Date: Sat, 6 Mar 1999 15:16:53 -0800 (PST) From: dhesi@rahul.net To: FreeBSD-gnats-submit@freebsd.org Subject: bin/10444: enhancement: avoid lost mail when mail filesystem is not mounted Message-ID: <199903062316.PAA13210@blue.rahul.net>
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>Number: 10444
>Category: bin
>Synopsis: avoiding lost mail when mail filesystem is not mounted
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Sat Mar 6 15:20:01 PST 1999
>Closed-Date:
>Last-Modified:
>Originator: Rahul Dhesi
>Release: FreeBSD 2.2.8-19990120-SNAP i386
>Organization:
a2i network
>Environment:
not relevant, aplies to all versions of all UNIXes
>Description:
Consider the situation when for some reason the filesystem
that holds incoming mailboxes is not mounted. This can
happen (a) in the case of a disk problem or (b) if the
filesystem comes from a remote NFS server and that server
was down when our machine rebooted. But suppose the normal
mount point of the filesystem is an empty directory with
the same pathname as the intended pathname of the mail
filesystem. E.g., let /var/mail exist but let it be the
mount point where the filesystem will actually be mounted.
Mail delivery programs are not normally prepared to deal
with this situation. Incoming mail arrives for a user u
and gets delivered into /var/mail/u . When the filesystem
finally gets mounted over /var/mail, the file /var/mail/u
is now invisible, and user u has effectively lost the
incoming message. He won't see it until the next time that
the mail filesystem remains unmounted.
I have classified this PR as 'non-critical', but in fact
in certain environments this problem can be very serious.
The silent loss of incoming mail is always a serious problem.
>How-To-Repeat:
1. Arrange to have the filesystem that will hold incoming mail
be not mounted, but let /var/mail be an empty directory.
2. Send mail to any local user.
3. Mount the /var/mail filesystem.
4. Ask the user to look for his incoming mail.
>Fix:
I have been the following solution for many years. The
local mailer looks for a file called '.MAIL.FSYS' in the
mail filesystem. If it exists, mail delivery occurs as
usual. If it does not exist, the mailer exits with a
temporary failure, and mail remains queued.
I propose that FreeBSD adopt this convention, and that by
default mail.local check for the existence of '.MAIL.FSYS'
as above. Also all FreeBSD ports for all programs that do
mail delivery, such as procmail, should do the same check.
And this convention should be documented, thus encouraging
all all authors of mail programs that do mail delivery to
incoporate this check into their software.
The C code given below may be inserted almost anywhere,
the only variable part being the directory path.
{
struct stat statbuf;
#define MARKER "/var/mail/.MAIL.FSYS"
if (stat(MARKER, &statbuf) != 0) {
/* not mounted, exit with temp error */
exit(75);
}
}
>Release-Note:
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