Lord Loh.'s questions

I am using portainer and am unable to manage remote endpoints. I tried using the command line to connect to remote docker nodes, but got a message Cannot connect to the Docker daemon at tcp://<remote_ip>:<port>. Is the docker daemon running?.

Yes, they are running. I have added myself to the docker group and can access docker by SSHing into the nodes. However I cannot access any docker nodes remotely.

I modified /etc/default to add / uncomment DOCKER_OPTS="--dns 8.8.8.8 --dns 8.8.4.4 -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock"

I also modified /etc/init.d/docker and /etc/init/docker.conf to include DOCKER_OPTS="-H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock".

I restarted the docker service, logged out and logged in multiple times in the process, but still cannot connect to the remote node. I cannot even connect to the local node by passing the IP.

What did I miss out? What configuration in what file exposes the API over TCP?

user@hostname:~$ docker -H tcp://<REMOTE_IP>:2375 info
Cannot connect to the Docker daemon at tcp://<REMOTE_IP>:2375. Is the docker daemon running?
user@hostname:~$ docker -H tcp://127.0.0.1:2375 info
Cannot connect to the Docker daemon at tcp://127.0.0.1:2375. Is the docker daemon running?
user@hostname:~$ docker -H tcp://<LOCAL_IP>:2375 info
Cannot connect to the Docker daemon at tcp://<LOCAL_IP>:2375. Is the docker daemon running?
user@hostname:~$

Edit: Running ps aux | grep -i docker returns this -

root      3581  0.1  0.2 596800 41540 ?        Ssl  04:17   0:35 /usr/bin/dockerd -H fd://
root      3588  0.0  0.0 653576 14492 ?        Ssl  04:17   0:18 docker-containerd -l unix:///var/run/docker/libcontainerd/docker-containerd.sock --metrics-interval=0 --start-timeout 2m --state-dir /var/run/docker/libcontainerd/containerd --shim docker-containerd-shim --runtime docker-runc

This script keeps outputting a 1. and I cannot understand why.

<?php
        passthru("nohup sudo rndc reload sd.example.com",$op);
        print_r($op);
?>

I have also tried the above code without the nohup. I have the following line in my sudoers file

apache ALL = NOPASSWD: /usr/sbin/rndc reload sd.example.com

Just to test, temporally, I allowed apache a shell, logged in as apache by sudo su apache and successfully managed to execute sudo rndc reload sd.example.com. I have been restarting httpd each time I made changes to the sudoers file.

I do not see any error message in my log files wither. What could I be possibly doing wrong? None of the similar threads have pointed me to anything that solved my problem or debug it.

I would like to have certain zones hosted by my DNS servers to be accessible internet-wide while restricting certain zones only to specific IP addresses (local or internet). Is this possible? How do I do it?

Putting the allow-query { <ip.v4.ad.dr>; }; option in the zone {...} did not seem to stop me from fetching A records in that zones from IP addresses other than the one specified :-(

I am running scanlogd to detect port scans. I have observed the following to generate a log message in /var/log/syslog.

• When I use zenmap (nmap gui) to port scan this system from another computer on the same subnet
• Using nmap to scan the system from the loalhost using destination as 127.0.0.1
• Using nmap to scan the system from the loalhost using the external IP as the destination.
• From my phone on a different subnet in the same organization (A University).

/var/log/syslog:

Aug 16 15:38:59 LIVE272675 scanlogd: 208.75.19.79 to 208.75.19.139 ports 22, 17500, 256, 135, 143, 113, 53, ..., ?????uxy, TOS 00 @14:57:26
Aug 16 15:40:20 LIVE272675 scanlogd: 127.0.0.1 to 127.0.0.1 ports 6010, 6011, 48153, 49681, 52321, 33819, 60076, ..., ?????uxy, TOS 00, TTL 64 @16:24:06
Aug 16 15:41:13 LIVE272675 scanlogd: 208.75.19.139 to 208.75.19.139 ports 80, 443, 993, 143, 256, 1720, 8080, 1723, ..., fSrpauxy, TOS 00, TTL 64 @20:41:13
Aug 16 15:49:07 LIVE272675 scanlogd: 208.75.243.17 to 208.75.19.139 ports 1, 2, 3, 7, 9, 11, ..., fSrpauxy, TOS 00, TTL 63 @20:49:07

However, scanning this machine from a machine outside the organization network did not generate any logs, even though the scans detected the ports that were open and the services that were running on the system correctly. Have I got some settings wrong? Or is this something that is expected?

Why is scanlogd missing the scans? Is there a way to detect all port scans?

While MAC addresses are 48 bits, that is a lot more than the 32 bit IPv4 adresses (even counting the reserved addresses 255, 127, Class D Multicast etc ), will we not eventually run out of them?

Also, IPv6 addresses may be derived from the 48 bit MAC addresses. And IPv6 address space is much larger than the MAC address space. So will we not end up with IPv6 addresses without any MAC address to associate with? Or is there an official plan to duplicate MAC addresses?

Also, are bluetooth MAC addresses in the same space as Ethernet mac addresses?

Which of the two HTML snippets perform better?

Including the CSS & JS in the HTML

<html>
 <head>
  <style>
   <?php include("someStyle.css"); ?>
  </style>
  <script>
   <?php include("someScript.js"); ?>
  </script>
 </head>

OR linking the CSS & JS:

<html>
    <head>
        <title>Family Tree</title>
        <script src="someScript.js"></script>
        <link href="someStyle.css" rel='stylesheet' type='text/css' />
    </head>

The logic I can think of is

1. The server receives fewer hits (+server)
2. Parallel transfers are reduced (-browser)
3. DEFLATE performance is improved, if used. (+server)

Will I notice an improvement / degradation for large server loads?

Could anyone suggest me a hypervisor that permits adding RAM to a running virtual machine without restarting the guest OS. Is this even possible? Can this be done on xen? I have never found any documentation for such a thing.

I am trying to set a custom error document in an alias.

Alias /f1 "/media/data/www/f1"
<Directory "/media/data/www/f1">
        AddHandler cgi-script .cgi .pl
        Options Includes Indexes MultiViews FollowSymLinks ExecCGI
        AllowOverride All
        Order allow,deny
        Allow from all
        ErrorDocument 404 "Something was not found!"
</Directory>

This absolutely does not seem to work! The same directives in a virtual host works just fine. What am I doing wrong?

I could not find any reference that states that I cannot have custom error messages in an Alias Section.

I am trying to install fast-cgi for nginx on an EC2 instance. I followed the steps explained here, but that is meant for Debian and does not work out of the box for a red-hat based system. I modified the script a bit to look like -

#!/bin/bash
### BEGIN INIT INFO
# Provides:          php-fcgi
# Required-Start:    $nginx
# Required-Stop:     $nginx
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: starts php over fcgi
# Description:       starts php over fcgi
### END INIT INFO

. /etc/rc.d/init.d/functions

(( EUID )) && echo .You need to have root priviliges.. && exit 1
BIND=/tmp/php.socket
USER=nginx
PHP_FCGI_CHILDREN=15
PHP_FCGI_MAX_REQUESTS=1000

PHP_CGI=/usr/bin/php-cgi
PHP_CGI_NAME=`basename $PHP_CGI`
PHP_CGI_ARGS="- USER=$USER PATH=/usr/bin PHP_FCGI_CHILDREN=$PHP_FCGI_CHILDREN PHP_FCGI_MAX_REQUESTS=$PHP_FCGI_MAX_REQUESTS $PHP_CGI -b $BIND"
RETVAL=0

start() {
      echo -n "Starting PHP FastCGI: "
      #ORIGINAL LINE
      #daemon $PHP_CGI --quiet --start --background --chuid "$USER" --exec /usr/bin/env -- $PHP_CGI_ARGS
      #MODIFIED LINE
      daemon --user=$USER $PHP_CGI -b $BIND&
      RETVAL=$?
      echo
      [ $RETVAL -eq 0 ] && touch /var/lock/subsys/php-fcgi
      #echo "$PHP_CGI_NAME."
}
stop() {
      echo -n "Stopping PHP FastCGI: "
      killall -q -w -u $USER $PHP_CGI
      RETVAL=$?
      echo "$PHP_CGI_NAME."
      rm /var/lock/subsys/php-fcgi
}

case "$1" in
    start)
      start
  ;;
    stop)
      stop
  ;;
    restart)
      stop
      start
  ;;
    *)
      echo "Usage: php-fastcgi {start|stop|restart}"
      exit 1
  ;;
esac
exit $RETVAL

The problem I have now is -

1. service php-fcgi start keeps the shell blocked. If I run service php-fcgi start & and then ps aux, I see the php-cgi process running bound to the socket. I see the start command stop only when I execute service php-fcgi stop. How do I solve this blocking issue? I have tried adding an & at the end of the line spawning the daemon. But other scripts do not seem to be doing this. This is the most complicated script I am attempting to modify yet :-(
2. How do I get the script to display the green [ OK ]? I checked scripts like httpd and saw that all they were doing was something as shown below. But I never see a green [ OK ] when I execute php-fcgi. I also discovered that putting echo_success with functions sourced displays the green [ OK ] but I do not see any other scripts in the /etc/rc.d/init.d/ executing echo_success or echo_failure. What have I got wrong?
3. Also, How do i specify PHP_FCGI_CHILDREN with daemon?

echo
      [ $RETVAL -eq 0 ] && touch /var/lock/subsys/

I have a php file at http://lohray.com/info1.php that is just -

<?php
    phpinfo();
?>

The page does not render on my browsers (I have tried chrome and firefox), however, wget fetches all the HTML. What might be going wrong? My apache / php are running on an EC2 instance.

Using the developer tools, I can see that I have received a 200 header with X-Powered-By:PHP/5.3.10.

I would like to update my hosts file and restart dnsmasq from a web interface (php/apache2). I tried playing around with suid bits (the demonstaration). I have both apache and dnsmasq running on an EC2 instance.

I understand that Linux ignores the setuid bit on text scripts, but works on binary files. (Have I got something wrong?). I added exec("whoami"); to the example C program in Wikipedia. Although the effective UID of the C program is 0, whoami does not return root :-(

I would thoroughly like to avoid

echo password | sudo service dnsmasq restart

or adding apache to the sudoers without password! Is there a way out? How does webmin do such things?

I am trying to implement a dynamic dns service for my computers. I have pointed h.lohray.com to my EC2 instance in the NS record of lohray.com and have installed dnsmasq on that system and have made sure to unblock the firewall port.

For now, I have statistically added an entry on my /etc/hosts file.

129.118.19.163 i7.h.lohray.com

however, i7.h.lohray.com does not resolve correctly with nslookup or dig :-( This is the only time I could have this resolved (online nslookup) - 50.19.103.190 is the IP address of the EC2 instance where dnsmasq is running. Where could I have gone wrong?

I am running a web server on an AWS EC2 micro instance. The instance has ~630MB of RAM. With time, I have several httpd processes and very little free RAM. When I restart the httpd service, I end up freeing about 350MB of RAM.

I thought of having this automated every 12 hours using a cron job under root. My script includes code as

service httpd restart
service mysqld restart
ps aux
free -m

This is the first time I am attempting cron scripts.

I receive an email with the expected output for ps aux and free -m, but

./scriptName.sh: line 1: service: command not found
./scriptName.sh: line 2: service: command not found

for the restarts commands.

The script did run as root. I am afraid that using sudo may cause the script to hang. The relevant lines from the output of ps -

root     14664  0.0  0.2 142200  1720 ?        S    22:41   0:00 CROND
root     14665  0.0  0.2   9296  1236 ?        Ss   22:41   0:00 /bin/sh -c ./scriptName.sh
smmsp    14667  0.0  0.6  76020  4244 ?        R    22:41   0:00 /usr/sbin/sendmail -FCronDaemon -i -odi -oem -oi -t -f root
root     14669  0.0  0.1  11244  1008 ?        R    22:41   0:00 ps aux

What is the right thing to do to have a successful restart of services?

Is it even advisable to do something like this?

Output of free -m

             total       used       free     shared    buffers     cached
Mem:           596        573         23          0          8         71
-/+ buffers/cache:        493        103
Swap:            0          0          0