I want, when my centos 7 server boots, to run
echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse
because I want to reuse open connections.
Systemd is allready installed, but my command is not a service, just a one time execution command at startup.
How can I run automatically this command at startup ? Thanks !
Add your command to
/etc/rc.d/rc.local
and it will run at startup.
The correct way to make the changes persistent is to edit the file:
/etc/sysctl.conf
After the change, type:
sysctl -p
This will load the changes into the current session. The fact that the settings are in /etc/sysctl.conf will ensure that they load on reboots.
Related
I am using Code Server within my Cloud Shell. I need to use the port 3000 for a specific npm package. Unfortunately port 3000 is already used by the default editor Theia within Cloud Shell.
I have already tried the following:
sudo kill {{PID of Theia process}} ...but it restarts again immediatelly
searched for settings within /google/devshell/editor/theia ...but could not find any port settings
sudo netstat -tlnp gives the following output:
Any help is very appreciated.
As mentioned by JShinigami, That issue got resolved here by changing the port of the other application, other alternative of resolving this issue is as below :
First I would recommend you to reset your cloud shell.
You can refer to the Answer to follow the steps on how to kill a process running on the particular Port.
Option 1 A One-liner to kill only LISTEN on specific port:
kill -9 $(lsof -t -i:3000 -sTCP:LISTEN)`
Option 2 If you have npm installed you can also run
npx kill-port 3000
I also found this answer on stack overflow that may be relevant as it shows how they were able to kill the process once they obtained its PID.
could you run the following command :
"sudo netstat -tlnp"
From the above you will be able to tell what processes are running on the ports. From there you will see the Possibility of "auto restart" configuration somewhere causing the process to appear even after kill command.
Found this useful article on ways to list processes running on ports.
This is cloudshelledit occupy the port
If you don't need cloudshelledit and can kill off
And if you open the cloudshelledit, this process is not shut off
cloudshelledit
I need to create AWS CentOS 7 instance images for a customer, and need it to automatically send the ip and instance id to our AWS server every time the instance boots. For example, this is the very basic test version of the script I need to run:
#!/bin/bash
$serverIP=""
curl "https://$serverIP"/myphp.php?id='sentid'&ip='sentip'"
If the script is run directly, it works fine and is received by the server and processed there. But I can't get it to run at boot. I cannot put the script in the "User Data" directly due to security concerns as the customer can then see it easily, it needs to be in a script in the filesystem of the image.
I've tried several things that work fine on a physical Linux server, but not on AWS. I know profile.d runs every time someone logs in but over-sending like that is fine.
/etc/profile.d/myscript.sh
This stops the AWS instance from booting. Even just
#!/bin/bash/
echo "hello world"
prevents it from booting. The instance starts, but when you go to ssh into it you get 'Network Error: connection timed out', which is the standard error if you put a wrong ip in, or upset it by leaving a service like httpd enabled.
However, a blank bash script with just #!/bin/bash will allow the instance to start. Removing the script via user data usually makes it boot, sometimes it just dies.
The first thing I tried was crontab. I did:
crontab -e
#reboot /var/ook/myscript.sh
systemctl enable crond.service
But the instance wouldn't start. So I put "systemctl disable crond.service" in the User Data and one booted, but another still stayed dead. Myscript.sh was just another echo "doob" >> file which worked fine when run directly.
I tried putting in /etc/systemd/system/my-startup.service:
[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/var/ook/writedood.sh
[Install]
WantedBy=multi-user.target
then:
systemctl enable my-startup.service
But this did nothing. My script "writedood.sh" was just echo "doob" >> ./file.txt ensuring file.txt was chmod 777. At least it didn't prevent the instance from starting.
To give context, an instance won't start if httpd is left enabled on shutdown, but will if you disable it in User Data.
I wanted to have a go at putting something in init.d but I'm not sure how to simply tell it to run a script once in the background, and given the plethora of success I've had so far with the instance not restarting, I'm not holding out much hope that that would work.
Thanks in advance!
EDIT::: I realised that sometimes AWS EC2 Instances Console is causing the problem where I can't ssh in after stopping and starting. It blanks the public ipv4 address when I click stop, but when I start, it puts the old address up and hangs. If I refresh the page, or uncheck/check the instance; the ip changes to the new address. This has caused much consternation.
Crontab worked if I placed the scripts and output file in different folders. It's very finicky; any errors, such as it not being able to write to the output file, and the instance won't start. I put startscript.sh in /usr/local/src, and output.out to /tmp/ to ensure there were no permissions problems, and now the instance starts and runs the script on boot.
I then realised that sometimes AWS EC2 Instances Console is causing the problem where I can't ssh in after stopping and starting. It blanks the public ipv4 address when I click stop, but when I start, it puts the old address up and hangs. If I refresh the page, or uncheck/check the instance; the ip changes to the new address. This has caused much consternation.
explaining all that has been tried and double checked.
Set up on local windows machine:
Xming installed and running.
in ssh_config ForwardX11 is set to yes.
In VS code remote connection config the the Forward X11 is set to yes.
Set up on GCP compute engine with Debian / Linux 9 and 1 GPU[free tier]:
xauth is installed.
In the sshd_config file below is set:
X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost no
The sshserver has be restarted to ensure below setting are read .
from local workstation I fire gcloud compute ssh --ssh-flag="-X" tensorflow-2-vm(instance name) and the response is :
/usr/bin/xauth: file /home/user/.Xauthority does not exist,
So, I attempted to perform the below on the remote compute engine with instance name - tensorflow-2-vm and user trapti_kalra:
trapti_kalra#tensorflow-2-vm:~$ xauth list
xauth: file /home/trapti_kalra/.Xauthority does not exist
trapti_kalra#tensorflow-2-vm:~$ mv .Xauthority old.Xauthority
mv: cannot stat '.Xauthority': No such file or directory
trapti_kalra#tensorflow-2-vm:~$ touch ~/.Xauthority
trapti_kalra#tensorflow-2-vm:~$ xauth generate :0 . trusted
xauth: (argv):1: unable to open display ":0".
trapti_kalra#tensorflow-2-vm:~$ sudo xauth generate :0 . trusted
xauth: file /root/.Xauthority does not exist
xauth: (argv):1: unable to open display ":0".
so, looks like something is missing, any help will be appreciated. This was working with a EC2 server before I moved to GCP.
Create n new file: touch ~/.Xauthority
Log out and back in again with your ssh session. (I'm using MobaXterm)
Then it writes the needed.
You logged into your Linux server over ssh and got the following error;
.Xauthority does not exist
Solution :
Let's go into the /etc/ssh/sshd_config file and remove the # sign at the beginning of the 3 lines below
X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost yes
Then systemctl restart sshd
Login again and you will not get the error.
There are many solutions to this problem, it can also depend on what machine you originate from. If you come from a Linux box, enabling sshd config options like:
X11Forwarding yes
could be enough.
When you use a Macbook however the scenario is different. In that case, you need to install xQuartz with brew:
brew install xquartz
And after this start it:
xQuartz &
After this is done the xQuartz logo appears in your bar and you can right-click the icon and start the terminal from the Applications menu. After you perform this you can run the following:
echo $DISPLAY from this terminal. This should give you the output:
:0
When you have another terminal such as iTerm, you can export this value in another terminal with export DISPLAY=:0 As long as xQuartz is still running the other terminal should be able to continue to use xQuartz.
After this you can SSH into the remote machine and check if the display variable is set:
$: ssh -Y anldisr#my-remote-machine
$: echo $DISPLAY
localhost:11.0
It took me a hour to figure this out, hope it helps someone. :)
This also happened when I added a new user to remote machine without giving the user a sudo privilege during creation.
To resolve, I used the root user or a sudo privileged user to assign a sudo privilege to the new user. Exit the new user and ssh again into your server.
> $ sudo usermod -aG sudo [newUser]
Whenever an AWS autoscaling group launches new ubuntu instance and I try to install any package on that instance it gives me the following error:
[stderr]E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)
[stderr]E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend),
Is there another process using it?
I tried to find a solution and manually fixed it but I don't know why whenever the autoscaling group launches a new ubuntu instance it gives the following error.
When any command updates the Ubuntu or installs a new application, it locks the dpkg(Debian Package Manager).
To identify the problem, please look at the logs
If your system is installing some updates you may find journalctl logs journalctl -u apt-daily.service. This usually happend when the system is set to update itslef and you will notice such activity with this ps -ef | grep apt.systemd.daily and you can check these setting in the file /etc/apt/apt.conf.d/20auto-upgrades
/var/log/dpkg.log*(as it may get rotated) check these logs to find which all services were trying to get installed
Once you have identified the problem, you can solve with these methods:
If system is updating, then try to wait by executing sleep command in the --user-dataof your bootstrapping script
If your 1st installation of an service/application is blocking other one, then put a condition to wait/sleep until the first service is up and so on with rest of the services you are installing.
This was a common problem in Ubuntu 16.04 LTS as per, and you can find the same with the solution code https://forums.aws.amazon.com/thread.jspa?threadID=251663
A snippet of code from the referenced link:
until service codedeploy-agent status >/dev/null 2>&1; do
sleep 60
rm -f install
wget https://aws-codedeploy-us-west-2.s3.amazonaws.com/latest/install
chmod +x ./install
sudo ./install auto
service codedeploy-agent restart
done
SSH into the instance before/while the UserData is running and check which process has acquired the lock:
$ lsof /var/lib/dpkg/lock-frontend
Also, try to enable CodeDeploy agent at the last step after performing all other steps in UserData, like:
https://gist.github.com/say8425/8344d19911dba20fab5538b85006bd31
I have a bash script. I would like to run it continuously on google cloud server. I connected to my VM via SSH in browser but after I've closed my browser, script was stopped.
I tried to use Cloud Shell but if I restart my laptop, script launches from start. It doesn't work continuously!
Is it possible to launch my script in google cloud, shut down laptop and be sure what my script works?
The solution: GNU screen. This awesome little tool let's you run a process after you've ssh'ed into your remote server, and then detach from it - leaving it running like it would run in the foreground (not stopped in the background).
So after we've ssh'ed into our GCE VM, we will need to:
1. install GNU screen:
apt-get update
apt-get upgrade
apt-get install screen
type "screen". this will open up a new screen - kind of similar in look & feel to what "clear" would result in.
run the process (e.g.: ./init-dev.sh to fire up a ChicagoBoss erlang server)
type: Ctrl + A, and then Ctrl + D. This will detach your screen session but leave your processes running!
feel free to close the SSH terminal. whenever you feel like it, ssh back into your GCE VM, and type screen -r to resume your previously detached session.
to kill all detached screens, run:
screen -ls | grep pts | cut -d. -f1 | awk '{print $1}' | xargs kill
You have the following options:
1. Task schedules - which involves cron jobs. Check this sample. Via this answer;
2. Using startup scripts.
I performed the following test and it worked for me:
I created an instance in GCE, SSH-d into it and created the following script, myscript.bash:
#!/bin/bash
sleep 15s
echo Hello World > result.txt
and then, ran
$ bash myscript.bash
and immediately closed the browser window holding the SSH session.
I then waited for at least 15 seconds, re-engaged in an SSH connection with the VM in question and ran $ ls and voila:
myscript.bash result.txt
So the script ran even after closing the browser holding the SSH session.
Still, technically, I believe your solution lies with 1. or 2.
You can use
nohup yourscript.sh > output_log_file.log
I faced similar issue. I logged into Virtual Machine through google cloud command on my local machine, tried to exit by closing the terminal, It halted the script running in the instance.
Use command exit to log out of cloud consoles in local machine putty console (twice).
Make sure you have not enabled "PREEMPT INSTANCE" while creating a VM instance.
It will force to close the instance within 24 hours to reduce the costing by a huge difference.
I have a NodeJS project and I solved with pm2