Some Important CentOS Commands

Some Important CentOS Commands

### Check Selinux, Selinux is a firewall

-> getenforce

### Disable Selinux

-> vim /etc/sysconfig/selinux

### Change IP

-> nmtui

###check hidden file
->ls -ls

### read any file
-> cat filename

#Search file or folder
-> find / -name ansible

###if any partition is read only
mount -o remount, rw /

### check any html file
-> curl pagename

cd /var/www/html

###Login another computer
-> ssh root@192.168.0.136

###login another computer without password
->ssh-keygen
->cd /root/.ssh/
## id_rsa -> private key
## id_rsa.pub -> public key
### copy private key and public key to another computer
->ssh-copy-id root@192.168.0.136

### access mysql
-> mysql -u root -p

### Check mysql status
-> systemctl status mysqld
$ sudo systemctl enable mysqld
$ sudo systemctl start mysqld

### check dns of any website
–> nslookup www.google.com

### Check all ports
—> ss
cat /etc/services
grep -w 80 /etc/services
sudo lsof -i -P -n | grep LISTEN
sudo netstat -tulpn | grep LISTEN
sudo netstat -tulpn | grep :443
sudo ss -tulpn | grep LISTEN
sudo ss -tulpn | grep ‘:22’

### mysql Password reset
1. sudo grep ‘temporary password’ /var/log/mysqld.log ( a temp pass will be generated)
2. $ sudo mysql_secure_installation

### disbale DNS
1. sudo sed -i ‘s/^dns=dnsmasq/#&/’ /etc/NetworkManager/NetworkManager.conf
sudo service network-manager restart
sudo service networking restart