4번독수리의 둥지

http://networkengineering.stackexchange.com/a/23000 This has to do with how (UTP) Ethernet cabling works. In the old days, end point devices (like your PC) would use wires 1 and 2 to transmit data, and wires 3 and 6 to listen (https://en.wikipedia.org/wiki/File:Ethernet_MDI_crossover.svg) (*). The switch on the other side of the cable would listen on wires 1 and 2, and transmit on 3 and 6. Now i..

1. [root]# yum install firewalld 2. [root]# service firewalld start 3. Block SSH except specific IP address [root]# firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT 0 -s 111.111.111.111 -p tcp -m tcp --dport 22 -j ACCEPT [root]# firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT 1 -p tcp -m tcp --dport 22 -j REJECT --reject-with icmp-port-unreachable * Find out all acti..

http://unix.stackexchange.com/questions/8656/usr-bin-vs-usr-local-bin-on-linux /bin (and /sbin) were intended for programs that needed to be on a small / partition before the larger /usr, etc. partitions were mounted. These days, it mostly serves as a standard location for key programs like /bin/sh, although the original intent may still be relevant for e.g. installations on small embedded devic..

http://stackoverflow.com/questions/448023/what-is-the-difference-between-left-right-outer-and-inner-joins

// pseudo database table$contents = range(1, 255);rsort($contents);//print_r($contents); $now = $_GET['now'];if (!$now) { $now = 1;} // pseudo pagination object$p = array();$p['types'] = array('simple', 'centered');// set pagination config$p['size'] = 7;$p['psize'] = 5;$p['type'] = 'simple';// pagination preset info$p['now'] = $now;$p['total'] = count($contents);// generate pagination info$p['pt..