I think a very useful and underrated Linux thing is being able to instantly create a file of any arbitrary size without physically having to write all those bytes. Dependent on file system of course.
`fallocate`
`fallocate`
November 10, 2024 at 9:15 PM
I think a very useful and underrated Linux thing is being able to instantly create a file of any arbitrary size without physically having to write all those bytes. Dependent on file system of course.
`fallocate`
`fallocate`
sudo fallocate --punch-hole panties
sudo touch panties
sudo rm panties
sudo rm panties
July 2, 2026 at 2:57 AM
sudo fallocate --punch-hole panties
sudo fallocate -l 100G /google-drive
December 3, 2025 at 7:30 PM
sudo fallocate -l 100G /google-drive
🚨 EUVD-2026-86955
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: invalidate fscache for fallocate range operations
smb3_zero_range(), smb3_pun...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-86955
#cybersecurity #infosec #cve #euvd
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: invalidate fscache for fallocate range operations
smb3_zero_range(), smb3_pun...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-86955
#cybersecurity #infosec #cve #euvd
September 25, 2026 at 12:04 PM
🚨 EUVD-2026-86955
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: invalidate fscache for fallocate range operations
smb3_zero_range(), smb3_pun...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-86955
#cybersecurity #infosec #cve #euvd
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: invalidate fscache for fallocate range operations
smb3_zero_range(), smb3_pun...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-86955
#cybersecurity #infosec #cve #euvd
Why do in 2 seconds what you can do with fallocate in 1 second?
March 17, 2025 at 6:49 PM
Why do in 2 seconds what you can do with fallocate in 1 second?
and honestly it just makes the code easier to reason about in general. we don't need to code golf every script!
(but also fallocate is better than dd for this usecase :P)
(but also fallocate is better than dd for this usecase :P)
October 5, 2023 at 2:05 PM
and honestly it just makes the code easier to reason about in general. we don't need to code golf every script!
(but also fallocate is better than dd for this usecase :P)
(but also fallocate is better than dd for this usecase :P)
hey util-linux, what's been going on with you lately?
util-linux: "addpart, blkdiscard, blkid, blkzone, blockdev, cal, cfdisk, chcpu, chfn, chmem, chrt, chsh, col, colcrt, colrm, column, commands.txt, ctrlaltdel, delpart, dmesg, eject, enosys, exch, fadvise, fallocate, fdformat, fdisk, fincore,
util-linux: "addpart, blkdiscard, blkid, blkzone, blockdev, cal, cfdisk, chcpu, chfn, chmem, chrt, chsh, col, colcrt, colrm, column, commands.txt, ctrlaltdel, delpart, dmesg, eject, enosys, exch, fadvise, fallocate, fdformat, fdisk, fincore,
May 28, 2025 at 4:01 AM
hey util-linux, what's been going on with you lately?
util-linux: "addpart, blkdiscard, blkid, blkzone, blockdev, cal, cfdisk, chcpu, chfn, chmem, chrt, chsh, col, colcrt, colrm, column, commands.txt, ctrlaltdel, delpart, dmesg, eject, enosys, exch, fadvise, fallocate, fdformat, fdisk, fincore,
util-linux: "addpart, blkdiscard, blkid, blkzone, blockdev, cal, cfdisk, chcpu, chfn, chmem, chrt, chsh, col, colcrt, colrm, column, commands.txt, ctrlaltdel, delpart, dmesg, eject, enosys, exch, fadvise, fallocate, fdformat, fdisk, fincore,
nemi, [05/05/2026 18:59]
...
this happen often?
decchi, [19:00]
well it was the main problem to set the flake up in the first place,
nemi, [19:00]
ah yea
decchi, [19:00]
had to do the fallocate and swapon thing so it didnt freeze
nemi, [19:01]
how do you make these utterly banal name so...
...
this happen often?
decchi, [19:00]
well it was the main problem to set the flake up in the first place,
nemi, [19:00]
ah yea
decchi, [19:00]
had to do the fallocate and swapon thing so it didnt freeze
nemi, [19:01]
how do you make these utterly banal name so...
May 5, 2026 at 10:12 PM
nemi, [05/05/2026 18:59]
...
this happen often?
decchi, [19:00]
well it was the main problem to set the flake up in the first place,
nemi, [19:00]
ah yea
decchi, [19:00]
had to do the fallocate and swapon thing so it didnt freeze
nemi, [19:01]
how do you make these utterly banal name so...
...
this happen often?
decchi, [19:00]
well it was the main problem to set the flake up in the first place,
nemi, [19:00]
ah yea
decchi, [19:00]
had to do the fallocate and swapon thing so it didnt freeze
nemi, [19:01]
how do you make these utterly banal name so...
if you have a linux computer and need for some reason to create an arbitrarily large empty file that isn't written to your disk you can run this in a terminal:
fallocate -l 10G detailed_evidence.img
fallocate -l 10G detailed_evidence.img
May 3, 2024 at 5:51 PM
if you have a linux computer and need for some reason to create an arbitrarily large empty file that isn't written to your disk you can run this in a terminal:
fallocate -l 10G detailed_evidence.img
fallocate -l 10G detailed_evidence.img
What is `fallocate`?
`fallocate` is a CLI command used to allocate disk space to a file without writing disk space to said file. The kernel marks the blocks as allocated in the filesystem's extent tree and the file reports its full size immediately.
On supported filesystems (ext4, xfs, btrfs) […]
`fallocate` is a CLI command used to allocate disk space to a file without writing disk space to said file. The kernel marks the blocks as allocated in the filesystem's extent tree and the file reports its full size immediately.
On supported filesystems (ext4, xfs, btrfs) […]
Original post on hachyderm.io
hachyderm.io
May 30, 2026 at 4:53 PM
What is `fallocate`?
`fallocate` is a CLI command used to allocate disk space to a file without writing disk space to said file. The kernel marks the blocks as allocated in the filesystem's extent tree and the file reports its full size immediately.
On supported filesystems (ext4, xfs, btrfs) […]
`fallocate` is a CLI command used to allocate disk space to a file without writing disk space to said file. The kernel marks the blocks as allocated in the filesystem's extent tree and the file reports its full size immediately.
On supported filesystems (ext4, xfs, btrfs) […]
How to Create a Test File of Any Size in Linux Read more here https://www.tecmint.com/create-exact-size-file-linux-dd-fallocate/
#Linux #opensource #tecmint
#Linux #opensource #tecmint
www.tecmint.com
May 7, 2026 at 6:17 AM
How to Create a Test File of Any Size in Linux Read more here https://www.tecmint.com/create-exact-size-file-linux-dd-fallocate/
#Linux #opensource #tecmint
#Linux #opensource #tecmint
File size is 10M. Total files: 3
Windows users:
copy NUL mock_1.pdf
copy /b NUL mock_1.pdf
Linux users:
fallocate -l 10M mocking_1.pdf
The address of the IN Statehouse is:
200 W. Washington St.
Indianapolis, IN 46204
School: Batesville HS
Fake email gen: temp-mail.org/en/
Good luck!
Windows users:
copy NUL mock_1.pdf
copy /b NUL mock_1.pdf
Linux users:
fallocate -l 10M mocking_1.pdf
The address of the IN Statehouse is:
200 W. Washington St.
Indianapolis, IN 46204
School: Batesville HS
Fake email gen: temp-mail.org/en/
Good luck!
Please everyone make sure to be responsible in using this Indiana Tattale-a-Teacher website to which you can *UPLOAD FILES*
Indiana AG's new "report a teacher" portal is truly something else. Not only can people upload "supporting documentation", but there's a curated collection of those documents for users to browse. It's a state funded website to facilitate targeted hate campaigns.
www.in.gov/attorneygene...
www.in.gov/attorneygene...
February 17, 2024 at 6:10 PM
File size is 10M. Total files: 3
Windows users:
copy NUL mock_1.pdf
copy /b NUL mock_1.pdf
Linux users:
fallocate -l 10M mocking_1.pdf
The address of the IN Statehouse is:
200 W. Washington St.
Indianapolis, IN 46204
School: Batesville HS
Fake email gen: temp-mail.org/en/
Good luck!
Windows users:
copy NUL mock_1.pdf
copy /b NUL mock_1.pdf
Linux users:
fallocate -l 10M mocking_1.pdf
The address of the IN Statehouse is:
200 W. Washington St.
Indianapolis, IN 46204
School: Batesville HS
Fake email gen: temp-mail.org/en/
Good luck!
ebpf でトレースした結果、fallocate した時の方がメタデータ (inode) の更新回数が多いという謎な結果になってる
March 20, 2025 at 10:08 PM
ebpf でトレースした結果、fallocate した時の方がメタデータ (inode) の更新回数が多いという謎な結果になってる
A lot of Linux users still use touch for test files and then wonder why benchmarks look wrong.
touch creates an empty file.
dd creates files with real data.
fallocate creates large files instantly without writing data.
Know which to use and when: www.tecmint.com/create-exact...
touch creates an empty file.
dd creates files with real data.
fallocate creates large files instantly without writing data.
Know which to use and when: www.tecmint.com/create-exact...
How to Create a File of Exact Size in Linux
In this guide, we'll explain how to create files of exact size in Linux using dd and fallocate, when to use each, and how to verify the result.
www.tecmint.com
May 7, 2026 at 4:48 AM
A lot of Linux users still use touch for test files and then wonder why benchmarks look wrong.
touch creates an empty file.
dd creates files with real data.
fallocate creates large files instantly without writing data.
Know which to use and when: www.tecmint.com/create-exact...
touch creates an empty file.
dd creates files with real data.
fallocate creates large files instantly without writing data.
Know which to use and when: www.tecmint.com/create-exact...
Linux 6.17 Will Allow Writing Zeroes More Efficiently To SSDs - https://www.phoronix.com/news/Linux-6.17-fallocate-Write-Zero
Linux 6.17 Will Allow Writing Zeroes More Efficiently To SSDs
In addition to the VFS changes merrged yesterday for allowing multi-device file-systems to better cope with losing a disk, another notable change as part of the VFS pull requests for Linux 6.17 allows more efficiently zeroing out a range on modern NVMe SSDs or SCSI drives...
www.phoronix.com
July 29, 2025 at 9:57 AM
Linux 6.17 Will Allow Writing Zeroes More Efficiently To SSDs - https://www.phoronix.com/news/Linux-6.17-fallocate-Write-Zero
tl;dr, the fallocate to extend your file before you write it standard wisdom is still good advice.
Also TIL that the thread that submits an IO request to io_uring needs to be kept alive until the operation completes, otherwise whatever other thread picks up the work will mark it ECANCELLED.
Also TIL that the thread that submits an IO request to io_uring needs to be kept alive until the operation completes, otherwise whatever other thread picks up the work will mark it ECANCELLED.
April 30, 2025 at 2:42 AM
tl;dr, the fallocate to extend your file before you write it standard wisdom is still good advice.
Also TIL that the thread that submits an IO request to io_uring needs to be kept alive until the operation completes, otherwise whatever other thread picks up the work will mark it ECANCELLED.
Also TIL that the thread that submits an IO request to io_uring needs to be kept alive until the operation completes, otherwise whatever other thread picks up the work will mark it ECANCELLED.
💡 Need a dummy file for testing? Create files instantly with `mkfile`
https://syntax.club/profile/andreruffert.com/snap/3moiggkaiks2e
https://syntax.club/profile/andreruffert.com/snap/3moiggkaiks2e
![Syntax highlighted Bash:
# macOS
# Create a file of the specified size
mkfile [-nv] size[b|k|m|g] filename
# Create a 10 MB file
mkfile 10m 10MB.pdf
# Linux equivalent
# Allocate a 10 MB file on disk
fallocate -l 10M 10MB.pdf](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:sdt6u6ybm3ck5vueftpvnxms/bafkreiedrbflwewwygr6lrk3o6rkb5vazydou64wrjg25hfew4iziyckxm)
June 17, 2026 at 1:48 PM
💡 Need a dummy file for testing? Create files instantly with `mkfile`
https://syntax.club/profile/andreruffert.com/snap/3moiggkaiks2e
https://syntax.club/profile/andreruffert.com/snap/3moiggkaiks2e
いわゆるsparseファイルの作り方。Windowsならfsutilで、Linuxならfallocateで。Windows知らなかったな。
ちょっと便利なダミーファイル作成コマンド（Windows/Ubuntu） | 株式会社ビヨンド
データ転送のトラブルシュート時に数十MBのテストデータが必要になる場面がありました。そんな時に役立つのが「ダミーファイル」です。今回は、このダミーファイルをWindowsとUbuntu環境でコマンドから簡単に作成する方法をご紹介いたします。
beyondjapan.com
April 13, 2025 at 1:43 AM
いわゆるsparseファイルの作り方。Windowsならfsutilで、Linuxならfallocateで。Windows知らなかったな。
SMB subsystem lands wave of security and data-corruption fixes
ksmbd gets hardened against heap leaks and buffer overflows, the CIFS client fixes multiple fallocate data-corruption bugs, and Ste…
#DataCorruption #Fallocate #Ksmbd #Security #SMB
https://kerneldispatch.com/posts/mainline-2026-09-02
ksmbd gets hardened against heap leaks and buffer overflows, the CIFS client fixes multiple fallocate data-corruption bugs, and Ste…
#DataCorruption #Fallocate #Ksmbd #Security #SMB
https://kerneldispatch.com/posts/mainline-2026-09-02
September 2, 2026 at 1:47 PM
SMB subsystem lands wave of security and data-corruption fixes
ksmbd gets hardened against heap leaks and buffer overflows, the CIFS client fixes multiple fallocate data-corruption bugs, and Ste…
#DataCorruption #Fallocate #Ksmbd #Security #SMB
https://kerneldispatch.com/posts/mainline-2026-09-02
ksmbd gets hardened against heap leaks and buffer overflows, the CIFS client fixes multiple fallocate data-corruption bugs, and Ste…
#DataCorruption #Fallocate #Ksmbd #Security #SMB
https://kerneldispatch.com/posts/mainline-2026-09-02
O EXT4 no Linux 7.3 está insano! 📈 De 1,92M para 2,19M IOPS com SSDs PCIe Gen5. Parallel DIO writes, otimizações no fallocate() e muito mais. Artigo completo com todos os detalhes. Saiba mais -> tinyurl.com/mp4z29s6
EXT4 no Linux 7.3: As Melhorias de Performance que Estão Revolucionando o Armazenamento
Blog com notícias sobre, Linux, Android, Segurança , etc
tinyurl.com
August 20, 2026 at 11:49 AM
O EXT4 no Linux 7.3 está insano! 📈 De 1,92M para 2,19M IOPS com SSDs PCIe Gen5. Parallel DIO writes, otimizações no fallocate() e muito mais. Artigo completo com todos os detalhes. Saiba mais -> tinyurl.com/mp4z29s6
[Foundation devlog (2)]
* Remove and Insert calls added.
* host_file Remove is NI; host_file Insert is written but untested.
These use Linux's `fallocate` where possible!
* [!] driver Remove and Insert are NI.
* Preparation for the new Size, Clear, Delete, and Create calls.
* Source code bugfix […]
* Remove and Insert calls added.
* host_file Remove is NI; host_file Insert is written but untested.
These use Linux's `fallocate` where possible!
* [!] driver Remove and Insert are NI.
* Preparation for the new Size, Clear, Delete, and Create calls.
* Source code bugfix […]
Original post on social.golemwire.com
social.golemwire.com
August 19, 2026 at 1:44 AM
[Foundation devlog (2)]
* Remove and Insert calls added.
* host_file Remove is NI; host_file Insert is written but untested.
These use Linux's `fallocate` where possible!
* [!] driver Remove and Insert are NI.
* Preparation for the new Size, Clear, Delete, and Create calls.
* Source code bugfix […]
* Remove and Insert calls added.
* host_file Remove is NI; host_file Insert is written but untested.
These use Linux's `fallocate` where possible!
* [!] driver Remove and Insert are NI.
* Preparation for the new Size, Clear, Delete, and Create calls.
* Source code bugfix […]
🚨 EUVD-2026-55574
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
August 10, 2026 at 2:01 PM
🚨 EUVD-2026-55574
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
🚨 EUVD-2026-55574
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
August 10, 2026 at 2:01 PM
🚨 EUVD-2026-55574
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
📊 n/a
🏢 Linux
📝 In the Linux kernel, the following vulnerability has been resolved:
smb/client: handle overlapping allocated ranges in fallocate
smb3_simple_fallocate_range(...
🔗 https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-55574
#cybersecurity #infosec #cve #euvd
結論、fallocate は事前に行うと I/O 時に inode の更新回数や block allocation の回数を大きく減らし、さらに disk 上で consecutive な allocation を可能とするが、自分の環境 (ext4, DIRECT I/O) では block sequential / random write のレインテシには大きな影響がない。できれば xfs でも試して見たい。
March 25, 2025 at 3:10 PM
結論、fallocate は事前に行うと I/O 時に inode の更新回数や block allocation の回数を大きく減らし、さらに disk 上で consecutive な allocation を可能とするが、自分の環境 (ext4, DIRECT I/O) では block sequential / random write のレインテシには大きな影響がない。できれば xfs でも試して見たい。