server Archives - Beshoy Girgis

My First Bash-Completion Script

Beshoy Girgis — Tue, 20 Nov 2012 01:27:45 +0000

By golly, I’ve finally done it! I love bash completion and must have it on any shell-based device I own. I’ve written countless numbers of scripts but for the most part, they’re fairly self-contained — with the exception of the “perms” script. This script is nice and quick on a one-site box where I can just run “perms” and my permissions for a set get reset to “production”. I use this so that when doing WordPress updates for example, I can chmod -R 777 then run perms after all my updates — nice and quick!

Servers running multiple sites require a more complex perms script which accepts a $1 variable of the domain. From there, I run the specific chowns and chmods and what not for that particular site using a case as well as some defaults that affect all the sites.

I’ve found it annoying to have to type “perms beshoy.girgis.us” or “perms odslabs.com” so I made a quick script to take care of the domain part for me. This script gets dropped in /etc/bash_completion.d/perms

# bash completion for perms

_perms()
{
	  cur=${COMP_WORDS[COMP_CWORD]}
	  COMPREPLY=( $( compgen -W "$(ls /vhosts/)" -- $cur ) )
}
complete -o default -o nospace -F _perms perms

Linux: SSH Strong Public/Private Key Using ssh-keygen

Beshoy Girgis — Fri, 28 Sep 2012 02:09:22 +0000

I’ve come to love encryption. My Linux boxes all do not allow password-authentication for SSL and instead use public authentication. I don’t use a standard 1024 or 2048 bit key, I use… a… 16384 bit key.. yeah.. that crazy dude’s the highest ssh-keygen will allow :). If you decide to be as crazy as I am, be sure to give your computer at least 10 solid minutes to generate the private/public pair. Having to do this on micro Amazon instances takes a while and I find that my ssh session times out before it finishes or I walk away and don’t get back until my session gets timed out.. or…. I forget it’s running and put my computer to sleep. The solution I’ve come up with is to just tell Linux to do it all in the background. I can run the following command as the user needing the key and exit the session immediately after:

ssh-keygen -t rsa -b 16384 -N "" -f ~/.ssh/id_rsa &

Sendmail Failing to Send to Local Domain

Beshoy Girgis — Wed, 19 Sep 2012 21:14:34 +0000

I’ve run into this issue a couple of times now so I’m assuming others are as well. Servers set up on Amazon EC2 with default sendmail configuration seem to get the following error in their /var/log/maillog:

12 Sep 19 19:48:26 DOMAIN sendmail[31192]: q8JJmQQV031192: ... User unknown
13 Sep 19 19:48:26 DOMAIN sendmail[31191]: q8JJmQ0D031191: to=orders@DOMAIN.com, ctladdr=DOMAIN.com (504/502), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30695, relay=[127.0.0.1] [127.0.0.1], dsn=5.1.1, stat=User unknow
14 Sep 19 19:48:26 DOMAIN sendmail[31192]: q8JJmQQV031192: from=, size=695, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1]
15 Sep 19 19:48:26 DOMAIN sendmail[31191]: q8JJmQ0D031191: q8JJmQ0E031191: DSN: User unknown
16 Sep 19 19:48:26 DOMAIN sendmail[31192]: q8JJmQQX031192: from=<>, size=2616, class=0, nrcpts=1, msgid=, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1]
17 Sep 19 19:48:26 DOMAIN sendmail[31191]: q8JJmQ0E031191: to=DOMAIN.com, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31719, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (q8JJmQQX031192 Message accepted for delivery)
20 Sep 19 19:48:26 DOMAIN sendmail[31193]: q8JJmQQX031192: to=, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=32817, dsn=2.0.0, stat=Sent
21 Sep 19 19:49:36 DOMAIN sendmail[31200]: q8JJnaxi031200: from=DOMAIN.com, size=698, class=0, nrcpts=1, msgid=, relay=DOMAIN.com@localhost

The solution that I have found to work is to modify /etc/mail/sendmail.mc and add the following to the very end:

define(`MAIL_HUB', `DOMAIN.com.')dnl
define(`LOCAL_RELAY', `DOMAIN.com.')dnl

Be sure to replace DOMAIN with your local domain.

Notice: The above define code entries start with a ` and end with a ‘. Make sure you copy+paste the above as it is, and modify the domain as it’s not the standard begin with a ` and end with a `.

After doing so, you’ll need to install sendmail-cf and run a reconfiguration with the following:

cd /etc/mail/
yum install sendmail-cf
/etc/mail/make

Lastly, restart sendmail:

service sendmail restart