nitins's questions

I compiled OpenSSH_6.6p1 on one of our server. I am able login via SSH to the upgraded server. But I am not able to connect to other servers running OpenSSH_6.6p1 or OpenSSH_5.8 from this. While connecting I am getting an error as below.

Read from socket failed: Connection reset by peer

On the destination server in the logs, I am seeing it as below.

sshd: fatal: Read from socket failed: Connection reset by peer [preauth]

I tried specifying the cipher_spec [ ssh -c aes128-ctr destination-server ] as mentioned in ssh 'connection reset by peer' problem since 5.8p1 (archived version) and was able to connect. How can configure ssh to use the cipher by default? Why is the cipher required here?

Recently started using ansible. We have servers where the application is setup under different users, like in server xyz.com, unix user is xyz_user and so on.

So in case of xyz.com,

ansible xyz.com -a 'command' -u xyz_user -K

How can we set the sudo user in ansible config so as to automatically sudo to the particular user defined for the server?

My playbook is as below:

- hosts : mygroup
  user : user
  sudo : yes
  tasks :
  - name : Copy script
    copy : 'src=/home/user/Scripts/logchecker.py dest=/opt/root2/logchecker.py owner=root group=root mode=755'
  - name : Execute script
    command : '/usr/bin/python /opt/root2/logchecker.py'

The file upload is working, But execution is failing. Even though I am able to execute the script without any issues directly on the server. Am I doing anything wrong?

The Linux server is hosted in EST timezone. But I want to translate the output of date command to IST(Indian Standard time +5:30 hrs) format and use it in a shell script. Is there any option available for date command to do this or have manually add/subtract hours.

Some of the files we receive on our Redhat server are showing date different from upload date as the last modification time. For us the modification time is important as we classify files depending on date we receive it. Some of these file show earlier timestamps, maybe that of files original creation/modification date on client machine.

Any way check and notify if some one made a change/addition to cronjobs for a particular user on a Linux server?

Is it possible to know the changes made too?

We have squid 3 installed at our Linux gateway server. We have enabled caching. Can it cache objects from https sites ?

I am having Squid 3.1.18 installed. I want to limit the maximum bandwidth any IP can use to 128 Kbps. Is it possible using squid ?

I am not using squid authentication so identifying users and setting limit is not an option. Need some way to limit for local IP addresses connecting to squid to access Web.

I want a cronjob to run at 10:20 and 12:45. Is it possible to set it in one line using cron ?

I know I can add to two similar lines one for 10:20 and another for 12:45.

We have configured Nagios with check_load via NRPE plugin to monitor server load, it reports when load is high, but does not have option to take a snapshot top processes (like top command) at that time.

Are there any nagios NRPE plug-ins for that?

I am trying to implement account lockout for Ubuntu systems using pam_tally. The login should be disabled for certain interval on 3 invalid login attempts. This should happen for both system and LDAP logins to the system.

(We have a working LDAP central authentication system where users from Ubuntu clients can authenticate)

How can we configure this ? I could see some articles on this for redhat but not ubuntu

We have our LAN set up with DHCPD providing fixed IP addresses to the systems. However we are facing IP address conflicts if some one connects a laptop and assigns an IP address belonging to another system.

Is there a way to prevent this? Or ways to detect computers causing this?

I have been using bash for most of my system administration tasks. I also know a bit of perl.

Should I learn Python or Perl is better for system automation. So far from my experience learning perl has been easy.

What ACL should be added slapd.conf to allow users to change their password. We are now having the default ACL allowing only rootdn the rights to modify while allowing reading by everyone including anonymous.

How can you calculate the number of days since 1/1/1970? This is for updating the shadowLastChange attribute on OpenLDAP.

Is there a way to do this using the linux date command?

How many nameserver entries can I give in /etc/resolv.conf? I have given our ISP's 2 nameserver entries as first and second. But since they have issues sometimes, I would like to add Google public nameserver enry. Does a 3rd & 4th entry make any difference?

This is the resolv.conf on our proxy(squid) server. I understand that Squid uses /etc/resolv.conf for name resolution.

We need to setup an intrusion detection system (IDS) on our linux proxy server. Please suggest intrusion detection systems ? anything else than Snort ?

And ... does snort have a good web interface ?

I would like to limit failure retries on my Fedora machine to 5. I think I can accomplish it with PAM. But was unable to to do this.

I have referred to this article to do this

http://www.puschitz.com/SecuringLinux.shtml

Please provide suggestions

My understanding is:

• AddHandler - for server
• AddType - for client (browser)

AddType application/x-httpd-php4 .php4
AddHandler application/x-httpd-php4 .php4

But why do we need to add both? Is both needed in case of PHP? Is AddType needed for PHP?

I know that a dedicated IP is needed for setting up SSL. What happens if we add SSL for domains sharing an IP ? (Namevirtualhost)