Your message dated Thu, 31 Oct 2013 13:42:12 -0400 with message-id <[email protected]> and subject line mount says loop device is writable, but it isn't. has caused the Debian Bug report #398498, regarding mount says loop device is writable, but it isn't. to be marked as done.
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--- Begin Message ---Package: mount Version: 2.12r-15 Severity: normal This looks like one of those bugs that are so old and people are so accustomed to that they've ceased to think of it as bug, it just seems normal to them. I didn't find a report on it in the BTS, and it seems there should be one... 1) As root, I want to modify an .ISO for a BIOS bootCD. Assuming that's possible. % losetup -f /tmp/di/I4000A23.iso ; echo $? 0 2) So I mount it as 'write': % mount -w -o loop /tmp/di/I4000A23.iso /mnt/tmp ; echo $? 0 3) Did it get mounted as writeble? % mount | grep /tmp /tmp/di/I4000A23.iso on /mnt/tmp type iso9660 (rw,loop=/dev/loop1) "rw" means "read/write", so it looks good. 4) Copy a file over: % cp /tmp/BIOS/I4100A06.EXE /mnt/tmp ; echo $? cp: cannot create regular file `/mnt/tmp/I4100A06.EXE': Read-only file system 1 Questions: Why does step '3)' show "rw" if it's not? Why does return '2)' no error if the '-w' switch failed? Then I looked on Usenet, (where over the years many people have been bitten by this bug), and found a pertinant message: From: Bohdan Linda <[email protected]> Newsgroups: linux.debian.user Subject: Re: Mounting iso images read-write (rw) Date: Mon, 15 Sep 2003 17:20:21 +0200 ISO 9660 is only read-only mountable. You can mount it as read-write, but there is no mechanizm for writes into ISO, so everything ends up as writing to ro. You will have to use mkisofs. http://groups.google.com/group/linux.debian.user/msg/44bcd7810b24d38f?dmode=source&hl=en Maybe B. Linda is correct, as well as practical, but my questions still apply. Why NOT return an error if there's no "mechanizm for writes into ISO"? I'm guessing there's some sort of bureaucratic gridlock, where whoever wrote 'mount' would blame whoever wrote the ISO9660 file system drivers who are themselves blaming it on somebody else. Suggested easy kludges, nothing low-level: Parse for '-w' and an ISO9660 mount, and return an error. Don't show ISO9660 as 'rw'. Hope this helps... -- System Information: Debian Release: 4.0 APT prefers unstable APT policy: (500, 'unstable'), (1, 'experimental') Architecture: i386 (i686) Shell: /bin/sh linked to /bin/dash Kernel: Linux 2.6.16-2-686 Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968) (ignored: LC_ALL set to C) Versions of packages mount depends on: ii libblkid 1.39+1.40-WIP-2006.10.02+dfsg-2 block device id library ii libc6 2.3.6.ds1-8 GNU C Library: Shared libraries ii libuuid1 1.39+1.40-WIP-2006.10.02+dfsg-2 universally unique id library mount recommends no packages. -- no debconf information
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--- Begin Message --------BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 It works this way because people would get annoyed if mount threw an error because they forgot to explicitly specify ro. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJScpZ0AAoJEJrBOlT6nu75RcAIAJY6ED75B3+qRO5MvRL5CT6I M+3r9/ZpD53miPw355KtNxwolqfSZC/8tf4X5NidOb5uC7OyI3IBnuTB5IMLKgdJ xu5qtAkmX3gdPXJ6bM/7/5EqoDkkn3bRSfmKxPGCG6dCaZprUEgQp1ffNv+idR8B wpsJI3yuVGDIInI9MBRSlGh97Hbeyc0aWDbQiAOePVxWNuphG3h+AkhPomWn+bMH u8LK5sRSTkizMNZjEBMEuANTe8ZHTypKlH3Jv/KMto7BXBd/azpCginrEtr3xpi6 J9cTA+8hZKcTS8S8M+rQDcJWN8tKcDZwqZm0TzqavPUIiPUxCgVwKVXiW5cfa7Y= =+I0b -----END PGP SIGNATURE-----
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