From owner-freebsd-fs@freebsd.org Mon Nov 20 20:22:18 2017 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 795E6DF48BB for ; Mon, 20 Nov 2017 20:22:18 +0000 (UTC) (envelope-from karl@denninger.net) Received: from colo1.denninger.net (colo1.denninger.net [67.205.158.196]) by mx1.freebsd.org (Postfix) with ESMTP id 5001E6B97F for ; Mon, 20 Nov 2017 20:22:17 +0000 (UTC) (envelope-from karl@denninger.net) Received: from denninger.net (ip68-1-57-197.pn.at.cox.net [68.1.57.197]) by colo1.denninger.net (Postfix) with ESMTP id E0A1B27461 for ; Mon, 20 Nov 2017 15:22:17 -0500 (EST) Received: from [192.168.10.23] (D13.Denninger.Net [192.168.10.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by denninger.net (Postfix) with ESMTPSA id 2C79C3A1C5F for ; Mon, 20 Nov 2017 14:22:15 -0600 (CST) Subject: Re: MSDOS Filesystem question related to "read-only" files To: freebsd-fs@freebsd.org References: <0e31a0cf-8a97-1d63-8ebb-9c61d22539cb@denninger.net> From: Karl Denninger Message-ID: <501b5bca-a4b0-7bd9-c1bd-09de0394e136@denninger.net> Date: Mon, 20 Nov 2017 14:22:15 -0600 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <0e31a0cf-8a97-1d63-8ebb-9c61d22539cb@denninger.net> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms070700060304010605090001" X-Content-Filtered-By: Mailman/MimeDel 2.1.25 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 20 Nov 2017 20:22:18 -0000 This is a cryptographically signed message in MIME format. --------------ms070700060304010605090001 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Oh, here's another interesting anomaly -- MSDOS filesystems return "0" for the free file count! (gdb) print fsbuf $3 =3D {f_version =3D 537068824, f_type =3D 50, f_flags =3D 4096, f_bsize= =3D 4096, =C2=A0 f_iosize =3D 4096, f_blocks =3D 1949442, f_bfree =3D 1949436, f_ba= vail =3D 1949436, =C2=A0 f_files =3D 0, f_ffree =3D 0, f_syncwrites =3D 3, f_asyncwrites =3D= 5, =C2=A0 f_syncreads =3D 1907, f_asyncreads =3D 0, f_spare =3D 0xbf3fd628, = f_namemax =3D 255, =C2=A0 f_owner =3D 0, f_fsid =3D {val =3D 0xbf3fd680}, f_charspare =3D 0x= bf3fd688 "", =C2=A0 f_fstypename =3D 0xbf3fd6d8 "msdosfs", =C2=A0 f_mntfromname =3D 0xbf3fd6e8 "/dev/da0s1", f_mntonname =3D 0xbf3fd= 740 "/mnt"} Needless to say that can cause some interesting issues if you're coding to avoid potential inode exhaustion and the target is a MSDOS filesystem..... FAT filesystems DO have a maximum file count, incidentall= y. On 11/20/2017 14:08, Karl Denninger wrote: > Oh, my apologies -- I didn't include the version: > > FreeBSD 11.0-STABLE #0 r313159M: Fri Feb=C2=A0 3 09:58:35 CST 2017 > > On an RPI2, but I doubt that matters. > > > On 11/20/2017 14:02, Karl Denninger wrote: >> 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= Nov 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= Nov 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 = wrote: >>>> 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 l= ooks >>>> 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 give= s >>>> you the permissions and "ownership" of files on said filesystem. Al= l >>>> good so far. But attempting to chmod a file to remove write permiss= ion >>>> "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 applica= tion >>>> that I do not want to remove if the stick fills (basically, to "prot= ect" >>>> them from being aged off) and it appears there's no way to do it, ot= her >>>> than to use something unique in the filename that I would then have = to >>>> pay attention to. >>>> >>>> -- >>>> Karl Denninger >>>> karl@denninger.net >>>> /The Market Ticker/ >>>> /[S/MIME encrypted email preferred]/ --=20 Karl Denninger karl@denninger.net /The Market Ticker/ /[S/MIME encrypted email preferred]/ --------------ms070700060304010605090001 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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