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
Related
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.
I am trying to create an autocomplete script for scp.
The script reads the user and hostname from my .ssh/config file
My .ssh/config file looks like:
Host host1
HostName host1
User userA
port 22
Host host2
HostName host2
User userB
port 22
Host host3
HostName host3
User userB
port 22
My .autocomplete_scp.sh file is:
# SSH
function _scp_completion() {
pcregrep -o -M 'HostName [a-zA-Z.]+[\n\t\s]+User [a-zA-Z]+'
$HOME/.ssh/config | awk 'NR % 2 == 1 { o=$2 ; next } { print $2"#"o}'
}
complete -W "$(_scp_completion)" scp
I source this file in my bashrc.
Now when I type userA and press Tab, the autocomplete function will give me userA#host1. When I type userB and hit Tab, the autocomplete function will give me userB#, but I am not able to get the full string (userB#host2 or userB#host3).
It also doesn't work when I type userA#h and hit the Tab button twice. So it seems to get stuck due to the # sign.
(When I remove the # sign from the _scp_completion function it works fine.)
Any ideas to fix this? Thanks!
The easy way to make it work is to remove '#' from $COMP_WORDBREAKS or Bash would handle # by itself. You can try like this:
COMP_WORDBREAKS=${COMP_WORDBREAKS//#}
complete -W 'userA#host1 userB#host2 userB#host3' scp
According to bash doc:
COMP_WORDBREAKS
The set of characters that the readline library treats as word separators when performing word completion.
I'm going to try to describe my problem and my end goal as best as I can, here it goes:
I have a script that fetches AWS ELB information (elb name + ports that's associated with a specific certifican arn).
So, in the end I have a text file (I call it elb_ports) and it looks something like this:
ccds-lb 636
cf-router 443 4443
dev-cf-router 443 4443
eng-jenkins-monit 443
gitlab-lb 443
gitlab-mattermost-elb 443
jenkins-np-elb 443
saml 443
uaa 443
I have another script that comes after that which I want it to go through that elb_ports file and replace the certificates with a new one, but according to Amazon's documentation: It says in order to replace the certificates, I need two things from that elb_ports file. The load balancer name and the load balancer port.
So basically their command looks like this
aws elb set-load-balancer-listener-ssl-certificate \
--load-balancer-name my-load-balancer \
--load-balancer-port 443 \
--ssl-certificate-id arn:aws:iam::123456789012:server-certificate/my-new-certificate
I want to be able to loop through the file and execute the command above to each elb and port, but my problem is with the elbs that has multiple ports associated with the cert like: cf-router 443 4443 for example.
So my idea was to split that into two lines, so like this:
cf-router 443
cf-router 4443
But I'm not sure how to add cf-router (for example) to the ports that come after the first one (there could be more than two ports using the same cert).
I hope I was able to explain my problem and end goal clearly, if this isn't a good method, I'm open to suggestions also.
EDIT: Perhaps something like this is beneficial, but not sure how to tailor it to my needs.. Like put each line in an array and the space as a delimiter and then loop through each line putting arr(1) (load balancer name) and then the load balancer port, but not sure how to count and go through >arr(2) in bash.
To split out your extra columns into separate lines:
while read -r lb_name lb_ports_str; do ## split line into lb name and port list string
read -r -a lb_ports <<<"$lb_ports_str" ## split out port list string into an array
for port in "${lb_ports[#]}"; do ## iterate through that array
printf '%s %s\n' "$lb_name" "$port" ## handle each port separately
done
done <elb_ports ## reading lines from elb_ports
Of course, that printf could be any other line referring to $lb_name and $port -- meaning you could potentially run your code that's installing new certificates here.
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
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