SUMMARY: mount problems

From: Moshe Linzer (
Date: Wed Nov 30 1994 - 21:04:24 CST

Here is the original question:

We are experiencing problems with our automounted directories, which I
think come from having too many mounts. Most of our machines have
around 210 mounts defined (don't ask!), and when the automount gets
going, this number usually rises above 256. I noticed that in
/etc/mtab, the mounter uses device numbers (dev=) from 8200 to 82ff,
and starts to reuse device number 82ff when it reaches the end. When
this happens, after "cd" to a newly automounted directory, we receive a
wrong path from the pwd command, and "could not find mount point" from
a "df .". Does this indicate a limit of 255 mounts on a single
machine? I could find no reference to this issue in any doc, and no
explanation of the dev= parm in mtab. We are running a mix of SunOS
4.1.1, 4.1.2, and 4.1.3. Has anybody come across this phenomenon

I received one relevant answer, which was subsequently confirmed by SUN.
Many thanks to Nate Itkin for the following:

From: Nate Itkin <>

I don't think the nfs implementation in SunOS 4.1.x will allocate more than
one major device for nfs file systems. Thus, you get a maximum of 256 nfs
mounts - one per minor device number (0x0 to 0xff).

>From Sun rep:

> The dev= entry is the device number of the fs.
> --------------------FROM SUNSOLVE------------------------
> That's the "dev=" string you see. This is for the
> benefit of getwd() et al. The hex number represents the device number
> for the filesystem. This is a dev_t i.e. a short (16 bits). The
> first 8 bits are reserved for the device major number and the second
> 8 bits are for the minor number.
> ---------------------------------------------------------
> As you have found there is a fixed limit of 256 NFS mounts
> available. I'm afraid the only workaround to this is to use
> the automounter (with indirect maps) to reduce the number of
> concurrent NFS mounts.

Well, I guess that's it - watch your number of mounts!

Many thanks to all,


Moshe Linzer Phone: (972) 9-594-247
Unix Systems Manager Fax: (972) 9-558-322
National Semiconductor, Israel E-mail:

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