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Base64 decode string with Perl on the command line.

perl -MMIME::Base64 -ne 'print
> decode_base64("PGRpdj4tLTxicj5UaGVzZSBIVE1MHNpZ25hdHVyZXMgYXJlIGdyZWF0Ljxicj48L2Rpdj4=")'

Zimbra stores mail signatures base64 encoded in the directory as objectClass zimbraSignature.

If you just need something quick, opinionatedgeek.com will do it for you.

Zimbra uses the LMTP protocol for inbound mailstore delivery. By default, Zimbra's Postfix MTA will use DNS for mailbox server host resolution. Use this tip to bypass DNS inbound delivery from the MTA to mailstore.

$ su - zimbra

Query the existing Postfix value
$ postconf lmtp_host_lookup
lmtp_host_lookup = dns

Edit /etc/hosts
10.1.1.1 mailstore.server.com

Modify main.cf
$ postconf -e lmtp_host_lookup=native

Update Zimbra's local configuration for upgrade persistence

By default, mail sent using the PHP mail() function will contain an envelope sender address consisting of the server's fully qualified domain name (FQDN). This can cause mail originating from apps like Drupal or MediaWiki that use PHP mail() for notifications to be filtered by mail servers rejecting sender domains not having an MX record.

Release 5.0.9_GA_2533.UBUNTU6 UBUNTU6 NETWORK edition

You are becoming a more esteemed Zimbra admin, but are tired of manually fetching environment variables from zmlocalconfig. Simply put the values into your shell environment.

su - zimbra
source ~/bin/zmshutil
zmsetvars

Now you can run your ldapsearch command like this:
ldapsearch -x -H $ldap_master_url -D $zimbra_ldap_userdn -w $zimbra_ldap_password "(cn=*)"

All values in "seconds" is the number of seconds from Epoch, Jan 1, 1970.

1. Current time in seconds.
   date +%s
1220815239
2. Convert 1220815239 seconds to a human readable date.
   date -d @1220815239
Sun Sep 7 15:20:39 EDT 2008
3. Convert 1220815239687 milliseconds to a human readable date.
   date -d @$[1220815239687/1000]
Sun Sep 7 15:20:39 EDT 2008

At times, it is necessary to increase the number of open files for a particular service user. For example, if you see this in your MySQL .err log:

080723 2:41:04 [ERROR] Error in accept: Too many open files

To fix, increase the number of open files for your mysqld user. Mine is mysql.

Check the system's maximum open file limit

# cat /proc/sys/fs/file-max

If this value is too low, increase it

# echo 81920 > /proc/sys/fs/file-max

Now, edit /etc/security/limits.conf to increase limits for the mysql user

tcpdump is a great tool for protocol traffic analysis and troubleshooting. I'm sure by now you know you need it, but you just need to know how to effectively use it. This post will be updated ongoing.

Have a look here http://dmiessler.com/study/tcpdump_recipes/. You'll find some great tips on tcpdump and other things nix.

1. man tcpdump
2. tcpdump -AvvvSs 1500 -i eth0 host 10.10.10.1
   

While

Counting to 3 and doing something along the way right on the command line.


# i=1; while [ "$i" -lt 4 ]; do echo $i; i=$(($i+1)); done
1
2
3


The same command in a script:

#!/bin/bash
i=0
while [ "$i" -lt 10 ]
do
   echo $i
   i=$(($i+1))
done


For

Iterate through lines in a file with a for loop on the command line.


# for a in $(cat /tmp/users); do echo $a; done
usera
userb


In a script:

#!/bin/bash
for a in $(cat /tmp/users)
do

ISO filesystems are helpful for creating disk images for burning CDs.

On Nix:

If you have a DMG file you would like to convert to an ISO, you might find this article helpful on macosxhints.com:

Here is how attachments show up in drupal. Anonymous users aren't going to see the attachment.