月度归档：2016年10月

RHEL / Centos Linux 7: Change and Set Hostname Command

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On a CentOS Linux 7 server you can use any one of the following tool to manage hostnames:

 

  1. hostnamectl command : Control the system hostname. This is recommended method.
  2. nmtui command : Control the system hostname using text user interface (TUI).
  3. nmcli command : Control the system hostname using CLI part of NetworkManager.

Types of hostnames

The hostname can be configured as follows

  1. Static host name assigned by sysadmin. For example, “server1”, “wwwbox2”, or “server42.cyberciti.biz”.
  2. Transient/dynamic host name assigned by DHCP or mDNS server at run time.
  3. Pretty host name assigned by sysadmin/end-users and it is a free-form UTF8 host name for presentation to the user. For example, “Vivek’s netbook”.

Static – The static host name is traditional host which can be chosen by the user and is stored in /etc/hostname file.

Transient – The transient host name is maintained by kernel and can be changed by DHCP and mDNS.

Pretty – It is a free form UTF -8 host name for the presentation to the user.

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Mysql常见问题

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1.1 MySQL常见问题

1.Slave I/O: error connecting to master ‘backup@192.168.1.x:3306’-retry-time: 60 retries: 86400,Error_code:1045
解决方法:
从服务器上删除掉所有的二进制日志文件，包括一个数据目录下的master.info文件和hostname-relay-bin开头的文件。
master.info:：记录了Mysql主服务器上的日志文件和记录位置、连接的密码。

2. Errorreading packet from server: File ‘/home/mysql/mysqlLog/log.000001’ not found(Errcode: 2) ( server_errno=29)
解决方法:
由于主服务器运行了一段时间，产生了二进制文件，而slave是从log.000001开始读取的，删除主机二进制文件，包括log.index文件。

3.Slave SQL: Error ‘Table ‘xxxx’ doesn’t exist’ on query.Default database: ‘t591’.Query: ‘INSERT INTO `xxxx`(type,post_id,browsenum)
SELECT type,post_id,browsenum FROM xxxx WHEREhitdate=’20090209”, Error_code: 1146

解决方法：
由于slave没有此table表，添加这个表，使用slave start 就可以继续同步。 继续阅读 →

How to install mod_ruby and eruby on Linux server

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mod_ruby embeds the Ruby interpreter into the Apache web server, allowing Ruby CGI scripts to be executed natively. These scripts will start up much faster than without mod_ruby.

1. Install eRuby & mod_ruby1) Install eRuby:

# wget http://www.modruby.net/archive/eruby-1.0.5.tar.gz
# tar -xzvf eruby-1.0.5.tar.gz
# cd eruby-1.0.5/
# ./configure.rb –with-charset=euc-jp –enable-shared
# make; make install

2) Install mod_ruby

i)Download latest mod_ruby tar file
# wget http://www.modruby.net/archive/mod_ruby-1.2.6.tar.gz
# tar -xzvf mod_ruby-1.2.6.tar.gz
# cd mod_ruby-1.2.6/
#  ./configure.rb –enable-eruby –with-apxs=/usr/local/apache/bin/apxs
# make; make install

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ext4 file systems and the 16 TB limit – how to *solve* it

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File systems do have limits. Thats no surprise. ext3 had a limit at 16 TB file system size. If you needed more space you´d have to use another file system for instance XFS or JFS or spilt the capacity into multiple mount points.

ext4 was designed to allow far more larger file systems than ext3. According to wikipedia ext4 has a maximum file system size of 1 EiB (approx. one exabyte or 1024 PB or 1024*1024 TB).

Now if you´d try to create one single large file system with ext4 on every linux distribution out there (including OEL 6.1; as of 18th August 2011) you will end up with:

[root@localhost ~]# mkfs.ext4 /dev/iscsi/test mke4fs 1.41.9 (22-Aug-2009)
mkfs.ext4: Size of device /dev/iscsi/test too big to be expressed in 32 bit susing a blocksize of 4096.

This post is about how to solve the issue. 继续阅读 →