Re: nfs bug df: Can I lock up my kernel and overflow this buffer?
On 05/10/05 00:21, Billy Newsom wrote: Jonathan Noack wrote: On 05/09/05 23:14, Billy Newsom wrote: From the fstab(5) man page: The fourth field, (fs_mntops), describes the mount options associated with the file system. It is formatted as a comma separated list of options. It contains at least the type of mount (see fs_type below) plus any additional options appropriate to the file system type. See the options flag (-o) in the mount(8) page and the file system specific page, such as mount_nfs(8), for additional options that may be specified. That is how I read the man page, too, long ago. But when I tried the -o option on the commandline, I was unable to send mount all of the mount_nfs commandline switches I needed. I either misunderstand the mount -o option, or it doesn't work for all of the mount_nfs stuff I tried to send it. In other words, the -o option seems to not like any of the many switches understood by mount_nfs hence I seemed to be forced to use mount_nfs directly. And that precludes using it in fstab. You are not restricted to only the -o option with fstab. The native mount_nfs switches work fine with it. This is stated in the second half of the last sentence I quoted above (note the and). Thus, the same options you use on the command line work with fstab. What trouble did you have with fstab? You can specify as many options as you want as long as you separate them with commas (I think putting a '=' between an option and its value is also necessary, although I don't know for sure). For you it should look like this (assuming you want read/write): dell:/nfs /dellbak nfs rw,-s,-x=2,-T 0 0 I don't know. Since mount wasn't able to understand those switches on the commandline, I never tried anything in fstab, for the sake of not causing any problems with my boot. The handbook page on nfs has a few simple examples toward the bottom (first hit on a Google search for freebsd nfs fstab): http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/network-nfs.html To test the line I gave you just add it to /etc/fstab and see if mount /dellbak works. It'll give you an error message if something is wrong. For example, the options specified work perfectly for me and the mount command completes successfully. Adding a -z to it gives an illegal option error. # grep shared /etc/fstab server:/shared /mnt nfs rw,-s,-x=2,-T 0 0 # mount /mnt # umount /mnt add -z # grep shared /etc/fstab server:/shared /mnt nfs rw,-s,-x=2,-T,-z 0 0 # mount /mnt mount_nfs: illegal option -- z usage: mount_nfs [-23bcdiLlNPsTU] [-a maxreadahead] [-D deadthresh] [-g maxgroups] [-I readdirsize] [-o options] [-R retrycnt] [-r readsize] [-t timeout] [-w writesize] [-x retrans] rhost:path node Anyone tried that sort of stuff in fstab? I'm a little skeptical. I use that sort of stuff and have for a long time. Here's one of my fstab lines: optimator:/usr/home /usr/home nfs rw,-3,-T,-r=32768,-w=32768 0 0 It's obvious you don't believe me but why are you unwilling to try it yourself? -- Jonathan Noack | [EMAIL PROTECTED] | OpenPGP: 0x991D8195 signature.asc Description: OpenPGP digital signature
Re: nfs bug df: Can I lock up my kernel and overflow this buffer?
Jonathan Noack wrote: Anyone tried that sort of stuff in fstab? I'm a little skeptical. I use that sort of stuff and have for a long time. Here's one of my fstab lines: optimator:/usr/home /usr/home nfs rw,-3,-T,-r=32768,-w=32768 0 0 It's obvious you don't believe me but why are you unwilling to try it yourself? Well, because this fails to work on the commandline: #mount -o -s -x 2 -T dell:/nfs /dellbak I tried tons of different ways, never could get mount to do that, so I gave up on fstabbing options. Since the above mount command wouldn't even work, I figured I could forget about putting those same options (which mount calls illegal) in the fstab file. That's where the man pages only go so far. Without the examples you give, I was pretty sure that it was pointless to get fstab options to do what mount wouldn't. What it boils down to is that mount is fine with these options in fstab, but barfs when doing them on the commandline. That was so couter-intuitive, I went around it for the sake of getting things done. FreeBSD man pages are nice and all, but without a textbook siting by with some examples, it can be difficult. I learned Unix pretty much ad hoc, so I find that examples (such as you gave) are worth much more than man pages now that I know most of the basics. Thanks. But what I did discover is that if I mount the same nfs resource multiple times, I get multiple, identical mounts (using fstab options, or commandline, either one). I have to umount each one serially. How is this a feature? What good does it do me if I mount the same nfs drive to the same place n times? Won't that eventually cause a deadlock as n increases beyond a few hundred or thousand? -- especially when the NFS server goes down? Shouldn't the second and subsequent mounts either fail or not be attempted due to a sanity check? #mount /usr mount: /dev/ad0s1f: Device busy Exit 1 That seems reasonable for /usr. But as I stated before, NFS resources nevere apparently become busy, and there is no sanity check to prevent mulitiple simultaneous mounts of identical file systems on identical file trees. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: nfs bug df: Can I lock up my kernel and overflow this buffer?
On Tue, May 10, 2005 at 05:16:16PM -0500, Billy Newsom wrote: Jonathan Noack wrote: Anyone tried that sort of stuff in fstab? I'm a little skeptical. I use that sort of stuff and have for a long time. Here's one of my fstab lines: optimator:/usr/home /usr/home nfs rw,-3,-T,-r=32768,-w=32768 0 0 It's obvious you don't believe me but why are you unwilling to try it yourself? Well, because this fails to work on the commandline: #mount -o -s -x 2 -T dell:/nfs /dellbak I tried tons of different ways, never could get mount to do that, so I gave up on fstabbing options. Note that mount(8) (as well as mount_nfs(8)) says about the -o flag that Options are specified with a -o flag followed by a comma separated string of options. If you try writing it as the manpage says, i.e. like mount -o -s,-x=2,-T dell:/nfs /dellbak it should work fine. Since the above mount command wouldn't even work, I figured I could forget about putting those same options (which mount calls illegal) in the fstab file. That's where the man pages only go so far. Without the examples you give, I was pretty sure that it was pointless to get fstab options to do what mount wouldn't. What it boils down to is that mount is fine with these options in fstab, but barfs when doing them on the commandline. That was so couter-intuitive, I went around it for the sake of getting things done. It works fine on the commandline, you just got the syntax for the commandline wrong. FreeBSD man pages are nice and all, but without a textbook siting by with some examples, it can be difficult. I learned Unix pretty much ad hoc, so I find that examples (such as you gave) are worth much more than man pages now that I know most of the basics. Man pages often have some examples, but learning things only from manpages can indeed be a bit difficult. Thanks. But what I did discover is that if I mount the same nfs resource multiple times, I get multiple, identical mounts (using fstab options, or commandline, either one). I have to umount each one serially. How is this a feature? It is a feature in that the system does exactly what you asked it to do. This is usually less painful than systems that try to guess what you actually meant. What good does it do me if I mount the same nfs drive to the same place n times? None that I can think of, which doesn't mean that there is no use for it. Won't that eventually cause a deadlock as n increases beyond a few hundred or thousand? -- especially when the NFS server goes down? Probably not a deadlock, but possible a resource starvation - so don't do that. Shouldn't the second and subsequent mounts either fail or not be attempted due to a sanity check? #mount /usr mount: /dev/ad0s1f: Device busy Exit 1 That seems reasonable for /usr. But as I stated before, NFS resources nevere apparently become busy, and there is no sanity check to prevent mulitiple simultaneous mounts of identical file systems on identical file trees. -- Insert your favourite quote here. Erik Trulsson [EMAIL PROTECTED] ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: nfs bug df: Can I lock up my kernel and overflow this buffer?
Erik Trulsson wrote: Note that mount(8) (as well as mount_nfs(8)) says about the -o flag that Options are specified with a -o flag followed by a comma separated string of options. If you try writing it as the manpage says, i.e. like mount -o -s,-x=2,-T dell:/nfs /dellbak it should work fine. I felt pretty confident I had tried something of this sort, and of course now that you say all of that, it works for me. I probably didn't use the hyphens, nor the equals sign, etc. It works fine on the commandline, you just got the syntax for the commandline wrong. But what I did discover is that if I mount the same nfs resource multiple times, I get multiple, identical mounts (using fstab options, or commandline, either one). I have to umount each one serially. How is this a feature? It is a feature in that the system does exactly what you asked it to do. This is usually less painful than systems that try to guess what you actually meant. What good does it do me if I mount the same nfs drive to the same place n times? None that I can think of, which doesn't mean that there is no use for it. Won't that eventually cause a deadlock as n increases beyond a few hundred or thousand? -- especially when the NFS server goes down? Probably not a deadlock, but possible a resource starvation - so don't do that. Which leads me to a test. I am going to try and take a server down this way and see what resources I can max out or overflow by mounting and re-mounting the same thing over and over. I'll write a shell script with an infinite loop, and run it on an old server of mine. Then maybe I'll pull its LAN cable (virtually and actually) and see what happens. Perhaps I'll cross-post the results to the hackers list if I get some interesting results. BN ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
nfs bug df: Can I lock up my kernel and overflow this buffer?
Here's something pretty stupid about either the code in mount, df, or both. I'm on the verge of a denial of service if this lasts much longer. When I mount an nfs device more than once, I get this ridiculous output from df and mount: #df Filesystem 1K-blocksUsed Avail Capacity Mounted on /dev/ad0s1a253678 137554 9583059%/ devfs 1 1 0 100%/dev /dev/ad0s1e253678 18 233366 0%/tmp /dev/ad0s1f 7782878 3273986 388626246%/usr /dev/ad0s1d253678 125386 10799854%/var devfs 1 1 0 100%/var/named/dev dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak #mount /dev/ad0s1a on / (ufs, NFS exported, local) devfs on /dev (devfs, local) /dev/ad0s1e on /tmp (ufs, local, soft-updates) /dev/ad0s1f on /usr (ufs, NFS exported, local, soft-updates) /dev/ad0s1d on /var (ufs, NFS exported, local) devfs on /var/named/dev (devfs, local) dell:/nfs on /dellbak (nfs) dell:/nfs on /dellbak (nfs) dell:/nfs on /dellbak (nfs) dell:/nfs on /dellbak (nfs) dell:/nfs on /dellbak (nfs) dell:/nfs on /dellbak (nfs) Ha, ha! How many times will this last line repeat itself? I'm curious to see if I can get it to give me a screenful of data. Will this eventually crash the kernel or fill some buffer up? All I'm doing is mounting the same nfs drive over and over. Normally, mounting a device twice will just give a device busy or something. Is there some sanity check missing that will prevent mount_nfs from actually mounting the same resource at the same mount point over and over? Details: * FreeBSD 5.3. Updated and compiled in mid-February. I froze it there and may soon upgrade to 5.4, but I don't count on this fixing this issue. * I needed to make sure I had an nfs drive mounted properly, even after a reboot, but didn't want to (couldn't?) put it in fstab. So cron has this particular line(s). 44 10 * * * /sbin/mount_nfs -s -x 2 -T dell:/nfs /dellbak * I am connecting to a local net NFS server running Windows 2000 and Services for UNIX 3.5. Due to some major problems with rebooting and NFS, I determined that I needed some of the special commands (-s -x 2) to enable the server to reboot. * I put the mount_nfs command in cron and in an rc.d startup script because I didn't see a way to put all of the options in fstab, nor did I particularly enjoy booting the FreeBSD server without connecting to the NFS drive I would fill up my root directory pretty fast. * Look at the fsid for /dellbak below, using verbose output. Pretty odd. # mount -v /dev/ad0s1a on / (ufs, NFS exported, local, writes: sync 165 async 29170, reads: sync 2308 async 45, fsid f044aa41725bf386) devfs on /dev (devfs, local, fsid 01ff00040400) /dev/ad0s1e on /tmp (ufs, local, soft-updates, writes: sync 9 async 4002, reads: sync 125 async 0, fsid f144aa411e8f31da) /dev/ad0s1f on /usr (ufs, NFS exported, local, soft-updates, writes: sync 420 async 129755, reads: sync 170752 async 1401, fsid f144aa4134661c3c) /dev/ad0s1d on /var (ufs, NFS exported, local, writes: sync 32187 async 49433, reads: sync 4043 async 102, fsid f244aa416aeef171) devfs on /var/named/dev (devfs, local, fsid 02ff00040400) dell:/nfs on /dellbak (nfs, fsid 03ff00020200) dell:/nfs on /dellbak (nfs, fsid 04ff00020200) dell:/nfs on /dellbak (nfs, fsid 05ff00020200) dell:/nfs on /dellbak (nfs, fsid 06ff00020200) dell:/nfs on /dellbak (nfs, fsid 07ff00020200) dell:/nfs on /dellbak (nfs, fsid 08ff00020200) Any help? Thanks. BN ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: nfs bug df: Can I lock up my kernel and overflow this buffer?
On Mon, May 09, 2005 at 11:14:51PM -0500, Billy Newsom wrote: Here's something pretty stupid about either the code in mount, df, or both. I'm on the verge of a denial of service if this lasts much longer. Why do you think so? When I mount an nfs device more than once, I get this ridiculous output from df and mount: #df Filesystem 1K-blocksUsed Avail Capacity Mounted on /dev/ad0s1a253678 137554 9583059%/ devfs 1 1 0 100%/dev /dev/ad0s1e253678 18 233366 0%/tmp /dev/ad0s1f 7782878 3273986 388626246%/usr /dev/ad0s1d253678 125386 10799854%/var devfs 1 1 0 100%/var/named/dev dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak dell:/nfs 8883912 4104516 477939646%/dellbak Why's it ridiculous? You mounted it more than once, so it appears more than once in the list of mounted filesystems. * Look at the fsid for /dellbak below, using verbose output. Pretty odd. Why is it odd? The fsid is by definition different for different mounts. Kris pgpoQVP1xyMlu.pgp Description: PGP signature
Re: nfs bug df: Can I lock up my kernel and overflow this buffer?
On 05/09/05 23:14, Billy Newsom wrote: snip Details: * FreeBSD 5.3. Updated and compiled in mid-February. I froze it there and may soon upgrade to 5.4, but I don't count on this fixing this issue. * I needed to make sure I had an nfs drive mounted properly, even after a reboot, but didn't want to (couldn't?) put it in fstab. So cron has this particular line(s). 44 10 * * * /sbin/mount_nfs -s -x 2 -T dell:/nfs /dellbak From the fstab(5) man page: The fourth field, (fs_mntops), describes the mount options associated with the file system. It is formatted as a comma separated list of options. It contains at least the type of mount (see fs_type below) plus any additional options appropriate to the file system type. See the options flag (-o) in the mount(8) page and the file system specific page, such as mount_nfs(8), for additional options that may be specified. What trouble did you have with fstab? You can specify as many options as you want as long as you separate them with commas (I think putting a '=' between an option and its value is also necessary, although I don't know for sure). For you it should look like this (assuming you want read/write): dell:/nfs /dellbak nfs rw,-s,-x=2,-T 0 0 -- Jonathan Noack | [EMAIL PROTECTED] | OpenPGP: 0x991D8195 signature.asc Description: OpenPGP digital signature
Re: nfs bug df: Can I lock up my kernel and overflow this buffer?
Jonathan Noack wrote: On 05/09/05 23:14, Billy Newsom wrote: From the fstab(5) man page: The fourth field, (fs_mntops), describes the mount options associated with the file system. It is formatted as a comma separated list of options. It contains at least the type of mount (see fs_type below) plus any additional options appropriate to the file system type. See the options flag (-o) in the mount(8) page and the file system specific page, such as mount_nfs(8), for additional options that may be specified. That is how I read the man page, too, long ago. But when I tried the -o option on the commandline, I was unable to send mount all of the mount_nfs commandline switches I needed. I either misunderstand the mount -o option, or it doesn't work for all of the mount_nfs stuff I tried to send it. In other words, the -o option seems to not like any of the many switches understood by mount_nfs hence I seemed to be forced to use mount_nfs directly. And that precludes using it in fstab. What trouble did you have with fstab? You can specify as many options as you want as long as you separate them with commas (I think putting a '=' between an option and its value is also necessary, although I don't know for sure). For you it should look like this (assuming you want read/write): dell:/nfs /dellbak nfs rw,-s,-x=2,-T 0 0 I don't know. Since mount wasn't able to understand those switches on the commandline, I never tried anything in fstab, for the sake of not causing any problems with my boot. Anyone tried that sort of stuff in fstab? I'm a little skeptical. Thanks. BN ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
