After adding a hosting file using etc/hosts on Mac OS X machines manually we found out we needed to remove the current hosts and add a new one. I'm wondering if it's possible to add a hosting file for Mac OS X using Bash.
This is the current state. How do we change the final line or add one to it?
##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
##
127.0.0.1 localhost Computer_Name
255.255.255.0 broadcasthost
::1 localhost
10.24.82.5 server_name
I guess you are asking how to edit the file from the command line, then
$ sed -i.OLD 's#10\.24\.82\.5 #8.8.8.8 #' /etc/hosts
The -i option allows sed to edit in-place.
You may need sudo to have write permission to that file.
You can simply use sed to change it, you just need to provide new ip address:
sed 's/^.*\(server_name\)/new_ip_address \1/' file
Related
I had no issues with accessing my apps running in Ubuntu through WSL from windows until I installed docker and did a reboot.
I checked my hosts configuration file and it looked something like the following:
# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
# Added by Docker Desktop
192.168.1.244 host.docker.internal
192.168.1.244 gateway.docker.internal
# To allow the same kube context to work on the host and the container:
127.0.0.1 kubernetes.docker.internal
# End of section
I commented out the second to last line
# 127.0.0.1 kubernetes.docker.internal
and flushed my dns using
ipconfig /flushdns
but still if I try to access my node app running on port 3001 in wsl my browser gives the "Can't reach this page message"
This isn't an issue with node or my app because I am able to successfully curl my app from the ubuntu terminal
I was able to fix the issue by simply adding the ip address for wsl to my hosts file above the docker declaration:
<ip address of wsl> localhost
I am wanting to modify my ~/.ssh/config file so that it reads IP address from a text file. For example:
Host prod-app
HostName ip-address-here
User root
Port 22
IdentityFile ~/.ssh/my-key
Since my EC2 instances have different public IP addresses after deployments, I am trying to figure out a way that I can just simply have this read from a text file. So rather than above, it would look something like this:
Host prod-app
HostName $(cat $HOME/Documents/app_prod.txt)
User root
Port 22
IdentityFile ~/.ssh/my-key
That doesn't work because of the following error:
/Users/nutella/.ssh/config line 33: garbage at end of line; "$HOME/Documents/app_prod.txt)"
Is there an easy way to get this work or a better way by chance?
You could use an include statement:
Host prod-app
include ~/Documents/app_prod.txt
User root
Port 22
IdentityFile ~/.ssh/my-key
app_prod.txt:
HostName 192.0.2.1
I have to run some servers with different names. So I changed the hostname in Windows 10 inside C:\Windows\System32\drivers\etc\hosts. I changed the name from localhost to brandcil.local:
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 brandcil.local
# ::1 brandcil.local
Now when I am running nslookup 127.0.0.1 in powershell terminal, it is showing this:
Server: UnKnown
Address: 192.168.43.1
Name: localhost
Address: 127.0.0.1
I restarted my machine but it does not take effect. How do I change the hostname then?
Changing the hosts file will not change the hostname. It is only used for hostname-IP-resolution. Besides that, each line that begins with # is a comment and not an active configuration. You can rename a computer with the following PowerShell cmdlet:
Rename-Computer -NewName brandcil -Restart
First of all, any line in the hosts file that begins with # is a comment and will be ignored. The file itself tells you this if you read it. Second, the hosts file has nothing to do with your computer's hostname. All you're doing is creating aliases that will only work on the machines you modify the hosts file on. You're not changing the hostname at all. Third, localhost -> 127.0.0.1 is a static mapping no longer controlled by the hosts file so it will always map to 127.0.0.1. Again, the hosts file tells you this if you read it.
To rename your computer go into Settings --> System --> About. There's a "Rename this PC" button.
If you don't want to use that, then I recommend using the Rename-Computer Powershell command.
Wanting to set hostname and domain name or wanting so take control of what dns server to use.
If I edit resolv.conf at reboot changes are reseted to what comes from dhcp
playing with /etc/cloud/cloud.cfg doesn't seem to change the problem.
It's because it's got nothing to do with cloud settings lol
the magie manly happens in /etc/dhcp/dhclient.conf
I commented out that line
send host-name = gethostname();
request subnet-mask, broadcast-address, time-offset, routers,
# domain-name, domain-name-servers, domain-search, host-name,
dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
netbios-name-servers, netbios-scope, interface-mtu,
rfc3442-classless-static-routes, ntp-servers;
Then in /etc/cloud/cloud.cfg I had to adjust a couple things
[...]
# preserve_hostname: false
preserve_hostname: true
[...]
# - timezone
[...]
# manage_etc_hosts: true
manage_etc_hosts: false
I also needed to add a line in /etc/hosts
127.0.1.1 myName.Mydomain.foo myName
127.0.1.1 xxxxx.your-cloud.etc xxxxx
127.0.0.1 localhost
Lost time on this... so I thought it might be nice to share the solution.
I have private DNS servers and I want to write them to resolv.conf with resolvconf on Debian on AWS/EC2.
There is a problem in the order of nameserver entries.
In my resolv.conf, EC2's default nameserver is always written at first line like so:
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 172.16.0.23
nameserver 10.0.1.185
nameserver 10.100.0.130
search ap-northeast-1.compute.internal
172.16.0.23 is EC2's default nameserver and others are mine.
How to remove EC2 entry? Or, how to move EC2 entry to third?
Here I have an interface file:
% ls -l /etc/resolvconf/run/interface/
-rw-r--r-- 1 root root 62 Jun 7 23:35 eth0
It seems that the file eth0 is automatically generated by dhcp so can't remove it permanently.
% cat /etc/resolvconf/run/interface/eth0
search ap-northeast-1.compute.internal
nameserver 172.16.0.23
My private DNS entry is here:
% cat /etc/resolvconf/resolv.conf.d/base
nameserver 10.0.1.185
nameserver 10.100.0.130
Please help.
I think I just solved a very similar problem. I was bothered by Amazon EC2's crappy internal DNS servers so I wanted to run a local caching dnsmasq daemon and use that in /etc/resolv.conf. At first I just did echo nameserver 127.0.0.1 > /etc/resolv.conf but then I realized that my change would eventually be overwritten by the DHCP client after a reboot or DHCP lease refresh.
What I've now done instead is to edit /etc/dhcp3/dhclient.conf and uncomment the line prepend domain-name-servers 127.0.0.1;. You should be able to use the prepend directive in a very similar way.
Update: These instructions are based on Ubuntu Linux but I imagine the general concept applies on other systems as well, even other DHCP clients must have similar configuration options.
I'm approaching this problem from the other direction (wanting the internal nameservers), much of what I've learned may be of interest.
There are several options to control name resolution in the VPC management console.
VPC -> DHCP option sets -> Create dhcp option set
You can specify your own name servers there.
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_DHCP_Options.html
Be sure to attach this dhcp option set to your VPC to get it to take effect.
Alternatively (I found this out by mistake) local dns servers are not set if the following settings are disabled in VPC settings:
DnsHostnames
and
DnsSupport
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-dns.html
Settings can also be overridden locally (which you'll notice if you move instances between vpcs). /etc/dhcp/dhclient.conf
The following line might be of interest:
prepend domain-name-servers
Changes, of course, take effect on dhclient start.
How do I assign a static DNS server to a private Amazon EC2 instance running Ubuntu, RHEL, or Amazon Linux?
Short Description
Default behavior for an EC2 instance associated with a virtual private cloud (VPC) is to request a DNS server address at startup using the Dynamic Host Configuration Protocol (DHCP). The VPC responds to DHCP requests with the address of an internal DNS server. The DNS server addresses returned in the DHCP response are written to the local /etc/resolv.conf file and are used for DNS name resolution requests. Any manual modifications to the resolv.conf file are overwritten when the instance is restarted.
Resolution
To configure an EC2 instance running Linux to use static DNS server entries, use a text editor such as vim to edit the file /etc/dhcp/dhclient.conf and add the following line to the end of the file:
supersede domain-name-servers xxx.xxx.xxx.xxx, xxx.xxx.xxx.xxx;
Ubuntu - dhclient.conf - DHCP client configuration file
The supersede statement
supersede [ option declaration ] ;
If for some option the client should always use a locally-configured value or values
rather than whatever is supplied by the server, these values can be defined in the
supersede statement.
The prepend statement
prepend [ option declaration ] ;
If for some set of options the client should use a value you supply, and then use the
values supplied by the server, if any, these values can be defined in the prepend
statement. The prepend statement can only be used for options which allow more than one
value to be given. This restriction is not enforced - if you ignore it, the behaviour
will be unpredictable.
The append statement
append [ option declaration ] ;
If for some set of options the client should first use the values supplied by the server,
if any, and then use values you supply, these values can be defined in the append
statement. The append statement can only be used for options which allow more than one
value to be given. This restriction is not enforced - if you ignore it, the behaviour
will be unpredictable.
In here someone come with solution that basically replaces the file on boot using rc.local
https://forums.aws.amazon.com/thread.jspa?threadID=74497
Edit /etc/sysconfig/network-scripts/ifcfg-eth0 to say PEERDNS=no
Create a file called /etc/resolv.backup with what you want
Add the following 2 lines to /etc/rc.local:
rm -f /etc/resolv.conf cp /etc/resolv.backup /etc/resolv.conf
This is what we are doing for our servers in the environment.
interface "eth0"
{
prepend domain-name-servers 10.x.x.x;
supersede host-name "{Hostname}";
append domain-search "domain";
supersede domain-name "DOMAIN";
}
Hope this helps.
The following worked in a Debian stretch on AWS EC2.
Just create /etc/dhcp/dhclient-enter-hooks.d/nodnsupdate:
#!/bin/sh
make_resolv_conf(){
:
}
Then you can modify /etc/resolv.conf and it will persist your changes across restarts.
Setup in crontab as
#reboot cp -r /home/.../resolv.conf /etc/resolv.conf