Date: Mon, 20 Nov 2017 14:02:47 -0600 From: Karl Denninger <karl@denninger.net> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: MSDOS Filesystem question related to "read-only" files Message-ID: <e6a682a1-322e-a677-3d5e-0a7a503ebd40@denninger.net> In-Reply-To: <CAG6CVpUZumZaU9xVcri1Ry8=C6j6JrjX5F6qd3oKatYZXFu6Kg@mail.gmail.com> References: <f4ccb904-63fd-4641-89c8-09357fbb5a1c@denninger.net> <CAG6CVpUZumZaU9xVcri1Ry8=C6j6JrjX5F6qd3oKatYZXFu6Kg@mail.gmail.com>
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This is a cryptographically signed message in MIME format. --------------ms020103050803010300020803 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable root@Test-MCP:/home/karl/HD-MCP # cd /mnt root@Test-MCP:/mnt # mount /dev/ufs/rootfs on / (ufs, local, noatime, soft-updates, nfsv4acls) devfs on /dev (devfs, local) tmpfs on /tmp (tmpfs, local) /dev/da0s1 on /mnt (msdosfs, local) root@Test-MCP:/mnt # ls -al total 408 drwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0=C2=A0=C2=A0 4096 Jan=C2=A0= 1=C2=A0 1980 . drwxr-xr-x=C2=A0 20 root=C2=A0=C2=A0 wheel=C2=A0=C2=A0=C2=A0=C2=A0 512 No= v 20 16:04 .. drwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0=C2=A0=C2=A0 4096 Nov 19 = 11:20 System Volume Information -rwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0 127979 Nov 19 22:54 cam2-2017-11-19-22-54-47.jpg -rwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0 271295 Nov 19 22:57 cam2-2017-11-19-22-57-20.jpg root@Test-MCP:/mnt # chmod u-w * root@Test-MCP:/mnt # ls -al total 408 drwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0=C2=A0=C2=A0 4096 Jan=C2=A0= 1=C2=A0 1980 . drwxr-xr-x=C2=A0 20 root=C2=A0=C2=A0 wheel=C2=A0=C2=A0=C2=A0=C2=A0 512 No= v 20 16:04 .. drwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0=C2=A0=C2=A0 4096 Nov 19 = 11:20 System Volume Information -rwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0 127979 Nov 19 22:54 cam2-2017-11-19-22-54-47.jpg -rwxr-xr-x=C2=A0=C2=A0 1 hdmcp=C2=A0 wheel=C2=A0 271295 Nov 19 22:57 cam2-2017-11-19-22-57-20.jpg root@Test-MCP:/mnt # Nope.=C2=A0 The "w" is still there. No error returned from the "chmod" command (or if I call it from a C program) but the file mode is NOT changed whether I'm doing it as the superuser or as the owner of the file (and directory) On 11/20/2017 12:30, Conrad Meyer wrote: > Hi Karl, > > In fact, msdosfs in FreeBSD should set the FAT READONLY attribute > under two conditions: > > 1. The owner chmod's the file non-writeable (chmod u-w) (what you've > described, I think). Or, > 2. The super user or otherwise privileged user sets the "readonly" > flag on the file via chflags(1). > > How have you determined that chmod u-w does nothing? What version of > FreeBSD are you using? > > Best, > Conrad > > > On Mon, Nov 20, 2017 at 7:36 AM, Karl Denninger <karl@denninger.net> wr= ote: >> I'm running into an interesting issue here and wondering if there's a >> way to do this under FreeBSD. >> >> MSDOS filesystems have a "primitive" permission capability; >> specifically, they can have a "Read-only" attribute on a file. It loo= ks >> like OpenBSD supports this from reading their man pages. >> >> FreeBSD doesn't appear to. When you mount a msdos filesystem (e.g. a >> USB stick) whoever owns the parent directory where you mount it gives >> you the permissions and "ownership" of files on said filesystem. All >> good so far. But attempting to chmod a file to remove write permissio= n >> "succeeds" (returns success) but does nothing. >> >> Is this capability simply not present on FreeBSD? I'm interested in >> using it as a means of "flagging" files on a USB stick in an applicati= on >> that I do not want to remove if the stick fills (basically, to "protec= t" >> them from being aged off) and it appears there's no way to do it, othe= r >> than to use something unique in the filename that I would then have to= >> pay attention to. >> >> -- >> Karl Denninger >> karl@denninger.net <mailto:karl@denninger.net> >> /The Market Ticker/ >> /[S/MIME encrypted email preferred]/ --=20 Karl Denninger karl@denninger.net <mailto:karl@denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ --------------ms020103050803010300020803 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC DdgwggagMIIEiKADAgECAhMA5EiKghDOXrvfxYxjITXYDdhIMA0GCSqGSIb3DQEBCwUAMIGL 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