Chromebook Secure Shell App Remove Known_hosts
Using CTRL+SHIFT+J to open Javascript console. Run the following command to clear all knownhosts.
term_.command.removeAllKnownHosts()
KVM Qemu Forward Ports with iptables
Forward rule:
sudo iptables -I FORWARD -o virbr0 -d 192.168.122.0/24 -j ACCEPT
Centos KVM Guest No Internet Access
It is strange that guest cannot access internet.
Try step 1:
sudo systemctl restart libvirtd
Mount USB Drive Automatically on Ubuntu
- Find USB UUID
sudo blkid /dev/sdb2 | awk -F'"' '{print $2}'
Postfix Monitor Sent Mails and Block Domains
Check how many mails has been sent via postfix.
If the number is to big, it must be hacked by someone on some services.
sudo grep "status=sent" /var/log/mail.log | egrep -ve 'postfix/(cleanup|pickup|master|qmgr|smtpd|local|pipe)' | wc -l
IP Reserved Loopback and Private Addresses
Range Start Address |
Range End Address |
“Classful” Address Equivalent |
Classless Address Equivalent |
Description |
|---|---|---|---|---|
0.0.0.0 |
0.255.255.255 |
Class A network 0.x.x.x |
0/8 |
Reserved. |
10.0.0.0 |
10.255.255.255 |
Class A network 10.x.x.x |
10/8 |
Class A private address block. |
127.0.0.0 |
127.255.255.255 |
Class A network 127.x.x.x |
127/8 |
Loopback address block. |
128.0.0.0 |
128.0.255.255 |
Class B network 128.0.x.x |
128.0/16 |
Reserved. |
169.254.0.0 |
169.254.255.255 |
Class B network 169.254.x.x |
169.254/16 |
Class B private address block reserved for automatic private address allocation. See the section on DHCP for details. |
172.16.0.0 |
172.31.255.255 |
16 contiguous Class B networks from 172.16.x.x through 172.31.x.x |
172.16/12 |
Class B private address blocks. |
191.255.0.0 |
191.255.255.255 |
Class B network 191.255.x.x |
191.255/16 |
Reserved. |
192.0.0.0 |
192.0.0.255 |
Class C network 192.0.0.x |
192.0.0/24 |
Reserved. |
192.168.0.0 |
192.168.255.255 |
256 contiguous Class C networks from 192.168.0.x through 192.168.255.x |
192.168/16 |
Class C private address blocks. |
223.255.255.0 |
223.255.255.255 |
Class C network 223.255.255.x |
223.255.255/24 |
Reserved. |
Linux Firewall for Docker Swarm on CentOS 7
Firewalld
firewall-cmd --add-port=2376/tcp --permanent
firewall-cmd --add-port=2377/tcp --permanent
firewall-cmd --add-port=7946/tcp --permanent
firewall-cmd --add-port=7946/udp --permanent
firewall-cmd --add-port=4789/udp --permanent
firewall-cmd --reload
systemctl restart docker
Docker ENTRYPOINT vs CMD
Both ENTRYPOINT and CMD can identify which executable should be run when a container is started from image.
Docker block oubound network traffic
Install iptables in docker and run it in entrypoint.sh. To disable iptables, run touch myenv/MAINTENANCE and restart container