Member Avatar for linux

Recently I downloaded the Ubuntu ISO (desktop version). It said something like 680MB file, but when it finished downloading, it was 715MB... I have two questions:

1. Why are they expanding?

2. How can I fit this ISO on a CD if my cd can only fit 700MB?

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  • Latest Post Latest Post by jbennet

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Three simple causes explain why an ISO can look one size while the finished file looks a bit larger: unit/notation differences, filesystem/sector padding, and reporting quirks from the server or downloader. Building on , filesystem allocation can affect "size on disk" values; that is part of the picture. was pointing at the decimal vs binary issue — the correct distinction is between 10^3 (decimal) and 2^10 (binary) prefixes, which is the usual source of the apparent mismatch (binary prefixes).

Check the exact byte count first. On Windows use Properties; on Linux a quick check is stat -c %s filename.iso or ls -l --block-size=1 filename.iso to see the raw byte count. Convert those bytes to the unit the download page uses (decimal MB vs mebibyte) before assuming anything is wrong. If the server advertises one unit and your OS shows another, the numbers will not match even though the file is fine.

ISOs are also padded to CD sector sizes and can include boot records or filesystem extensions, which adds a few kilobytes or megabytes. See the ISO image notes for why images have sector alignment (ISO image). When burning, always use your burner’s "Burn image" / "Write image" option — not "copy file onto disc" — so the ISO is written sector-for-sector. Ubuntu’s burning documentation covers safe steps and common pitfalls (Burning ISOs on Ubuntu).

Quick checklist: 1) verify the raw byte size; 2) compare checksums (use md5sum or sha256sum) against the publisher’s sums; 3) burn the image with a proper "write image" tool; 4) if it truly exceeds the disc capacity, use a DVD or USB installer. This will resolve almost all cases where the downloaded ISO appears "bigger" than expected.

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Member Avatar for TheNNS

ok, a cd actually has little more than 700MB. this also was my concern, but when i clicked on the cd properties, it had a total of something like 734MB. so don't worry about that part, it'll fit on a single cd.
to answer your first question, i think they are adding more packages to their distro, thus making it a little bigger. so go ahead and burn the iso on a cd and enjoy the wonderful world of ubuntu(my favorite distro)

Member Avatar for linux

but when i click download, in the little IE download box, it says 686MB...

Member Avatar for John A

but when i click download, in the little IE download box, it says 686MB...

Doesn't matter... the server was probably acting up.

Member Avatar for mmonaco27

I think it has to do with the size of the blocks the server's hard drive uses compared to your hard drive.

For example if one file is 800 bytes and the server stores data in blocks of 8 bytes then it will take up 100 blocks and exactly 800 bytes. But if you download that file and your computer is storing in groups of 7 you will need to use 115 blocks and use up 805 bytes.

These are all unlikely numbers but should demonstrate the point.

Member Avatar for jbennet

also some people say 1gb = 1000mb and others say its 1024mb (which is correct as there are 8 bits in a byte, not 10)

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