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Getting a core dump out of CentOS 7.2

Getting a core dump out of CentOS 7.2

Since Systemd took over as the main init system in Red Hat Linux and derrivatives like CentOS, it has become more difficult to get a core dump out of a daemon application. The traditional approach of running ulimit -c unlimited before executing the binary works when running the application from the command line but does nothing for a daemon managed by Systemd’s unit files.

There is a lot of misleading information online about how to solve this so I thought I’d add a correct solution to the mix in the hope that it’s helpful.

The suggestions I found online include editing /etc/security/limits.conf, adding LimitCore=infinity to the Unit file, and messing around with /etc/systemd/coredump.conf. None of these methods work without customising the kernel configuration first.

Systemd is not configured to handle core dumps by default on CentOS (and by extension RHEL) distributions. The default behaviour is to write to the file core in the process’s working directory, which for daemons is often the root directory.

The obvious problem here is that the daemon probably doesn’t have write access to the root directory (if running as a non-root user). If is possible to change the working directory with the Systemd unit directive WorkingDirectory=/var/run/XXX. This is typically used with RuntimeDirectory=XXX, which creates and manages the lifecycle of /run/XXX (/var/run is a symlink to /run). Unfortunately, we can’t write the core file to a RuntimeDirectory because it gets deleted when the application terminates.

The simplest solution I found is to overwrite the kernel core_pattern setting. This can be edited at runtime by echoing a new value into /proc/sys/kernel/core_pattern:

echo /tmp/core-%e-sig%s-user%u-group%g-pid%p-time%t > /proc/sys/kernel/core_pattern
This will force the kernel to write all core files during the current OS uptime to /tmp with the filename pattern specified. The core manpage has more information on the syntax.

This change will be lost when the machine reboots. To effect the change at kernel startup, you need to edit /etc/sysctl.conf or a file in /etc/sysctl.d/.

kernel.core_pattern=/tmp/core-%e-sig%s-user%u-group%g-pid%p-time%t
Our solution at work was to write a script to create a file in /etc/sysctl.d/ at machine image creation time, so that the config is always there when we roll out to different environments (int, test, live etc.)

It should go without saying that there is no particular reason to use /tmp. The output can be redirected to any location the process has permission to write to. A network share may be more appropriate in some cases.

There may be another solution using systemd-coredump, but it is not part of this release of CentOS (7.2) and not in the yum repository at this time.

October 11th, 2017 | Category: Centos RHEL 7 | Leave a comment

CentOS 6.9 Hadoop 2.7.2

CentOS 6.9 Hadoop 2.7.2

master 192.168.1.130
slave 192.168.1.131

master

[root@localhost ~]# vi /etc/hosts

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
127.0.0.1 localhost
192.168.1.130 master
192.168.1.131 slave

[root@localhost ~]# vi /etc/sysconfig/network

NETWORKING=yes
HOSTNAME=localhost.localdomain
NETWORKING=yes
HOSTNAME=master

slave

[root@localhost ~]# vi /etc/hosts

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
127.0.0.1 localhost
192.168.1.130 master
192.168.1.131 slave

[root@localhost ~]# vi /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=localhost.localdomain
NETWORKING=yes
HOSTNAME=slave

hostname your-hostname

selinux

master

[root@master ~]# vim /etc/selinux/config
SELINUX=enforcing

SELINUX=disabled

firewall

CentOS iptables

master

[root@master ~]# iptables -F; /etc/init.d/iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]
iptables -nvL

master

[root@master ~]# ssh-keygen

master

[root@master ~]# cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
[root@master ~]# scp ~/.ssh/authorized_keys slave:~/.ssh/
slave

[root@slave ~]# ls .ssh/
authorized_keys
master

[root@master ~]# ssh slave
[root@slave ~]# exit
[root@master ~]#

JDK

# java -version

[root@master ~]# wget http://download.Oracle.com/otn-pub/java/jdk/7u79-b15/jdk-7u79-linux-x64.tar.gz?AuthParam=1480051498_4f2fdb0325a457f4c7d33a69355b3560

[root@master ~]# mv jdk-7u79-linux-x64.tar.gz\?AuthParam\=1480051498_4f2fdb0325a457f4c7d33a69355b3560 jdk-7u79-linux-x64.tar.gz
[root@master ~]# tar zxvf jdk-7u79-linux-x64.tar.gz
[root@master ~]# mv jdk1.7.0_79 /usr/local/

[root@master ~]# vi /etc/profile.d/java.sh

export JAVA_HOME=/usr/local/jdk1.7.0_79
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/jre/lib/rt.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
[root@master ~]# source /etc/profile.d/java.sh
[root@master ~]# java -version
java version “1.7.0_79”
Java(TM) SE Runtime Environment (build 1.7.0_79-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

[root@master ~]# scp jdk-7u79-linux-x64.tar.gz slave:/root/
[root@master ~]# scp /etc/profile.d/java.sh slave:/etc/profile.d/
slave

[root@slave ~]# tar zxvf jdk-7u79-linux-x64.tar.gz
[root@slave ~]# mv jdk1.7.0_79 /usr/local/

[root@slave ~]# source /etc/profile.d/java.sh
[root@slave ~]# java -version
java version “1.7.0_79”
Java(TM) SE Runtime Environment (build 1.7.0_79-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

Hadoop

master

[root@master ~]# wget https://mirrors.tuna.tsinghua.edu.cn/apache/hadoop/common/hadoop-2.7.2/hadoop-2.7.2.tar.gz
[root@master ~]# tar zxvf hadoop-2.7.2.tar.gz
[root@master ~]# mv hadoop-2.7.2 /usr/local/
[root@master ~]# ls /usr/local/
bin games include lib libexec share etc hadoop-2.7.2 jdk1.7.0_79 lib64 sbin src
[root@master ~]# ls /usr/local/hadoop-2.7.2/
bin include libexec NOTICE.txt sbin etc lib LICENSE.txt README.txt share
[root@master ~]# mkdir /usr/local/hadoop-2.7.2/tmp /usr/local/hadoop-2.7.2/dfs /usr/local/hadoop-2.7.2/dfs/data /usr/local/hadoop-2.7.2/dfs/name
/usr/local/hadoop-2.7.2/tmp
/usr/local/hadoop-2.7.2/dfs?

[root@master ~]# ls /usr/local/hadoop-2.7.2/
bin etc lib LICENSE.txt README.txt share dfs include libexec NOTICE.txt sbin tmp
[root@master ~]# rsync -av /usr/local/hadoop-2.7.2 slave:/usr/local
slave

[root@slave ~]# ls /usr/local/hadoop-2.7.2
bin etc lib LICENSE.txt README.txt share dfs include libexec NOTICE.txt sbin tmp

Hadoop

master

[root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/core-site.xml
fs.defaultFS
hdfs://master:9000 hadoop.tmp.dir
file:/usr/local/hadoop-2.7.2/tmp io.file.buffer.size
131072

fs.defaultFS
NameNode ?HDFS MapReduce core-site.xml hdfs-site.xml

[root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/hdfs-site.xml

dfs.namenode.name.dir
file:/usr/local/hadoop-2.7.2/dfs/name dfs.datanode.data.dir
file:/usr/local/hadoop-2.7.2/dfs/data dfs.replication
1 dfs.namenode.secondary.http-address
master:9001 dfs.webhdfs.enabled
true

[root@master ~]# mv /usr/local/hadoop-2.7.2/etc/hadoop/mapred-site.xml.template /usr/local/hadoop-2.7.2/etc/hadoop/mapred-site.xml
[root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/mapred-site.xml

mapreduce.framework.name
yarn mapreduce.jobhistory.address
master:10020 mapreduce.jobhistory.webapp.address
master:19888

[root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/yarn-site.xml

yarn.nodemanager.aux-services
mapreduce_shuffle yarn.nodemanager.auxservices.mapreduce.shuffle.class
org.apache.hadoop.mapred.ShuffleHandler yarn.resourcemanager.address
master:8032 yarn.resourcemanager.scheduler.address
master:8030 yarn.resourcemanager.resource-tracker.address
master:8031 yarn.resourcemanager.admin.address
master:8033 yarn.resourcemanager.webapp.address
master:8088

[root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/hadoop-env.sh
export JAVA_HOME=${JAVA_HOME}
export JAVA_HOME=/usr/local/jdk1.7.0_79

[root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/yarn-env.sh

export JAVA_HOME=/usr/local/jdk1.7.0_79

root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/mapred-env.sh
# export JAVA_HOME=/home/y/libexec/jdk1.6.0/
export JAVA_HOME=/usr/local/jdk1.7.0_79

[root@master ~]# vi /usr/local/hadoop-2.7.2/etc/hadoop/slaves
localhost
slave

[root@master ~]# rsync -av /usr/local/hadoop-2.7.2/etc/ slave:/usr/local/hadoop-2.7.2/etc/

[root@master ~]# vi /etc/profile.d/hadoop.sh

export HADOOP_HOME=/usr/local/hadoop-2.7.2
export PATH=$HADOOP_HOME/bin:$HADOOP_HOME/sbin:$PATH

[root@master ~]# source /etc/profile.d/hadoop.sh
[root@master ~]# hadoop version
Hadoop 2.7.2
Subversion https://git-wip-us.apache.org/repos/asf/hadoop.git -r b165c4fe8a74265c792ce23f546c64604acf0e41
Compiled by jenkins on 2016-01-26T00:08Z
Compiled with protoc 2.5.0
From source with checksum d0fda26633fa762bff87ec759ebe689c
This command was run using /usr/local/hadoop-2.7.2/share/hadoop/common/hadoop-common-2.7.2.jar

[root@master ~]# scp /etc/profile.d/hadoop.sh slave:/etc/profile.d/
slave

hadoop

[root@slave ~]# source /etc/profile.d/hadoop.sh
[root@slave ~]# hadoop version
Hadoop 2.7.2
Subversion https://git-wip-us.apache.org/repos/asf/hadoop.git -r b165c4fe8a74265c792ce23f546c64604acf0e41
Compiled by jenkins on 2016-01-26T00:08Z
Compiled with protoc 2.5.0
From source with checksum d0fda26633fa762bff87ec759ebe689c
This command was run using /usr/local/hadoop-2.7.2/share/hadoop/common/hadoop-common-2.7.2.jar

Hadoop

master

[root@master ~]# /usr/local/hadoop-2.7.2/bin/hdfs namenode -format
[root@master ~]# echo $?
0

root@master ~]# /usr/local/hadoop-2.7.2/sbin/start-all.sh
[root@master ~]# jps
5560 ResourceManager
5239 NameNode
5631 Jps
5415 SecondaryNameNode
slave

[root@slave ~]# jps
5231 DataNode
5444 Jps
5320 NodeManager
master

web UI
master:50070 ?namenode datanode?
master:8088 ?Yarn?

[root@master ~]# cd /usr/local/hadoop-2.7.2/
[root@master hadoop-2.7.2]# bin/hadoop jar ./share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.2.jar pi 1

[root@master ~]# /usr/local/hadoop-2.7.2/sbin/stop-all.sh

127.0.0.1 localhost
192.168.229.130 master
192.168.229.131 slave

copyFromLocal: Cannot create directory /123/. Name node is in safe mode

[root@master ~]# /usr/local/hadoop-2.7.2/bin/hdfs dfsadmin -safemode leave

October 10th, 2017 | Category: Centos | Leave a comment

postfix admin

This article mainly describes the postfix common command and mail queue management:

Postfix has the following four message queues, are managed by the management of the process of unified management:

maildrop: local mail placed in maildrop, but also copied to incoming.
incoming: Places messages that are arriving at the queue or managing the process that have not yet been discovered.
active: places the queue management process has been opened and is ready to deliver the message, the queue has a length limit.
deferred: Place messages that can not be delivered. May be delayed sending mail
Start postfix

/usr/sbin/postfix start
Stop postfix

/usr/sbin/postfix stop
Check the postfix configuration file

/usr/sbin/postfix check
Displays the configuration information that Postfix currently takes effect

postconf -n
Re-read the postfix configuration file

/ usr / sbin / postfix reload
View messages in the queue:

mailq
postqueue -p
View the queue size

mailq | wc – l
postqueue -p | wc -l
View the contents of the message

postcat -q Queue_ID
Force the sending of messages in the queue

/ usr / sbin / postfix flush
postqueue -f
Suspended sending messages in the queue

postsuper – h Queue_ID
postsuper- h ALL deferred
Unblock sent messages

postsuper – H Queue_ID
postsuper -H ALL deferred
Rejoining the queue:

postsuper – r Queue_ID
postsuper -r ALL
Delete the specified message

postsuper -d Queue_ID
Empty the messages in the queue

postsuper -d ALL
# Delete the message in the queue (in the deferred list of messages, delete the mail file directly, you can see which letters were deleted):

postsuper – d ALL deferred
find / var / spool / postfix / deferred -type f -exec rm – vf {} \;
# find / var / spool / postfix / defer -type f -exec rm -vf {} \;
List all problem mail (currently all messages that can not be sent)

find / var / spool / postfix / deferred -type f -exec ls -l – time -style = +% Y-% m-% d_% H:% M:% S {} \;
Delete messages that have not been sent for 3 days

find / var / spool / postfix / deferred -type f -mtime + 3 -exec rm -f {} \;
Delete bounce records for more than 5 days of mail (more than 5 days in the “defer” list)

find /var/spool/postfix/defer -type f -mtime + 5 -exec rm -f {} \;

# Here are some related logs

View the system log:

tail -f / var / log / messages
Check the e-mail log: basically very comprehensive, almost all of the mail problems encountered can be handled by the log

tail -f / var / log / maillog
maildrop related

tail -f /var/log/maildrop.log
clamd related

tail -f / var / log / clamav / clamd.log
tail -f /var/log/clamav/freshclam.log

October 9th, 2017 | Category: Postfix | Leave a comment

Mariadb centos 7.4

Mariadb centos 7.4

vi /etc/yum.repos.d/Mariadb.repo

# MariaDB 10.1 CentOS repository list
# http://downloads.mariadb.org/mariadb/repositories/
[mariadb]
name = MariaDB
baseurl = http://yum.mariadb.org/10.1/centos7-amd64
gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDB
gpgcheck=1

yum -y install MariaDB-server MariaDB-client

systemctl start mysql.service

mysql_secure_installation

Enter current password for root (enter for none):

Set root password? [Y/n] y

New password:

Re-enter new password:

Remove anonymous users? [Y/n] y

Disallow root login remotely? [Y/n] n

Remove test database and access to it? [Y/n] y

Reload privilege tables now? [Y/n] y

firewall

firewall-cmd –state

not running?firewall

systemctl start firewalld

running

3306
firewall-cmd –zone=public –add-port=3306/tcp –permanent
firewall-cmd –reload

2. root MariaDB

Mariadb
mysql -uroot -p
use mysql;
Grant all on *.* to ‘root’@’%’ identified by ‘root@test123’ with grant option;
flush privileges;

October 9th, 2017 | Category: Centos RHEL 7, mariadb | Leave a comment

Docker issue x509: certificate has expired or is not yet valid

root@clusterserver3 ~]# docker pull centos
Using default tag: latest
Trying to pull repository docker.io/library/centos …
Pulling repository docker.io/library/centos
Error while pulling image: Get https://index.docker.io/v1/repositories/library/centos/images: x509: certificate has expired or is not yet valid
[root@clusterserver3 ~]# update-ca-trust extract

October 7th, 2017 | Category: Centos RHEL 7, Docker | Leave a comment

RabbitMQ installation deployment

RabbitMQ installation deployment

This article mainly introduces the installation of rabbitmq-server-3.6.12 deployment

# Check if the old version of the software has been installed

rpm-qa | grep erlang
rpm -qa | grep rabbitmq
# If yum installed before the rabbitmq may have the old version of the software, you need to uninstall and then install

yum remove erlang-R14B erlang-erts -y
# Configure rabbitmq required yum source (epel source)

su -c ‘ rpm -Uvh http: // download. Fedora project.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm ‘
# Install the specified version of rabbitmq

wget http: // www.rabbitmq.com/releases/erlang/erlang-19.0.4-1.el6.x86_64.rpm
wget http: // www.rabbitmq.com/releases/rabbitmq-server/v3.6.12/rabbitmq -server-3.6.12-1.el6.noarch.rpm
yum install erlang- 19.0 . 4 – 1 .el6.x86_64.rpm – y
yum install rabbitmq-server- 3.6 . 12 – 1 .el6.noarch.rpm -y
# Start rabbitmq and configure the boot from the start

service rabbitmq- server start
ps -ef | grep rabbitmq
chkconfig rabbitmq – server on
chkconfig –list rabbitmq-server
# Set the rabbitmq enabled feature

rabbitmq- plugins enable rabbitmq_management
service rabbitmq -server restart
# The default user password for the guest, you can create a new rabbitmq user and authorize

rabbitmqctl add_user admin 123456
rabbitmqctl set_user_tags admin administrator
rabbitmqctl set_permissions -p ” / ” admin ” . * ” ” . * ” ” . * ”
# Create other users nice

rabbitmqctl add_user nice 123456
rabbitmqctl add_vhost nice
rabbitmqctl set_user_tags nice administrator
rabbitmqctl set_permissions -p ” nice ” nice ” . * ” ” . * ” ” . * ”
Can visit: http: // IP: 15672

complete

October 1st, 2017 | Category: Centos RHEL 7 | Leave a comment

CentOS7 install iptables firewall

CentOS 7 default firewall is not iptables, but firewall

Install iptable iptable-service

# First check whether the installation of iptables
service iptables status
# install iptables
yum install-y iptables
# upgrade iptables
yum update iptables
# install iptables-services
yum install iptables-services

Disable / stop the built-in firewalld service

# Stop the firewalld service
systemctl stop firewalld
# Disable the firewalld service
systemctl mask firewalld

Set up existing rules

# View iptables existing rules
iptables -L-n
# first allow all, otherwise there may be a cup
iptables -P INPUT ACCEPT
# clear all default rules
iptables-F
# clear all custom rules
iptables-X
# all counters 0
iptables -Z
# Allows packets from the lo interface (local access)
iptables -A INPUT -i lo -j ACCEPT
# open 22 port
iptables -A INPUT -p tcp -dport 22 -j ACCEPT
# open 21 port (FTP)
-A -p TCP –dport the INPUT iptables 21 is -j ACCEPT
# open port 80 (the HTTP)
iptables -A 80 –dport the INPUT -p TCP -j ACCEPT
# open port 443 (the HTTPS)
iptables -A the INPUT -p TCP – -dport 443 -j ACCEPT
# Allow ping
iptables -A INPUT -p icmp –icmp-type 8 -j ACCEPT
# Allow the return data after the native request RELATED, which is set for FTP
iptables -A INPUT -m state –state RELATED, ESTABLISHED -j ACCEPT
# other inbound discarded
iptables -P INPUT DROP
# all outbound all green
iptables -P OUTPUT ACCEPT
# all forwarded
iptables -P FORWARD DROP

Other rules set

Iptables -P INPUT
-p tcp -s 45.96.174.68 -j ACCEPT
# Filter all requests that are not above rules
iptables -P INPUT DROP
# To block an IP, if you want to add an intranet ip trusted (accept all of its TCP requests) Use the following command:
iptables -I INPUT -s ***. ***. ***. *** -j DROP
# To unblock an IP, use the following command:
iptables -D INPUT -s * **. ***. ***. *** -j DROP

Save the rule settings

# Save the above rules
service iptables save

Open the iptables service

# Register iptables service
# equivalent to the previous chkconfig iptables on
systemctl enable iptables.service
# Open service
systemctl start iptables.service
# View status
systemctl status iptables.service

Solve vsftpd iptables open, can not use the passive mode of the problem

1. First modify or add the following in / etc / sysconfig / iptables-config

# Add the following, note that the order can not be exchanged
IPTABLES_MODULES = “ip_conntrack_ftp”
IPTABLES_MODULES = “ip_nat_ftp”

2. Reset the iptables settings

iptables -A INPUT -m state –state RELATED, ESTABLISHED -j ACCEPT

The following is a complete setup script

#! / bin / SH
iptables -P the INPUT ACCEPT
iptables -F
iptables the -X-
iptables the -Z
iptables -A the INPUT LO -i -j ACCEPT
iptables -A –dport 22 is the INPUT -p TCP -j ACCEPT
iptables -A the INPUT -p tcp –dport 21 -j ACCEPT
iptables -A INPUT -p tcp –dport 80 -j ACCEPT
iptables -A INPUT -p tcp –dport 443 -j ACCEPT
iptables -A INPUT -p icmp –icmp-type 8 – j ACCEPT
iptables -A INPUT -m state –state RELATED, ESTABLISHED -j ACCEPT
iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP
service iptables save
systemctl restart iptables.service

October 1st, 2017 | Category: Centos RHEL 7 | Leave a comment

CentOS 7 installs MySQL5.7.19

Environment: Virtual Machine + CentOS 7

1. download binary package, the following mysql-5.7.19-linux-glibc2.12-x86_64.tar.gz link is the official website

cd /usr/local/src

wget https://dev.mysql.com/get/Downloads/MySQL-5.7/mysql-5.7.19-linux-glibc2.12-x86_64.tar.gz
2. extract, rename

[root@beta src]# tar zxvf mysql-5.7.19-linux-glibc2.12-x86_64.tar.gz

[root@beta src]# ls
index.html?id=471614 mysql-5.7.19-linux-glibc2.12-x86_64 mysql-5.7.19-linux-glibc2.12-x86_64.tar.gz
[root@beta src]# mv mysql-5.7.19-linux-glibc2.12-x86_64 /usr/local/mysql
3. Initialize

[root@beta mysql]# useradd -M -s /sbin/nologin mysql

[root@beta mysql]# ls
bin COPYING docs include lib man README share support-files
[root@beta mysql]# mkdir -p /usr/local/mysql/data/mysql
[root@beta mysql]# chown mysql /usr/local/mysql/data/mysql
The following step attention to the last sentence:

[root@beta mysql]# ./bin/mysqld –initialize –user=mysql –datadir=/usr/local/mysql/data/mysql
2017-09-27T03:44:47.999985Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use –explicit_defaults_for_timestamp server option (see documentation for more details).
2017-09-27T03:44:49.011240Z 0 [Warning] InnoDB: New log files created, LSN=45790
2017-09-27T03:44:49.180334Z 0 [Warning] InnoDB: Creating foreign key constraint system tables.
2017-09-27T03:44:49.245777Z 0 [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: 3649ce8c-a336-11e7-a43f-000c292b2832.
2017-09-27T03:44:49.266053Z 0 [Warning] Gtid table is not ready to be used. Table ‘mysql.gtid_executed’ cannot be opened.
2017-09-27T03:44:49.268172Z 1 [Note] A temporary password is generated for root@localhost: ADB&yGx-d8ab

ADB&yGx-d8ab
Then execute:

[root@beta mysql]# ./bin/mysql_ssl_rsa_setup –datadir=usr/local/mysql/data/mysql
Generating a 2048 bit RSA private key
………………….+++
…+++
writing new private key to ‘ca-key.pem’
—–
Generating a 2048 bit RSA private key
…………………….+++
…………………………………………………………………….+++
writing new private key to ‘server-key.pem’
—–
Generating a 2048 bit RSA private key
………………..+++
…………………..+++
writing new private key to ‘client-key.pem’
4. Copy the configuration file and startup script

First check whether there is /etc/my.cnf, if not

cp support-files/my-default.cnf /etc/my.cnf
Edit /etc/my.cnf, focus on the following changes, the other as far as possible comment out:

basedir = /usr/local/mysql
datadir = //usr/local/mysql/data/mysql
socket = /tmp/mysql.sock
2. Start the script

cp support-files/mysql.server /etc/init.d/mysqld
Edit /etc/init.d/mysqld, only modify the following:

basedir=/usr/local/mysql
datadir=/data/mysql
Add /etc/init.d/mysqld to the startup item:

[root@beta mysql]# chkconfig –add mysqld
[root@beta mysql]# chkconfig –list

systemd ‘systemctl list-unit-files’?
target
systemctl list-dependencies [target]?

5. Start the service

/etc/init.d/mysqld start
6. Set the root password

Log in with the initial password (see step 3 above)

/usr/local/mysql/bin/mysql -uroot -p‘’ #-p?’’
Appears mysql>, enter set password = password (‘new password’);

Exit, login with new password

2. Forget the initial password

To /etc/my.cnf/[mysqld] Add a line below skip-grant-tables, restart mysqld: /etc/init.d/mysqld restart

[mysqld]
skip-grant-tables
basedir=/usr/local/mysql
datadir=/usr/local/mysql/data/mysql
socket=/tmp/mysql.sock

[root@beta ~]# /etc/init.d/mysqld restart
Shutting down MySQL.. SUCCESS!
Starting MySQL.. SUCCESS!
Re-login mysql:

[root@beta ~]# /usr/local/mysql/bin/mysql -uroot
mysql> enter: update mysql.user set authentication_string = password (‘123333’) where user = ‘root’;

mysql> update mysql.user set authentication_string=password(‘123333′) where user=’root’;
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 1
Quit, delete my.cnf added skip-grant-tables, restart mysqld

New password re-login mysql:

[root@beta ~]# /usr/local/mysql/bin/mysql -uroot -p’123333′
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 5.7.19 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.

mysql>

October 1st, 2017 | Category: Centos, Centos RHEL 7 | Leave a comment

Tomcat commonly used in the tuning

Tomcat commonly used in the tuning

In the usual use of Apache, Nginx or other related to the provision of Web services software has a corresponding performance module tuning changes, and in Tomcat also has a corresponding performance tuning modified configuration, here is simply to say more commonly used Several Tomcat in the performance tuning configuration parameters in the Tomcat tuning parameters can be divided into two parts: 1, in the Tomcat binary folder bin directory catalina.sh or catalina.bat add modify configuration tomcat Use the operating parameters; 2, in the Tom folder conf folder configuration changes server.xml in the container.

One, tomcat use the operating parameters catalina.sh tuning

Modify the catalina.sh script, add the modified JAVA_OPTS variable Parameters:
JAVA_OPTS = “$ JAVA_OPTS -Xms3072m -Xmx3072m -Xmn1536m \
-XX: PermSize = 384m -XX: MaxPermSize = 384m -XX: + UseConcMarkSweepGC \
-XX: + UseCMSCompactAtFullCollection -XX : CMSMaxAbortablePrecleanTime = 500 \
-XX: + CMSClassUnloadingEnabled -XX: + CMSClassUnloadingEnabled -Djava.util.logging.manager = org.apache.juli.ClassLoaderLogManager ”

-server: tomcat default is a java -client model to run, the server means that your tomcat is the real production mode in the operation of the better performance
-Xms-Xmx: JVM memory settings, JVM initial The allocated heap memory is specified by -Xms and defaults to 1/64 of the physical memory. The maximum allocated heap memory for the JVM is specified by -Xmx, which is 1/4 of the physical memory by default. When the default free heap memory is less than 40%, the JVM will increase the heap until the maximum limit of -Xmx. When the
free heap memory is greater than 70%, the JVM will reduce the heap until the minimum limit of -Xms. It is recommended to set the maximum and minimum Conducive to the JVM garbage collection mechanism
-Xmn: set the new generation, the size of the heap = new generation size + older generation size + lasting generation size. This value has a significant impact on system performance. Sun’s official recommendation for the entire heap 3/8
-XX: Whenever the JDK version is upgraded, your JVM will use the latest addition of the optimization technology –
XX: PermSize: set non-heap memory initial Value, the default is the physical memory of the 1/64
-XX: MaxPermSize: set the eternal generation memory initial size, that is, the maximum non-heap memory size, the default is the physical memory 1 /
4XX: + UseConcMarkSweepGC: CMS gc, this feature Only jdk1.5 that follow-up version has the function, it uses the gc estimate trigger and heap occupancy trigger
-XX: + UseCMSCompactAtFullCollection: in the case of the use of concurrent gc, to prevent memoryfragmention, the live object to organize the memory fragments to reduce
-XX: + UseParNewGC: on the new generation of multi-threaded parallel recovery, so close fast-
XX: + CMSClassUnloadingEnabled: CMS collector will not be the default generation of garbage collection
-XX: CMSMaxAbortablePrecleanTime: CMS GC needs to go through more steps to complete a GC action, in the case of minor GC more frequent, it is likely to cause the CMS GC has not yet completed, resulting in concurrent mode failure, you can-xX: CMSMaxAbortablePrecleanTime set Small values ??to ensure that CMS GC completes object recovery as soon as possible and avoids concurrent mode failure, especially in versions of JDK 5.0 +, 6.0+ on CMS-concurrent-abortable-preclean-start and CMS-concurrent-abortable -preclean These two steps may take a long time, resulting in the recovery of the old generation of objects for a long time before being recovered, this is a Sun JDK CMS GC bug

Second, Tomcat server.xml configuration file

The common configuration performance tuning configuration in Tomcat is as follows:

connectionTimeout: timeout time in milliseconds, the default value is 60000, that is, 60 seconds
maxThreads: tomcat: the maximum number of threads starting, the default value of 200
minSpareThreads: Tomcat initialization to create the number of threads. Default value 4
maxProcessors: Tomcat runtime to create the maximum number of threads, the default value of 75, generally based on the actual production environment to modify
acceptCount: tomcat started when the maximum number of threads to accept the number of queued requests, the default value of 100, web server allows the maximum number of connections is also subject to the operating system kernel parameter settings, usually Windows is about 2000, Linux is about 1000, usually the same as the value set
maxThreads enableLookups: whether the anti-check domain name, the default value is true. In order to improve the processing power, should be set to false
compression: compressed transmission, the value on / off / force, the default value off
redirectPort: SSL redirect port, the default 8443

In short, in the usual need to modify the actual production conditions, Tomcat reasonable performance tuning, Tomcat will be the overall performance will be greatly improved.

October 1st, 2017 | Category: tomcat | Leave a comment

Enable linux root access on Microsoft Azure Cloud

Enable linux root access on Microsoft Azure Cloud

How to enable linux root access on Microsoft Azure Cloud
1. Login via ssh using your sudo user on your Microsoft Azure linux server
2. Now login as root user
1 Lines

[root@mohan ~]# sudo su –
3. check if root access is set (LOCK means that root access is disabled)
1 Lines

[root@mohan ~]# grep root /etc/shadow
Result:
root:*LOCK*:14600::::::
4. enable root access (as root user enter command passwd)
1 Lines

[root@mohan ~]# passwd
5. Now enter your password and root access is enabled.
You can check this by using command “grep root /etc/shadow”
That’s all folks

1. Login via ssh using your sudo user
2. Now login as root user
Code: [Select]
sudo su –

3. check if root access is set (LOCK means that root access is disabled)
Code: [Select]
[root@Linux ~]# grep root /etc/shadow
root:*LOCK*:14600::::::

4. enable root access (as root user enter command passwd)
Code: [Select]
[root@Linux ~]# passwd

now enter your password and root access is enabled, you can check this by using command “grep root /etc/shadow”

September 28th, 2017 | Category: Centos RHEL 7 | Leave a comment
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