Sometimes system troble occur by the disk space problem. we can check root cause by some command. Volume usage per partition Most used disk directory Under / Under /var/ Check journal file size Check size and delte files which are before 3 days

confirm authentication SELECT user, host, plugin FROM mysql.user;

cp /usr/share/zoneinfo/Asia/Tokyo /etc/localtime

check memory #free -t -htotal used free shared buff/cache availableMem: 983M 488M 121M 524K 373M 341MSwap: 0B 0B 0BTotal: 983M 488M 121M ・make 1GM swap files #dd if=/dev/zero of=/var/swap bs=1M count=1024#mkswap /var/swap#swapon /var/swap

root user is able to change root user password. sudo passwd root

yum command is easy to install software in your host. yum list installed Output all installed software yum update [softwarename] ex: yum update httpd it is able to update software by this command. yum list you can know the software which is able to install.

Subnet /n Subnet IP Count /32 255.255.255.255 1 /31 255.255.255.254 2 /30 255.255.255.252 4 /29 255.255.255.248 8 /28 255.255.255.240 16 /27 255.255.255.224 32 /26 255.255.255.192 64 /25 255.255.255.128 128 /24 255.255.255.0 256 /23 255.255.254.0 512 /22 255.255.252.0 1024 /21 255.255.248.0 2048 Subnet IPs The subnet mask is used to define the range of the network.
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compress tar.gz tar -zcvf xxx.tar.gz directory decompression tar.gz tar -zxvf xxxx.tar.gz

Port Number Protocol Description 7 echo echo 53 domain Domain name protocol 123 ntp Network time protocol 137 netbios NetBIOS name server protocol 138 netbios NetBIOS datagram 139 netbios NetBIOS session 161 snmp SNMP 162 snmp SNMP trap

Port Number Protocol Description 20 ftp FTP – Data Transfer Port 21 ftp FTP – Control Port 22 ssh Secure Shell (SSH) Remote Protocol 23 telnet Telnet 25 smtp Simple Mail Transfer Protocol 53 domain Domain Name Protocol 80 http Hypertxt Transfer Protocol 110 pop3 Post Office Protocol 123 ntp Network Time Protocol 143 imap
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