Category: Linux Command

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Managing The Postfix Queue

In this article, I will go over the tools Postfix offers you to manage the mail queue. There are 6 actions you can perform on messages in the queue.

  • List messages.
  • Delete messages.
  • Hold messages.
  • Re-queue messages.
  • Display the contents of messages.
  • Flush the messages in the queue.

Listing Messages in the Postfix Queue

Postfix provides a tool called postqueue. The command provided with the -p switch will display an entry for each message in the queue. The output will include a column for the message ID, size, arrival time, send, and recipient addresses.

Messages that are currently in the active queue will display a asterisk to the right of the message ID.

If there is a message in the hold queue, it will display a exclamation point to the right of the message ID.

If a message is deferred, there will not be symbol / mark to the right of the message ID.

postqueue -p

-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------  
5866DAC07F3 362 Sat Oct 12 15:53:56 trankin@tullyr.com  
(connect to mail.tullyr.com[208.70.75.100]:25: Connection refused)  
<trankin@tullyr.com>

Deleting Messages in the Postfix Queue

To delete messages from the Postfix queue, you can use the postsuper command. The postsuper tool can be used to delete a single message, or all messages in the queue.

To delete a single message from the queue, provide the -d switch followed by the message ID.

postsuper -d 5866DAC07F3

When you want to delete all messages in the queue, you provide postsuper with the word ALL in all capitals instead of the message ID.

postsuper -d ALL

NOTE – Be careful when using the postsuper command with the -d ALL switch. This command will delete all messages in the queue immediately without prompting you for verification.

Holding Messages in the Postfix Queue

The Postfix hold queue provides a place for messages to be held indefinitely. If you move a message into the hold queue, it will not be delivered until you specifically remove it or move it back into the normal queue processing.

To place a message in the hold queue, you use the tool postsuper with the -h switch followed by message ID.

postsuper -h 5866DAC07F3

When you need to move a messae back into the normal queue for processing, you use the postsuper command with the -H switch followed by the message ID.

postsuper -H 5866DAC07F3

Re-queue Messages in the Postfix Queue

If you have messages that are incorrect based on a misconfigured Postfix installation, you may need to re-queue the messages via the postsuper command. Some example of bad messages could be problems such as incorrect transport type, incorrect rewriting of an address, or an incorrect next hop.

After fixing the Postfix configuration, you can re-queue a single message or all messages. To requeue a message, you will use the postsuper command with the -r switch. When this command is run, it will update the incorrect information based on the new configuration.

To re-queue a single message you pass the message ID as in the example below.

postsuper -r 5866DAC07F3

If you need to re-queue all messages, you can pass the capital word ALL.

postsuper -r ALL

Displaying the Contents of Messages in the Postfix Queue

If you need to view the contents of a message in the queue, Postfix provides the postcat tool for this. The postcat tool will display the contents of a file when provided with the -q switch followed by the message ID.

postcat -q 5866DAC07F3

Flushing Messages in the Postfix Queue

If you have messages in the queue that you would like to flush, you can use the postqueue command with the -f switch. Flushing the queue will cause Postfix to attempt to deliver all messages in the queue immediately.

postqueue -f

There are times when this is needed. However, it’s usually not a good idea to flush all of the messages in the queue. If you do this a lot, it can have an impact on the performance on your mail server. You should leave the queue management to the Postfix queue manager.

With Postfix, it’s possible to flush only those messages that are going to a specific domain. You can do this with the -s switch provided by postqueue. However, to do this the domain must be eligible for fast flush.

For a domain to be eligible for fast flush, it must be listed in the fast_flush_domains parameter. In Postfix, the default value for the fast_flush_domains includes all of the hosts that are listed in relay_domains.

To add the site to the fast_flush_domains you can append it to the line fast_flush_domains as shown below:

fast_flush_domains = $relay_domains tullyrankin.com

Now if you want to flush mail that is destined for the domain you added to the fast_flush_domains, you can use the postqueue command with the -s option as shown below:

postqueue -s tullyrankin.com
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Incorrect definition of table mysql.event: expected column ‘sql_mode’

[ERROR] Incorrect definition of table mysql.event: expected column ‘sql_mode’ at position 14

to have type set(‘REAL_AS_FLOAT’,’PIPES_AS_CONCAT’,’ANSI_QUOTES’,’IGNORE_SPACE’,’IGNORE_BAD_TABLE_OPTIONS’,’ONLY_FULL_GROUP_BY’,’NO_UNSIGNED_S

UBTRACTION’,’NO_DIR_IN_CREATE’,’POSTGRESQL’,’ORACLE’,’MSSQL’,’DB2′,’MAXDB’,’NO_KEY_OPTIONS’,’NO_TABLE_OPTIONS’,’NO_FIELD_OPTIONS’,’MYSQL323′,’M

YSQL40′,’ANSI’,’NO_AUTO_VALUE_ON_ZERO’,’NO_BACKSLASH_ESCAPES’,’STRICT_TRANS_TABLES’,’STRICT_ALL_TABLES’,’NO_ZERO_IN_DATE’,’NO_ZERO_DATE’,’INVAL

ID_DATES’,’ERROR_FOR_DIVISION_BY_ZERO’,’TRADITIONAL’,’NO_AUTO_CREATE_USER’,’HIGH_NOT_PRECEDENCE’,’NO_ENGINE_SUBSTITUTION’,’PAD_CHAR_TO_FULL_LEN

GTH’,’EMPTY_STRING_IS_NULL’,’SIMULTANEOUS_ASSIGNMENT’), found type set(‘REAL_AS_FLOAT’,’PIPES_AS_CONCAT’,’ANSI_QUOTES’,’IGNORE_SPACE’,’IGNORE_B

AD_TABLE_OPTIONS’,’ONLY_FULL_GROUP_BY’,’NO_UNSIGNED_SUBTRACTION’,’NO_DIR_IN_CREATE’,’POSTGRESQL’,’ORACLE’,’MSSQL’,’DB2′,’MAXDB’,’NO_KEY_OPTIONS

‘,’NO_TABLE_OPTIONS’,’NO_FIELD_OPTIONS’,’MYSQL323′,’MYSQL40′,’ANSI’,’NO_AUTO_VALU

Apr 26 04:22:08 mail mysqld: 2020-04-26  4:22:07 0 [ERROR] mysqld: Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.

i solved copying from the log file how the column has to be set and run this in the mysql db:

ALTER TABLE `event` CHANGE `sql_mode` `sql_mode` SET(‘REAL_AS_FLOAT’,’PIPES_AS_CONCAT’,’ANSI_QUOTES’,’IGNORE_SPACE’,’IGNORE_BAD_TABLE_OPTIONS’,’ONLY_FULL_GROUP_BY’,’NO_UNSIGNED_SUBTRACTION’,’NO_DIR_IN_CREATE’,’POSTGRESQL’,’ORACLE’,’MSSQL’,’DB2′,’MAXDB’,’NO_KEY_OPTIONS’,’NO_TABLE_OPTIONS’,’NO_FIELD_OPTIONS’,’MYSQL323′,’MYSQL40′,’ANSI’,’NO_AUTO_VALUE_ON_ZERO’,’NO_BACKSLASH_ESCAPES’,’STRICT_TRANS_TABLES’,’STRICT_ALL_TABLES’,’NO_ZERO_IN_DATE’,’NO_ZERO_DATE’,’INVALID_DATES’,’ERROR_FOR_DIVISION_BY_ZERO’,’TRADITIONAL’,’NO_AUTO_CREATE_USER’,’HIGH_NOT_PRECEDENCE’,’NO_ENGINE_SUBSTITUTION’,’PAD_CHAR_TO_FULL_LENGTH’,’EMPTY_STRING_IS_NULL’,’SIMULTANEOUS_ASSIGNMENT’) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT ”;

 

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SeaFile installation

create the 3 databases

c3ccnetdb
c3seafiledb
c3seahubdb

SELECT concat(‘DROP TABLE CASCADE IF EXISTS `’, table_name, ‘`;’)
FROM information_schema.tables
WHERE table_schema = ‘c3ccnetdb’;

pgrep -f seafile-controller
pgrep -f “seahub”
pkill -f seafile-controller
pkill -f “seahub”
mysql -u c3seafile -p c3ccnetdb < ./drop_all_tables.sql

in the directory where you want to install seafile

rm ./* -Rf
wget https://download.seadrive.org/seafile-server_7.0.5_x86-64.tar.gz
tar -xzf seafile-server_*
mkdir installed
mv seafile-server_* installed
cd seafile-server-*
./setup-seafile-mysql.sh
c3ccnetdb
c3seafiledb
c3seahubdb
./seafile.sh start
./seahub.sh start

create the certificates for https

vim ../conf/ccnet.conf
SERVICE_URL = https://seafile.saic.it
vim ../conf/seahub_settings.py
FILE_SERVER_ROOT = ‘https://www.myseafile.com/seafhttp’
./seafile.sh restart
./seahub.sh restart

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ERROR: Cannot uninstall a distutils installed

During this  command : pip install pillow moviepy

I’ve this error:

ERROR: Cannot uninstall ‘requests‘. It is a distutils installed project and thus we cannot accurately determine which files belong to it which would lead to only a partial uninstall.

to fix run :

pip install –ignore-installed requests

then again

pip install pillow moviepy

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The commands to check CentOS version

The following table contains most common and recommended ways on how to check CentOS version on your CentOS Linux server or desktop.

Command Description
$ rpm -q centos-release CentOS version valid for CentOS 6 and higher. Causes to reveal major, minor and asynchronous CentOS version.
$ lsb_release -d Requires redhat-lsb package to be installed before execution.
$ rpm -E %{rhel} RPM macro to reveal a major CentOS version
$ rpm –eval %{centos_ver} RPM macro to display a major version of CentOS
$ cat /etc/centos-release Linux cat command to output content of the /etc/centos-release to query CentOS version. Works with CentOS 6 and higher.

In case the above-provided commands did not help you to obtain the CentOS version number you may try the following alternative commands.

Although available only for CentOS version 7 and above the hostnamectl command might provide you with a significant clue about your OS version number:

$ hostnamectl 
   Static hostname: localhost.localdomain
         Icon name: computer-vm
           Chassis: vm
        Machine ID: fe069af6a1764e07be909d7cf64add99
           Boot ID: b81bb73dc549484c8927e830e149eb55
    Virtualization: kvm
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-862.6.3.el7.x86_64
      Architecture: x86-64

For more answers try to query all release files within the /etc directory:

$ cat /etc/*elease
CentOS Linux release 7.5.1804 (Core) 
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

CentOS Linux release 7.5.1804 (Core) 
CentOS Linux release 7.5.1804 (Core)

Bash Script to check CentOS version

The following bash script can be used to obtain the CentOS version number given that the /etc/centos-release file exists and is populated.

The below script serves as an example, feel free to modify wherever appropriate. For more information about Bash Scripting visit our bash scripting tutorial:

#!/bin/bash

full=`cat /etc/centos-release | tr -dc '0-9.'`
major=$(cat /etc/centos-release | tr -dc '0-9.'|cut -d \. -f1)
minor=$(cat /etc/centos-release | tr -dc '0-9.'|cut -d \. -f2)
asynchronous=$(cat /etc/centos-release | tr -dc '0-9.'|cut -d \. -f3)

echo CentOS Version: $full
echo Major Relase: $major
echo Minor Relase: $minor
echo Asynchronous Relase: $asynchronous

Output:

$ ./check-centos-version.sh 
CentOS Version: 7.5.1804
Major Relase: 7
Minor Relase: 5
Asynchronous Relase: 1804

Python program to check CentOS version

The following python script will output the distribution name along with the OS version number:

#!/usr/bin/python

import platform
print platform.linux_distribution()

Alternatively, one can execute python code directly from the shell:

$ python -c 'import platform; print platform.linux_distribution()'

Output:

$ python check-centos-version.py 
('CentOS Linux', '7.5.1804', 'Core')