattr are shown if these features are turned off. ...