Check if / Make a MySQL instance read only

January 8, 2013

To check if A DB is already in read only mode:

SELECT @@global.read_only;

To set ( at Runtime)

SET GLOBAL read_only=1;

To set permanently,  add the following in my.cnf

“read_only”

These options will  make the DB run  in a read only mode, except for the slave threads and the super users, who can still do writes.  This is used on slaves when you want to make sure only read requests are executed on slaves.

DEBIAN: Where is preinst, postinst, prerm, and postrm etc are stored AFTER installing the deb package

December 4, 2012

Ever had issues with uninstalling a package due to incorrect entries in prerm or postrm ?  Or do you like to have a look at  preinst, postinst, prerm, and postrm of an installed package?

You can find them here and make any corrections so that you are able to uninstall  the package.

ls /var/lib/dpkg/info/YOURPACKAGENAME

Find strings in one file which are not present in another file

November 16, 2012

When there is one string per line and they are not sorted, the simplest solution  would be:

grep -Ffx file2 -v file1

Debian :: Accessing lvm from single user mode

November 9, 2012

We have /usr mounted on lvm,  so it’s tricky to get the commands in
/usr/bin and /usr/sbin to work in single user mode. lvm devices wont
be loded by default.

lvm vgscan
lvm vgchange -ay
lvm lvs

Now you should see your normal LVM devices in /dev (example:
/dev/LVM-GROUP/LVM-VOLUME) . You can mount and use them.

How to find out which repository a package would be downloaded from – debian/ubuntu

June 12, 2012

apt-cache policy

Remove embedded album art

May 13, 2010

To remove embedded album art from music files from Ubuntu or variants, you can use eyeD3 which is in repository.

To install:

    apt-get install eyed3

To remove embedded album art :

    cd YOUR_MUSIC_DIR
    eyeD3 –remove-images * *.mp3
or
    eyeD3 –remove-images * *.ANY_OTHER_FORMAT

Find out what version of Ubuntu you’re using

August 28, 2008

Use this command:

lsb_release -a

in terminal

Troubleshooting Mailman + Sendmail – No mail going out to list members

August 28, 2008

This article is converted from the Mailman FAQ Wizard

Credits:
——————
Jacinta Richardson , Duncan Drury, Mark Sapiro and the other good folks at mailman-users mailing list
————————————————————————-

Here are some common things to check when no mail is going out from your lists.

Also, do you get no mail at all from Mailman or just no posts? If you get no posts but you do get some notifications, still check everything but focus more on items 1), 2), 3), 5), 6), 7) and if applicable 9).

In this article it’s assumed that you are using Sendmail as the MTA.

1. Check_perms. In all cases you should start by checking the permissions on the files that were setup:

~mailman/bin/check_perms

2. Cron/mailmanctl.
1. Mailman 2.0.x only – Make sure that the cron daemon is running

ps aux |grep cron |grep -v grep

This will print out the process information about the cron daemon. If it returns a blank line, then cron is NOT running. NOTE: Mailman 2.0.13 and lower does not run an independent daemon. The qrunner process is run via cron.
2. Mailman 2.1.x – Later versions of Mailman, versions 2.1 and above, need cron for certain support jobs, but not for normal mail delivery. In Mailman 2.1.x there is an independent daemon called mailmanctl. You need to make sure that the mailmanctl daemon is also running

ps auxww| grep mailmanctl |grep -v grep

If this returns a blank line then the Mailman daemon is not running! Also, do

ps auxww | egrep ‘p[y]thon’

or

ps -fAww | egrep ‘p[y]thon’

or however you might spell it on your system. This should show that mailmanctl and eight qrunner processes are all running. See item 5) below.
3. Aliases. To create a mailman list you ran “newlist” and it printed out four (or ten) lines that you needed to copy to the /etc/aliases file (or wherever your MTA goes to find its aliases). Check that the aliases are in /etc/aliases:

grep wrapper /etc/aliases

Note for version 2.1: “wrapper” has been replaced with “mailman”,

grep mailman /etc/aliases

Even if the aliases are there, you may still need to reset the aliases hash table so that it includes this new alias information:

newaliases

Here is a typical alias listing for a group called “sys”:

## Mailman verion 2.0.x system mailing list
sys: “|/home/mailman/mail/wrapper post sys”
sys-admin: “|/home/mailman/mail/wrapper mailowner sys”
sys-request: “|/home/mailman/mail/wrapper mailcmd sys”
sys-owner: sys-admin

And here’s a typical list of aliases for the ‘mailman’ list in mailman 2.1.x.

## mailman mailing list
mailman: “|/usr/local/mailman/mail/mailman post mailman”
mailman-admin: “|/usr/local/mailman/mail/mailman admin mailman”
mailman-bounces: “|/usr/local/mailman/mail/mailman bounces mailman”
mailman-confirm: “|/usr/local/mailman/mail/mailman confirm mailman”
mailman-join: “|/usr/local/mailman/mail/mailman join mailman”
mailman-leave: “|/usr/local/mailman/mail/mailman leave mailman”
mailman-owner: “|/usr/local/mailman/mail/mailman owner mailman”
mailman-request: “|/usr/local/mailman/mail/mailman request mailman”
mailman-subscribe: “|/usr/local/mailman/mail/mailman subscribe mailman”
mailman-unsubscribe: “|/usr/local/mailman/mail/mailman unsubscribe mailman”

If you are using Sendmail with virtual domains, you will have to also add entries into the into the ‘virtusertable’ to make the mapping for the virtual domain to the local aliases previously setup, similiar to the following:

## mailman virtual mappings
sys@virtdomain.com sys
sys-admin@virtdomain.com sys-admin
sys-request@virtdomain.com sys-request
sys-owner@virtdomain.com sys-admin

then run ‘make’ or ‘makemap’ to rebuild the virtusertable.db file and restart sendmail. This solution is limited in that you can not have multiple virtual domain with the same local address/list name. NOTE: in mailman version 2.1 and above you may have a secondary aliases file that is used specifically for Mailman and the lists that it creates:

~mailman/data/aliases

You will need to make sure that this alias file isrecognized by your MTA (postfix, sendmail, etc), and that it is up-to-date with your latest aliases. If you do not have integration turned on, or you do not have this alias file, then all your aliases must go in the standard /etc/aliases file as specified above.
4. Smrsh. Check to see if your MTA uses smrsh. Red Hat as well as a few other distributions automatically setup Sendmail to use smrsh. Smrsh stops Sendmail from running a script or other program that is included in an alias. Mailman uses a program called “wrapper” to run all of its aliases (see the alias examples above):

grep “smrsh” sendmail.cf

If this comes up blank then Sendmail does not use smrsh and the rest of this section doesn’t apply – skip to 4); if not, then your server is probably running smrsh and you need to make sure that smrsh is setup to allow Mailman’s wrapper program to run. Locate the smrsh directory and do an ls -l of that directory. On Red Hat:

ls -l /etc/smrsh

and the output should be similar to:

wrapper -> /home/mailman/mail/wrapper

Note: some systems setup the smrsh directory in:

/usr/adm/sm.bin/

Note: to find the sm.bin directory try:

strings /usr/lib/smrsh | grep sm.bin

Note for version 2.1: the wrapper program is now simply called “mailman”,

mailman -> /var/mailman/mail/mailman

5. Interface. Some distributions in a noble “attempt” to limit the number of open relays on the internet, default Sendmail so that it listens to a limited number of interfaces. The default interface that Mailman list’s use is “localhost” (127.0.0.1) – this is configurable in Mailman’s mm_cfg.py file. To check Sendmail’s configuration file:

grep “Port” sendmail.cf

This will list out the DeamonPortOption and indicate the interfaces it listens on (0.0.0.0 would mean all interfaces). You can also check out which interfaces your MTA is listening on by using:

netstat -na |grep “:25 “

In a similar vein, some folks have reported that “localhost” is not defined in their /etc/hosts file (it should be set to 127.0.0.1). Also make sure /etc/hosts is world readable. Also see 4.73 How do I debug smtp-failure problems – delivery to user-example.com failed with code -1- and Low level smtp error-. The settings in ~mailman/Mailman/mm_cfg.py (or Defaults.py) that are used to set these “Delivery Defaults”:

DELIVERY_MODULE = ‘SMTPDirect’
MTA = ‘Manual’
SMTPHOST = ‘localhost’
SMTPPORT = 0 # default from smtplib
SENDMAIL_CMD = ‘/usr/lib/sendmail’

6. qrunner.
1. Mailman 2.0.x only – If you are running Mailman 2.0.x then qrunner is run every minute via a cron job (that is why cron must be running for Mailman to work). Try running the program by hand. The exact syntax can be found in Mailman’s cron jobs:

su mailman
crontab -l

Here is an example of running qrunner by hand:

su mailman
/usr/bin/python -S /home/mailman/cron/qrunner

If this generates any errors then send those to the list for diagnosis – or look at the last few lines of errors and search the list for key words from the error messages.
2. Mailman 2.1.x – If you are running Mailman 2.1.x then the qrunners are daemons that are started by $prefix/bin/mailmanctl, which itself may be being run via a ‘mailman’ startup script. This is described in the INSTALL document for the version of MM you are running. Note that there are eight qrunners. These runners and their functions are:

ArchRunner # messages for the archiver
BounceRunner # for processing of bounces
CommandRunner # commands and confirmations from the outside world
IncomingRunner # posts from the outside world
NewsRunner # outgoing messages to the nntpd
OutgoingRunner # outgoing messages to the smtpd
VirginRunner # internally crafted (virgin birth) messages
RetryRunner # retry temporarily failed deliveries

If you aren’t doing any gatwaying to usenet, you can do without NewsRunner, and if you aren’t archiving any lists, you can do without ArchRunner, but the other six are required to be running for normal Mailman operation. Also note that if any queues are ‘sliced’ there will be more than one runner for that queue, and you need them all. For example, if OutgoingRunner is set up for 4 slices, there will be four copies of OutgoingRunner processing slices 0:4, 1:4, 2:4 and 3:4. If any of these four is not running, its portion of the out queue will not be processed.
7. Locks. A errant lock file can stop a list from processing as Mailman waits for the lock to be removed. Since your list is not sending, we shall assume that no lock files should be on the list and that it is safe to delete any we find.
Note that we are talking here about locks with the list name as part of the lock file name. The master-qrunner locks are normal and are not the cause of non-delivery problems. On the contrary, if they
weren’t there it would indicate that the qrunners weren’t running.

ls -l ~mailman/locks

The output will be something like:

qrunner.lock.moya.trilug.org.22845

This indicates that process # 22845 created the lock. To look at this process and see what it is (if it still exists):

ps aux |grep 22845 |grep -v grep

8. Logs. If you don’t have any of the common problems above, then you should look for errors in your log files. First look for errors in your MTA log files. On Red Hat that would be in /var/log/maillog. Look in the log starting at the time you sent a test message. You should see your initial message come in and be passed on to your Mailman list, afterwards you may see warnings or errors caused by Mailman trying to send out mail to the members of the list.
Next look in Mailman’s logs. The files are in ~mailman/logs/ or usually /var/log/mailman on RedHat.
There are several logs to look in for problems:

error
smtp-failure
smtp
vette
config
post
qrunner

Note: if you look in the qrunner log you may see several warnings about “Could not acquire qrunner lock”, these are actually normal and are NOT a problem, but other messages about qrunners terminating and being restarted or not do indicate a problem.
Every line in the log files is dated so you should be able to isolate the place in the log files to start looking, based on when your problem started.
* What do the logs and the times of the entries in your MTA show. Is it passing the mail into the mailman alias properly? Check the time.
* Now check the Mailman post log and when it shows the message accepted for posting. The time should be very close to the MTA’s time.
* Now back to the MTA, does it show the message going out to the various folks on the list?
9. Qfiles. You may have a malformed email (or one that is simply too big) clogging up the flow of mail to your lists. Mail that is queued up by Mailman is stored in the directory:

~mailman/qfiles

or in FHS compliant RedHat systems

/var/spool/mailman

Move any files out of the directory and into a temporary directory, then send a new test message to your list. If that works, then you can move some of the old queued up files back and let those process. If it stops working again then you have a bad message in that batch – delete them or copy them to a different temporary directory.
Note that files accumulating in a queue directory can also mean that its qrunner (or one of its slice qrunners) is not running. See 1b and 5b above
10. SMTPHOST Mailman would accept messages but they wouldn’t go anywhere. logs/smtp would just show “All recipients refused: (61, ‘Connection refused’)”. My mailserver is configured to listen only on its external IP address, no localhost or anything like that. I had to add to ~mailman/Mailman/mm_cfg.py:

SMTPHOST = ”

After that Mailman started working perfectly.
11. Sendmail + mm-handler If your mail is not getting to the mailing list then try testing mm-handler independently of sendmail:

echo “From: jbloggs@hotmail.com
To: testlist@mailman.mydomain.com
Subject: Test
test mail body
” | /etc/mail/mm-handler mailman.mydomain.com \
-r jbloggs@hotmail.com testlist

To test with sendmail without your email client try:

echo “From: jbloggs@hotmail.com
To: testlist@mailman.mydomain.com
Subject: Test
test mail body
” | /usr/sbin/sendmail -fjbloggs@hotmail.com \
testlist@mailman.mydomain.com

Also try editing mm-handler and setting DEBUG=1 and rerun the sendmail command above and see if you get a bounce.
12. Topics If your list has topics defined, make sure users have appropriate settings to receive the posts they want.

If none of the above steps helps, then try seeking out help on the mailman-users@python.org mailing list. When submitting your problem to the list please include the following information:

* version of mailman you are running,
* how it was installed (via rpm, apt-get, or source),
* version of OS your server is running,
* the MTA (sendmail, postfix, exim, qmail, etc) running on your server.

As a courtesy to the good folks on the list please use a Subject that describes your problem (and not simply the word “Help).

How to create a list of installed packages in Ubuntu / Debian

August 15, 2008

dpkg –get-selections

How to do a syntax check of proftpd.conf file after making an edit.

August 14, 2008

To perform a syntax check of your proftpd.conf file, you can use the following command

$sudo proftpd -td5

or if you are logged in as root

#proftpd -td5


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