I'm wondering how I can change the displaying name when I log into my server.
So for example I SSH into the server and it display my username # ec2 instance ip.
example: username#ip-10.0.0.129
what I want: username#production
I don't want it to affect any DNS, host, hostname or Ip stuff only to give it a nickname, any suggestions?
another example: When Cron finishes its job it sends an email from root
Cron <root#ip-10-0-0-129>.....
what I want: Cron <root#production>.....
My ec2 instance on aws is called production so could I somehow instead tell the system to use that name instead of the ip address?
Thanks!
You just need to customize your bash prompt settings in your ~/.bashrc file and change the value of the PS1 variable that controls the presentation of the bash prompt. There are many examples of how to do this online but here is one.
If you want to hardcode it to your username#production, you can do something like this:
PS1='\u#production: '
You can test this first right from your bash prompt before editing the bashrc file, i.e. just enter what I have above, so something like this:
DEFAULT=$PS1 #save your existing setting
PS1='\u#production: ' #try a new setting
PS1=$DEFAULT #restore the original setting
You can also just edit the hostname of your system as detailed in the AWS documentation here.
Related
I was provided a tool to do a SSH to a remote host. The remote host is a new docker to be created. I was trying to understand if there are commands being executed right after the SSH (i.e. probably using ssh -t <some commands>).
It seems like the .bash_history does not include those cmds. In such case, what else can I do to figure out what cmds being executed right after my login? Thank you.
To find out the actual commands that are executed, you could add "set -v" or "set -x" to the shell initialization file(s) on the system you are ssh-ing to.
See man bash (the "INVOCATION" section) to find out which files will executed so that you can figure out which file to add the "set" command to.
You will probably want to do that temporarily ... because the output is verbose.
Another approach would be to configure sshd to set the logging level to DEBUG and see what commands are requested. However, note that sshd DEBUG logging is a user privacy violation.
If you are trying to do this kind of stuff to find out what is happening on the first "boot" of a docker instance, try putting the (temporarily) config changes into the docker image that you are starting.
The bash history only contains command lines that are submitted to the shell via a shell command prompt.
So I am aware one can edit bash tab completion scripts with functions for a variety of behaviors
I have configured a long list of aws hosts on my .ssh/config, written as dot sepparated names, like so:
Host aws.<stack_name>.<instance_name>
HostName X.X.X.X
by default ssh bash completion scripts display the full list of hosts declared in the config file, and this is pretty good already. But I would like to add to this behavior, which currently displays the list like so:
$ ssh aws.[tab][tab]
aws.stack1.inst1 aws.stack2.inst1
aws.stack1.inst2 aws.stack2.inst2
aws.stack1.inst3 aws.stack3.inst1
aws.stack1.inst4 aws.stack4.inst1
so that I can do the following:
$ ssh aws.[tab][tab]
stack1 stack2 stack3
$ ssh aws.stack1.[tab][tab]
inst1 inst2 inst3 inst4
But I have not been able to figure out how, and where, to add this functionality by navigating through available bash_completion scripts.
I don't want to overwrite the current ssh completion, just extend its behavior when ssh is followed by aws
How/Where can/should I implement this behavior?
I'm wondering how I would go about creating my own bash script to ssh to a server. I know it's lazy, but I would ideally want not to have to type out:
ssh username#server
And just have my own two letter command instead (i.e. no file extension, and executable from any directory).
Any help would be much appreciated. If it helps with specifying file paths etc, I am using Mac OS X.
You can set configs for ssh in file ~/.ssh/config:
Host dev
HostName mydom.example.com
User myname
Then, just type
$> ssh dev
And you're done. Also, you can add your public key to the file ~/.ssh/authorized_keys so you won't get prompted for your password every time you want to connect via ssh.
Use an alias.
For example: alias sv='ssh user#hostname', then you can simply type sv.
Be sure to put a copy of the aliases in your profile, otherwise they will disappear at the end of your session.
you could create an alias like this:
alias ss="ssh username#server" and write it into your .bash_profile. ".bash_profile" is a hidden file is located in your home directory. If .bash_profile doesn't exist yet (check by typing ls -a in your home directory), you can create it yourself.
The bash_profile file will be read and executed every time you open a new shell.
You can use ssh-argv0 to avoid typing ssh.
To do this, you need to create a link to ssh-argv0 with the name of the host you want to connect, including the user if needed. Then you can execute that link, and ssh will connect you to the host of the link name.
Example
Setup the link:
ln -s /usr/bin/ssh-argv0 ~/bin/my-server
/usr/bin/ssh-argv0 is the path of ssh-argv0 on my system, yours could be different, check with which ssh-argv0
I have put it in ~/bin/ to be able to execute it from any directory (in OS X you may need to add ~/bin/ manually to your path on .bash_profile)
my-server is the name of my server, and if needed to set the user, it would be user#my-server
Execute it:
my-server
Even more
You can also combine this with mogeb answer to configure your server connection, so that you can call it with a shorter name, and avoid to include the user even if it is different than on the local system.
Host serv
HostName my-server
User my-user
Port 22
then set a link to ssh-argv0 with the name serv, and connect to it with
serv
My current solution for editing files on a remote web server is to use Fetch to browse the remote machine and TextWrangler to make the edits. But since I'm getting more comfortable navigating the command line on the remote machine (but not comfortable enough to use VIM...), I'd like to be able to type something like 'open filename.txt' on the remote machine and have TextWrangler open up on my local machine. I've heard the term "reverse tunneling" tossed around as an option, but I have no idea what to do next. Any suggestions are greatly appreciated - thanks!
Personally, I use Cyberduck as my S/FTP browser. In Cyberduck's preferences, you can define a default text editor to edit remote files. Now I can just hit Cmd+K when I have a file selected, and it will open up in TextWrangler. Whenever I save, the changes are automatically transferred to the remote file.
I was actually looking to do the same thing, and no one had written it up, so I figured this out today.
There's 2 required and 3 optional parts to this:
Enable ssh login on both computers (required)
Set up an ssh tunnel from the remote machine to your machine (required)
Set up an alias for the ssh tunnel (optional)
Set up an alias for TextWrangler on the remote machine (optional)
Set up ssh keys so you don't have to enter your password every time (optional)
You need to be able to ssh from local to remote to run the commands, and you need to be able to ssh from remote to local so it can send commands to TextWrangler.
To set up the ssh tunnel, you need to run a command on your local machine like:
ssh -f -N -R 10022:localhost:22 [username on remote machine]#[remote machine hostname]
The -f and -N flags put ssh into the background and leave you on your machine. The -R flag binds a port on the remote computer to a port on your local computer. Anything contacting the remote machine on port 10022 will be sent to port 22 on your local computer. The remote port can be anything you want, but you should choose a port > 1024 to avoid conflicts and so you don't have to be root. I chose 10022 because it's similar to ssh's default port of 22. Replace the brackets with your username and machine name.
You'll need to run that once after you log in. To make the command easier on yourself, you can add an alias in your bash profile. Add the following to your local ~/.bash_profile:
alias open-tunnel='ssh -f -N -R 10022:localhost:22 [username on remote machine]#[remote machine hostname]'
Of course, you can choose whatever alias name you like.
Once you've set up the tunnel, you can use a command like this on the remote machine:
ssh -p 10022 [username on local machine]#localhost "edit sftp://[username on remote machine]#[remote machine hostname]//absolute/path/to/file.txt"
The -p flag says to use port 10022 (or whichever port you chose earlier). This will cause the remote machine to connect to your local machine and execute the command in the double quotes without opening an interactive ssh session. The command in the quotes is the command you would run on your local machine to open the remote file in TextWrangler.
To make the command easier on yourself, you can add a function in your bash profile. Add the following to your remote ~/.bash_profile:
function edit { if [[ ${1:0:1} = "/" ]]; then abs_path="$1"; else abs_path="`pwd`/$1"; fi; ssh -p 10022 [username on local machine]#localhost "edit sftp://[username on remote machine]#[remote machine hostname]/$abs_path"; }
This is assuming that you don't have the TextWrangler command line tools installed on the remote machine. If you do, you should name the function something other than edit. For example, tw. Here, ${1:0:1} looks at the first character of the first parameter of the function, which should be the file path. If it doesn't begin with /, we figure out the absolute path by adding the current working directory (pwd) to the beginning. Now, if you're on the remote machine in /home/jdoe/some/directory/ and you run edit some/other/directory/file.txt, the following will be executed on your local machine:
edit sftp://[username on remote machine]#[remote machine hostname]//home/jdoe/some/directory/some/other/directory/file.txt
Lastly, you should set up ssh keys in both directions so you're not prompted for a password every single time. Here's a guide someone else wrote: http://pkeck.myweb.uga.edu/ssh/
I dont think this will allow opening from the command-line, but
Eclipse with Remote-System-Explorer also supports editing of files via ssh connection
I think what you're referring to is called "X11 forwarding" over ssh. Take a look at the ssh_config(5) manpage for configuration (or just use 'ssh' with the '-X' parameter). As far as i know, this does only work with X11 programs (gvim, xemacs, etc.), because the editor is actually running on the host you're connecting to - only the display stuff happens on your local machine. So TextWrangler is not an option, because it's not an X11 program.
I use Interarchy (from nolobe) for remote editing. It's a fairly advanced ftp/sftp client that gives you a finder-style view of your remote files and allows you to use your favourite editor to work on those files.
If you don't like to pay for such a program, there's an Open-Source program called "Fugu" available from the Univerity of Michigan which you can also use.
FileZilla offers this functionality as well. You can download it here. Once you've connected to your sftp you can right-click on the text file and open it with the text editor of your choice.
Minimal answer
You can use Applescript. So from the command line execute this:
osascript <<EOF
tell application "TextWrangler"
activate
open location {"sftp://myusername:#my.server:22222//home/username/.bashrc"}
end tell
EOF
Notes
Obviously you wouldn't want to type a here document on every invocation, so my suggestion would be to put this logic inside a regular shell script:
osascript <<EOF
tell application "TextWrangler"
activate
open location {"$1"}
end tell
EOF
Then invoke the script like this:
sh ~/bin/textwrangler.sh "sftp://myusername:#my.server:22222//home/username/.bashrc"
Specifying a host-qualified path can get tedious each time so either hardcode that in your script, or bind the script invocation to a keystroke via your shell. For bash:
bind '"\et":"sh ~/bin/textwrangler.sh \"sftp://myusername:#my.server:22222/\""'
Now you generate the majority of the command by pressing Alt-t
I'm running a couple of standard Fedora instances on EC2. I feel the public hostnames of the instances assigned by Amazon are too weird and hard to remember. I'd like to change them to something short (like red/blue/green/etc).
Is there any draw back in doing this? And how do I set it up such that it persists after reboots?
Thanks.
Before you get started, try running hostname and hostname --fqdn and take note of what the responses are.
You can edit /etc/hostname and set a hostname, which will stick around after rebooting. You can force the hostname to be "reloaded" by using hostname -F /etc/hostname to read that value into the hostname. The bash prompt will change after you logout and login.
warning / note:
Yes, it is nice to have the hostname in the bash prompt set to something more useful than ip-123-123-123-123 but I've decided to leave mine (at least for now) because it seems like a lot of things really count on having the hostname on ec2 instances set in a standard way. After editing /etc/hostname and changing the hostname to webserver a lot of the services seems to fail because the hostname would not resolve, and apache wouldn't start. Next I edited /etc/hosts and added in
127.0.0.1 webserver
as the second line. Apache would then start but complained that it couldn't find the FQDN. I confirmed that running hostname --fqdn no longer worked.
Next I consulted man hostname and learned that while you can set the hostname it appears that the FQDN is what is returned via a DNS lookup.
THE FQDN
You can't change the FQDN (as returned by hostname --fqdn) or the DNS domain name (as returned by dnsdomainname) with this command. The FQDN of the system is the name that the resolver(3) returns for the host name.
Technically: The FQDN is the name getaddrinfo(3) returns for the host name returned by gethostname(2). The DNS domain name is the part after the first dot.
Therefore it depends on the configuration (usually in /etc/host.conf) how you can change it. Usually (if the hosts file is parsed before DNS or NIS) you can change it in /etc/hosts.
I think it might be possible to set the system / fool the system into return the FQDN, something like ip-123-123-123-123.ec2.internal even though the hostname is webserver but at this point it started to seem like more trouble than it was worth, and that for me to have a nicer bash prompt might cause a lot software and configuration problems down the road and so I decided to give up.
I also learned that a lot of amazon ec2 instances use something called cloud-init:
cloud-init is the Ubuntu package that handles early initialization of a cloud instance. It is installed in the Ubuntu Cloud Images and also in the official Ubuntu images available on EC2.
Some of the things it configures are:
setting a default locale
setting hostname
generate ssh private keys
adding ssh keys to user's .ssh/authorized_keys so they can log in
setting up ephemeral mount points
cloud-init's behavior can be configured via user-data. User-data can be given by the user at instance launch time. This is done via the --user-data or --user-data-file argument to ec2-run-instances
I also found this which talks about how the hostname is configured with cloud-init:
On EBS instances, a shutdown and later start would end up with a different IP address.
In the case where the user has not modified /etc/hostname from its original value (seeded by metadata's 'local-hostname'), then cloud-init will again set the hostname and update /etc/hostname.
In the case where the user has modified /etc/hostname, it will remain user managed.
Additionally, if /etc/cloud/cloud.cfg contains 'preserve_hostname' value set to a True value, then /etc/hostname will not ever be touched.
The interesting takeaway is that if you don't change the hostname the cloud-init package will keep it up to date for you.
If someone else has a workaround or can address some of the issues mentioned and help reassure that nothing will break on ec2 instances because of changing the hostname I would be happy to hear it.
Another way is to simply edit ~/.bashrc and prepend PS1 with the nickname of the machine.
Edit: perhaps more correctly, machine-wide, e.g. on the AWS Linux AMI (an example) (paste this into console or add to your arbitrary install .sh):
cat << EOF | sudo tee /etc/profile.d/ps1.sh
if [ "$PS1" ]; then
PS1="[\u#myinst1:\l \t \! \W]\\$ "
fi
EOF
Edit /etc/sysconfig/network as root.
Replace
HOSTNAME=localhost.localdomain
with
HOSTNAME=hostname.DOMAIN_NAME
Then, either reboot or run /etc/init.d/network restart
The server then should report its name as a FQDN.
From this site:
Change the hostname on a running system
On any Linux system you can change its hostname with the command hostname (surprised?)…
Here are some quick usages of the command line hostname:
$> hostname
without any parameter it will output the current hostname of the system.
$> hostname --fqd
it will output the fully qualified domain name (or FQDN) of the system.
$> hostname NEW_NAME
will set the hostname of the system to NEW_NAME.
You can also edit /etc/hostname (at least on Ubuntu).
To make sure it stays after a reboot in AWS, either add the command in /etc/rc.local so it runs when the machine starts.
There's also a way to set the hostname dynamically via USER_DATA:
USER_DATA=`/usr/bin/curl -s http://169.254.169.254/latest/user-data`
HOSTNAME=`echo $USER_DATA`
IPV4=`/usr/bin/curl -s http://169.254.169.254/latest/meta-data/public-ipv4`
hostname $HOSTNAME
echo $HOSTNAME > /etc/hostname
To change the system hostname to a public DNS name
Follow this procedure if you already have a public DNS name registered
Open the /etc/sysconfig/network configuration file in your favorite text editor and change the HOSTNAME entry to reflect the fully qualified domain name (such as webserver.mydomain.com).
HOSTNAME=webserver.mydomain.com
Reboot the instance to pick up the new hostname.
[ec2-user ~]$ sudo reboot
Log into your instance and verify that the hostname has been updated. Your prompt should show the new hostname (up to the first ".") and the hostname command should show the fully qualified domain name.
[ec2-user#webserver ~]$ hostname
webserver.mydomain.com
To change the system hostname without a public DNS name
Open the /etc/sysconfig/network configuration file in your favorite text editor and change the HOSTNAME entry to reflect the desired system hostname (such as webserver).
HOSTNAME=webserver.localdomain
Open the /etc/hosts file in your favorite text editor and add an entry beginning with 127.0.1.1 (on DHCP systems) or eth0's address (on static IP systems) to match the example below, substituting your own hostname. (127.0.0.1 should be left as the localhost line.)
127.0.0.1 localhost localhost.localdomain
127.0.1.1 webserver.example.com webserver
Reboot the instance to pick up the new hostname.
[ec2-user ~]$ sudo reboot
Log into your instance and verify that the hostname has been updated. Your prompt should show the new hostname (up to the first ".") and the hostname command should show the fully qualified domain name.
[ec2-user#webserver ~]$ hostname
webserver.localdomain
Note: You can also change the shell prompt without affecting the hostname. Refer to this AWS documentation.
Sure, you can do that if you have your own domain (setup a CNAME to point to the Amazon hostname). Otherwise, you're pretty much stuck with the one they give you (or an Elastic IP, if you set one of those up).
The /etc/rc.local solution worked for me for a basic hostname but does not give me a FQDN.
In my Linux AMI (a snapshot of other instance).. none of the above formula worked. Then, I simply changed HOSTNAME field in file: /etc/init.d/modifyhostname and did a normal reboot.
You will need to do multiple things to set the hostname:
hostname newname - sets the hostname, but is volatile
edit /etc/hostname - sets the hostname for the next reboot
edit /etc/hosts - to keep sudo from complaining
I put these together into a script and uploaded it as a gist:
https://gist.github.com/mnebuerquo/5443532036af8b48995547e2817dba85
sudo hostname *yourdesiredhostnamehere*
sudo /etc/init.d/networking restart
then the hostname is changed. On my server all other services like apache and postfix works. Server is Ubuntu 12.04 LTS