SSHd server not starting at boot RHEL / CentOS 7

By default sshd server does not start in CentOS 7.
chkconfig command does not control ssh daemon any more.

Solution is to use systemctl:

[code]
> systemctl enable sshd
[/code]

It produces following awkward result:
ln -s ‘/usr/lib/systemd/system/sshd.service’ ‘/etc/systemd/system/multi-user.target.wants/sshd.service’

To check if SSH server is staring on boot (and if it is running):

[code]
> systemctl status sshd

sshd.service – OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled)
Active: active (running) since Mon 2014-11-03 18:43:56 GMT; 20min ago
[/code]

Enabled – means it will start at boot time automatically.
Welcome to systemd world..

Alias interfaces in CentOS 7/ RHEL 7

[root@localhost ~]# cat /etc/sysconfig/network-scripts/ifcfg-enp3s0

HWADDR=00:15:80:99:A6:21
TYPE=Ethernet
BOOTPROTO=none
IPADDR0=212.47.x.x
NETMASK0=255.255.255.0
GATEWAY0=212.47.x.x
DEFROUTE=yes
PEERDNS=yes
PEERROUTES=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=no
IPV6_FAILURE_FATAL=no
NAME=enp3s0
IPADDR1=212.47.x.x
NETMASK1=255.255.255.0
IPADDR2=212.47.x.x
NETMASK2=255.255.255.0
IPADDR3=212.47.x.x
NETMASK3=255.255.255.0

UUID=a3fe28da-5d35-4885-9fe8-cb716c29b35a
ONBOOT=yes

Remove skype ads and fix ieframe.dll error

After skype started to throw the following exception when run, it was obvious ads were the cause of the problem. This is just absurd – introduce a program crashing ad functonality – shame on you, Microsoft!

The error message indicates, that ieframe.dll is being used, so it was obvious that Internet Explorer is being called, from within Skype. So, to block skype from displaying anything inside an IE iframe it is necessary to block internet access from IE itself.
If you use IE browser on a daily basis, this method is not suitable for you.

So, to stop IE from working (and displaying Skype ads):

  • Go to Control Panel -> internet Options -> Connections -> LAN Settings
  • Untick “Automatically detect settings” box, tick “Use a proxy server for your LAN” and add a fake IP, like 127.0.0.1
  • To (temporarily) allow access for IE – untick the “Use a proxy server for your LAN” box.

    NB! Google Chrome and newer Opera browsers use the same Internet Connection settings as IE. To make them work, just add –proxy-server command line switch to its chortcut:

    Example (works as well on Opera 15+ ):

    Enjoy your ad free Skype! (until Microsoft changes the way ads are displayed)

    Essential MySQL server performance tuning

    Most important MySQL server configuration options to improve performance on new server installation:

    1. innodb_buffer_pool_size – Amount of memory MySQL will use for data cache.
    Set to ~80% of server RAM. (If server is dedicated for DB). Example for server with 32GB RAM:
    [code]
    innodb_buffer_pool_size=24G
    [/code]

    2. innodb_flush_log_at_trx_commit = 2 – log writes will happen once per second instead of every commit. Major I/O bottleneck with many writes.
    [code]
    innodb_flush_log_at_trx_commit = 2
    [/code]

    3. innodb_log_file_size – The larger the value, the less checkpoint flush activity is needed in the buffer pool, saving disk I/O.
    [code]
    innodb_log_file_size = 512M
    [/code]
    After changing the value, gracefully shutdown MySQL and move /var/lib/mysql/ib_logfile* somewhere safe just in case. If MySQL starts successfully, delete moved files.

    4. innodb_log_buffer_size – enables large transactions to run without writing the log to disk before the transactions commit, again – saving disk I/O. Default = 1MB.
    [code]
    innodb_log_buffer_size = 8M
    [/code]

    5. innodb_file_per_table – Not a performance setting, however a very important parameter to set right after server installation as it will be hard to change it later.

    In file-per-table mode, each newly created table will have its own data file, that will allow to reclaim used space after table deletion, and have other advantages

    Summary:

    [code]
    innodb_buffer_pool_size=24G
    innodb_flush_log_at_trx_commit = 2
    innodb_log_file_size = 512M
    innodb_log_buffer_size = 8M
    innodb_file_per_table
    [/code]