1

I just sent a local mail using the following syntax:

echo "Testing" | mail -s "This is just a test" root@localhost

Then I log into root using:

sudo -i

And check my mail. The message is there. If I repeat the mail command and log into root using:

su root

The mail is not in my mailbox. In both cases I am logging into the root account, so what is happening here? It's a fairly new, basic installation of CentOS 7.

I even checked again by logging in using su and when it wasn't there I logged out and back in using sudo -i and sure enough, the mail was there.

  • What happens with su - root? (Note the - argument) – Andrew Henle Apr 25 '17 at 22:26
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The cause of this behavior is the MAIL environment variable. When you switch to root with

sudo -i

you simulate an intial login (-i) and the MAIL environment variable is set to /var/spool/mail/root. When you switch to root with

su root

The MAILenvironment variable stay to its old value i.e. /var/spool/mail/jo and the command mail check the mailbox of the user and not the mailbox of root. This why you see it empty.

  • Brilliant answer. You got it spot on. I tried logging into root with sudo -i, then echo $MAIL gives /var/spool/mail/root. Then I try the other way with su root and I get /var/spool/mail/user. Perfect answer. Thanks. – bitofagoob Apr 25 '17 at 21:53

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