Linux limit directory size

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Directory size limit [closed]
2 Answers 2
Maximum number of files/directories on Linux?
6 Answers 6
How to set a file size limit for a directory?
1 Answer 1
Why the size of an empty directory in Linux is 4KB? [closed]
2 Answers 2
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Directory size limit [closed]

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Closed 7 years ago .

In Linux, it’s possible to limit the size of a partition, for example with quota. But does a way to limit directory size exist? For example, I have a directory, let say /mnt/foo/bar , which is not a partition(e.g. not in df result). Is it possible? No mkfs possible on this directory.

2 Answers 2

Not directly, you could create a file of the size that you want to limit the directory to and then mount it using a loop mount into the tree.

Create a file to use as a filesystem e.g.
- fallocate -l 100M disk.img ( this isn’t always compatible with an underlying FS.)
- dd if=/dev/zero of=disk.img count=512k
create a filesystem on the disk image
- mkfs disk.img
mount the image
- mount -o loop disk.img /path/to/mount/point (optionally you can enable quotas too)

What you are asking for would be a nice feature, but I am not aware of any file system with such a feature. The best approximation without adding more file systems would be to use quotas, which limit storage space per user (or group).

One problem with doing it per directory is that the semantics are not going to be obvious, once you consider the possibility that a file may be hardlinked.

Consider the following sequence of events:

Administrator configure a system with 1GB quota per home directory
user1 run a program, which creates a logfile in

user1
When the logfile is 1MB large user2 creates a hardlink in

user2
user2 adds 900MB of other files to

user2

user1 appends 900MB of data to the logfile

user1 deletes the logfile from

There is not any one single of the above operations, you would expect to fail due to quota limits. Yet the outcome is that user2 is way above quota in the end.

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Maximum number of files/directories on Linux?

I’m developing a LAMP online store, which will allow admins to upload multiple images for each item.

My concern is — right off the bat there will be 20000 items meaning roughly 60000 images.

What is the maximum number of files and/or directories on Linux?

What is the usual way of handling this situation (best practice)?

My idea was to make a directory for each item, based on its unique ID, but then I’d still have 20000 directories in a main uploads directory, and it will grow indefinitely as old items won’t be removed.

Thanks for any help.

6 Answers 6

ext[234] filesystems have a fixed maximum number of inodes; every file or directory requires one inode. You can see the current count and limits with df -i . For example, on a 15GB ext3 filesystem, created with the default settings:

There’s no limit on directories in particular beyond this; keep in mind that every file or directory requires at least one filesystem block (typically 4KB), though, even if it’s a directory with only a single item in it.

As you can see, though, 80,000 inodes is unlikely to be a problem. And with the dir_index option (enablable with tune2fs ), lookups in large directories aren’t too much of a big deal. However, note that many administrative tools (such as ls or rm ) can have a hard time dealing with directories with too many files in them. As such, it’s recommended to split your files up so that you don’t have more than a few hundred to a thousand items in any given directory. An easy way to do this is to hash whatever ID you’re using, and use the first few hex digits as intermediate directories.

For example, say you have item ID 12345, and it hashes to ‘DEADBEEF02842. ‘ . You might store your files under /storage/root/d/e/12345 . You’ve now cut the number of files in each directory by 1/256th.

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How to set a file size limit for a directory?

I have a directory on my system which is used for a specific reason by applications and users, but I don’t want its size to be allowed to exceed 2GB, is there a way of setting up some sort of limit which just doesn’t allow the file size to exceed that or any other amount I decide to set for it in the future?

When the size limit is exceeded it should undo the last change (though there should be an option to have it so that it just stops the operation and doesn’t care if half a file was copied and left there) and then display a warning to the user.

I am running Ubuntu GNOME 16.10 with GNOME 3.22.

1 Answer 1

Usual filesystem quota on ext4 is per-user/group, not per-directory. ZFS can sort-of set a directory quota, by creating a filesystem of a fixed size off a ZFS volume. A simple trick, though, is to create a 2GB file, create a filesystem on it, and mount it at the desired folder:

In any case, filesystem quotas (or methods like this) aren’t as user friendly as you want. This method is one-way flexible, in that you can increase the size online, but decreasing it would be hard.

touch : touch 2gbarea creates an empty file named 2gbarea .
truncate : truncate is used to resize files (in this case, I resize the currently empty 2gbarea file to 2 GB using -s 2G ).
mke2fs : mke2fs creates ext2/3/4 filesystems (in this case, ext4).
mount mounts the filesystem on the given directory.
df is used to list filesystem usage.

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Why the size of an empty directory in Linux is 4KB? [closed]

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Closed 6 years ago .

I’m using Ubuntu 14.04 and I made an empty directory on /tmp with the mkdir command:

and then I checked it’s size using ls:

and the result shows that the size of the directory is 4KB, although it has nothing inside!

then I created an empty file with touch:

and then I checked its size:

the result shows that the empty file is of 0B, which differs from the empty directory.

I’ve read about some Q&A’s saying that the 4KB is the metadata of the directory. But if it is the metadata, what kind of information is stored inside and why it is so huge, and why an empty file don’t have such kind of metadata? If it is not the metadata, what does the 4KB mean?

2 Answers 2

I’m going to break this question down into 3 parts, 2 of which I can answer.

Part 1: why isn’t an empty directory size 0?

Because it contains . and .. so it’s not really empty.

Part 2: Why is 4K the minimum?

Because that’s the filesystem’s block size. You can set it smaller when you create the filesystem, but there is overhead. The filesystem must remember a free-or-in-use flag for every block, so smaller blocks = more blocks = more overhead. (In the early days of ext2, the default block size was 1K. Disks were small enough that the space saved by not allocating a multiple of 4K for every file was more important than the space used for the free block map.)

Block sizes over 4K aren’t possible because 4K is the page size (the smallest unit of virtual memory) on most processors, and Linux wasn’t designed to deal with filesystem blocks bigger than memory pages.

Part 3: When you ls -l a regular file, you get the actual number of bytes used but when you ls -ld a directory, you get the number of bytes allocated. Why?

This part I don’t know. For regular files, there is an allocation size you can view with ls -s , and the two sizes actually tell you different things. But on directories, the -l size is like a redundant copy of the -s size. Presumably the kernel could report a size that indicates how much of the 4K block is actually used, but it doesn’t. I don’t know why.

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16 GiB) 2048 GiB (= 2 TiB) ext2/3 with 2 KiB blocksize 256 GiB 8192 GiB (= 8 TiB)

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