In Linux in a Folder there are many files, all created with fallocate with random size. How to find files whose size is not divisible by 4096 and correct the filesize (rounded up) to a multiple of 4096? They can be found with : find . -type f -printf '%s\t%p\n' | awk -F'\t' '{size=$1; file=$2; if (size % 4096 != 0) print file}' But how to size them up that the filesize is divisible by 4096 ?

So my setup is like this. $ truncate -s 1T volume $ losetup -f --show volume /dev/loop0 $ mkfs.ext4 /dev/loop0 $ ls -sh volume 1.1G volume $ mount /dev/loop0 /mnt/loop Now I have a 1.1TB volume, as expected. The overhead of ext4 expanded the sparse file to 1.1G, but that's fine. Now to add a file. $ dd if=/dev/urandom of=/mnt/loop/file bs=1M count=10240 $ ls -sh volume 12G volume Cool, now I don't want the file. $ rm /mnt/loop/file $ ls -sh volume 12G volume The free space is still taking up space, as expected, and $ fallocate -d volume frees up 1gb. My question is, how can I zero out the free space here without expanding the volume to the full size? $ dd if=/dev/zero will expand it to full size, and with conv=sparse makes it create a useless sparse file inside the volume. TL;DR: Is there a way to make losetup ignore writes of null blocks to null sectors, while allowing everything else?

I am using a Linux system, and I want to create a file using fallocate. Not a full sized file, I just want to allocate the size I choose on the file system. I have the size value in temp/size and the name value in temp/name, and will store the file in temp/decrypt/. I tried this: fallocate -l $(cat temp/size) temp/decrypt/"$(cat temp/name)" but it fails with:

fallocate failed: Operation not supported

I don't know what is wrong. $ cat temp/size 1073741824 and $ cat temp/name testname123.data This works, but where is the error?

When is executed the sudo fallocate -l 2G /swapfile command, then 2 GB is created, but with that kind of content or data? Can be it customized? If yes How?. I did do some research but there are no details about this. I want to know if is good use fallocate for swap file purpose. For example sudo dd if=/dev/zero of=/swapfile bs=1024 count=N creates the data filled with Zeros, not sure if swap file asks for mandatorily the data with zeros - in the swap file tutorials did not mention of this.

I created a file to mount as /tmp dir to limit it's size so it cant crash the system. I used mkfs.ext4 on it and it mounts in /etc/fstab. Now I need to increase the size, so I used fallocate again, and the /tmpfile shows larger now, but when mounted is the same size. I tried a bunch of things, like mounting manually and using resize2fs on the unmounted file and the mounted dir. The former has no errors, but still isnt larger, even after running the suggested e2fsck -f /tmpfile on it. Any ideas? I'm not using a loop device as with this answer, nor 2 partitions formated with parted. https://unix.stackexchange.com/questions/595641/how-to-increase-the-size-of-a-loop-virtual-disk EDIT: As pointed out, mounting a file to a directory uses a loop device by default, even without the mount -o loop option. Using fallocate -l 200M /tmpfile and then resize2fs /dev/loop# worked with the file mounting edited out of the /etc/fstab, rebooting, and then mounting it over the bootup /tmp to check the size, by undoing the fstab edit and using mount -a. Sidenote, I could have mounted it to /mnt to check, but unix/linux deals with overmounting gracefully: https://unix.stackexchange.com/questions/198542/what-happens-when-you-mount-over-an-existing-folder-with-contents , though it seems there could be more conflicts when overmounting the home directory, but perhaps not.

If we create a swapfile with fallocate we are told that the file contains holes and therefore the operation is halted. **What are these holes?** - Is it unallocated disk space, which makes the whole file allocation a hole itself? Like this: - block1 -> empty - block2 -> empty - block3 -> empty or - is it the blocks preallocated contains holes in between, and therefore they are not contiguous? Like this: - block1 - block2 - hole in block3 [occupied by other file in the disk] - block4 **Test** fallocate -l 100MB /swap chmod 600 /swap mkswap /swap swapon /swap **Output** swapon: swapfile has holes swapon: /swap: swapon failed: Invalid argument

I want to have a LUKS volume as a loopback device pointing at a sparse file. Lets say I put a 20gb file on it, then later I delete it. How can I zero that area on the device itself so I can fallocate -d the loopback file to reclaim the space?

Why fallocate -c -l1GiB **once** cause the second loop of dd speed decrease from 1.0 GB to ~200 MB/s ? xb@dnxb:~/Downloads/test$ fallocate -l 10.2GiB lala.mp4 xb@dnxb:~/Downloads/test$ ls -larthiF --context --color total 11G 41680908 drwxr-xr-x 121 xiaobai xiaobai ? 100K Dis 3 01:36 ../ 53086804 drwxrwxr-x 2 xiaobai xiaobai ? 4.0K Dis 3 01:36 ./ 53086805 -rw-rw-r-- 1 xiaobai xiaobai ? 11G Dis 3 01:37 lala.mp4 xb@dnxb:~/Downloads/test$ f='lala.mp4'; n=0; while (( "$(stat --printf="%s" $f)" > 1073741824 )); do ((n++)); echo "[dd...$n]"; dd bs=1G skip=0 count=1 if=$f of="$f.$n"; fallocate -c -l1GiB $f; done; ((n++)); mv $f $f.$n; [dd...1] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.05744 s, 1.0 GB/s [dd...2] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 3.24091 s, 331 MB/s [dd...3] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.56858 s, 235 MB/s [dd...4] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.02249 s, 267 MB/s [dd...5] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.34307 s, 247 MB/s [dd...6] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.27371 s, 251 MB/s [dd...7] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.80721 s, 223 MB/s [dd...8] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.17114 s, 257 MB/s [dd...9] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.60627 s, 233 MB/s [dd...10] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.13853 s, 259 MB/s xb@dnxb:~/Downloads/test$ xb@dnxb:~/Downloads/test$ ls -larthiF --context --color total 11G 41680908 drwxr-xr-x 121 xiaobai xiaobai ? 100K Dis 3 01:36 ../ 53086806 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:37 lala.mp4.1 53086807 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:37 lala.mp4.2 53087049 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:37 lala.mp4.3 53087910 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:37 lala.mp4.4 53087911 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:37 lala.mp4.5 53087913 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:38 lala.mp4.6 53087914 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:38 lala.mp4.7 53087962 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:38 lala.mp4.8 53087963 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:38 lala.mp4.9 53087964 -rw-rw-r-- 1 xiaobai xiaobai ? 1.0G Dis 3 01:39 lala.mp4.10 53086805 -rw-rw-r-- 1 xiaobai xiaobai ? 200M Dis 3 01:39 lala.mp4.11 53086804 drwxrwxr-x 2 xiaobai xiaobai ? 4.0K Dis 3 01:39 ./ xb@dnxb:~/Downloads/test$ **[Update]** I noticed added sync before next dd will make it consistent again (sleep 120 also work, but not sleep 20), but the total time will slower since sync take more time than **dd without sync**: xb@dnxb:~/Downloads/test$ f='lala.mp4'; n=0; while (( "$(stat --printf="%s" $f)" > 1073741824 )); do ((n++)); echo "[dd...$n]"; dd bs=1G skip=0 count=1 if=$f of="$f.$n"; fallocate -c -l1GiB $f; sync; done; ((n++)); mv $f $f.$n; [dd...1] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.904357 s, 1.2 GB/s [dd...2] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.902471 s, 1.2 GB/s [dd...3] 1+0 records in 1+0 records out 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.896056 s, 1.2 GB/s ...

I totally understand that --dig-holes creates a sparse file in-place. That is, if the file has holes --dig-holes options removes those holes: Let's take it in a very simplified way, let's say we have a huge file named non-sparse: *non-sparse:* aaaaaaaaaaaaaaaaaaaaaaaaaaaa \x00\x00\x00\x00\x00\x00\x00 \x00\x00\x00\x00\x00\x00\x00 \x00\x00\x00\x00\x00\x00\x00 bbbbbbbbbbbbbbbbbbbbbbbbbbbb \x00\x00\x00\x00\x00\x00\x00 \x00\x00\x00\x00\x00\x00\x00 cccccccccccccccccccccccccccc *non-sparse* has many zeros in it, assume that the interleaving zeros are in Gigabytes. fallocate --dig-holes de-allocates the space available for the zeros (holes) where the actual file size remains the same (preserved). Now, there's --punch-hole what does it really do? I read the man page, still don't understand: -p, --punch-hole Deallocates space (i.e., creates a hole) in the byte range starting at offset and continuing for length bytes. Within the specified range, partial filesystem blocks are zeroed, and whole filesystem blocks are removed from the file. After a successful call, subsequent reads from this range will return zeroes. Creating hole, that's the opposite of --dig-hole option it seems like that, and how come that digging a hole isn't the same as creating a hole?! Help! we need a logician :). The naming of the two options are synonymous linguistically which perhaps makes confusion. What's the difference between --dig-holes and --punch-holes operationally (not logically or linguistically please!)?