fallocate

Wat het doet

Zo schrijf je het

fallocate [-c|-p|-z] [-o OFFSET] -l LENGTH [-n] FILE
fallocate -d [-o OFFSET] [-l LENGTH] FILE
fallocate -x [-o OFFSET] -l LENGTH FILE

Meest gebruikt

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$ als gewone gebruiker# als root (of met sudo)

1. 1Create a 1 GiB file at once

   $fallocate -l 1G /var/tmp/test.img
   $ls -lh /var/tmp/test.img

   Done in milliseconds.

2. 2Fill a disk for a test

   #fallocate -l 9G /data/fill

   Test alerts and app behaviour on a full disk; delete it after.

3. 3Make a sparse file smaller on disk

   $fallocate -d disk.img

   Zero blocks are freed (VM images, backups).

4. 4Free a range in a log file

   $fallocate -p -o 0 -l 100M big.log

   The file keeps its size, uses less disk.

5. 5Reserve space without changing the size

   $fallocate -n -l 500M db.dat

   Space is reserved for later writes.

6. 6Compare used and visible size

   $du -h --apparent-size disk.img; du -h disk.img

   After -d the real use is smaller.

7. 7Swap file (careful)

   #fallocate -l 1G /swapfile

   Works on many file systems, but swapon may refuse it; dd is the safe way.

8. 8Test file for upload limits

   $fallocate -l 101M /tmp/too-big.bin

   Test a 100 MB upload limit of a web app.

9. 9Truncate is different

   $truncate -s 1G sparse.img

   truncate makes a sparse file (no blocks reserved).

10. 10Check quota limits

    $fallocate -l 2G ~/quota-test

    Fails with "Disk quota exceeded" when the limit is lower.

Niets past bij dit filter.

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