Unix Monitoring

General UNIX Monitoring Tools

The following general purpose UNIX monitoring tools can be used with Oracle Unified Directory.

Tool Description
iostat Provides information about disk I/O and CPU usage.
lsof Provides information about open file descriptors.
lslk Provides information about file system locks.
netstat Provides statistics about network functions.
nslookup Allows you to query DNS servers for information about hosts and domains.
ping Allows you to query the status of a remote host or network gateway.
sar UNIX System V performance monitoring tool.
tcpdump Allows you to debug and monitor network traffic.
top Provides quick, easy monitoring of processes and CPU activities.
trace Provides information about which system calls a process makes.
traceroute Provides the path a packet takes throughout the Internet to reach its final destination.
vmstat Provides statistics about process, virtual memory, disk, trap, and CPU activity.

How to setup an SSH configuration

# How to setup an SSH configuration :

$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/oracle/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/oracle/.ssh/id_rsa.
Your public key has been saved in /home/oracle/.ssh/id_rsa.pub.
The key fingerprint is:
77:7d:c0:10:98:9f:71:55:95:ff:5a:36:2a:69:05:1d oracle@slc03mzv

# Generate the remote hostname keys

$ ssh-keygen -R host.example.com

# Copy the generate key over to the remote hosts.

$ ssh-copy-id oracle@host.example.com

The authenticity of host 'host.example.com (10.244.15.16)' can't be established.
RSA key fingerprint is 4f:43:cb:f2:c7:da:eb:a1:61:0c:9b:cb:42:0c:cb:ac.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'host.example.com' (RSA) to the list of known hosts.
Warning: the RSA host key for 'host.example.com' differs from the key for the IP address '10.244.15.16'
Offending key for IP in /home/oracle/.ssh/known_hosts:1
Are you sure you want to continue connecting (yes/no)? yes
oracle@host.example.com's password:
Warning: untrusted X11 forwarding setup failed: xauth key data not generated
Warning: No xauth data; using fake authentication data for X11 forwarding.
Now try logging into the machine, with "ssh 'oracle@host.example.com'", and check in:

  .ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

# If you get following errors while login, you can update the known_hosts with ip address as well.

$ ssh host.example.com
Warning: the RSA host key for 'host.example.com' differs from the key for the IP address '10.244.15.16'
Offending key for IP in /home/oracle/.ssh/known_hosts:1
Matching host key in /home/oracle/.ssh/known_hosts:13
Are you sure you want to continue connecting (yes/no)? yes
Warning: untrusted X11 forwarding setup failed: xauth key data not generated
Warning: No xauth data; using fake authentication data for X11 forwarding.
Last login: Mon May 23 06:23:16 2016 from dhcp.in.example.com

# If you get any ip address related error, update the ip address in the known_hosts file

$ vi /home/oracle/.ssh/known_hosts

host.example.com, ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEArjg18OaP/3kBgcOQ87DsEwbrEJA4n/e/2E4LBikgptHKfEdlXKh1DQGeLVBjS+cxWGmQ3Q+j2BPci540QwxDaP2zOY/syjJRWQSM1YMAsL+7BJtGCoSgBmdcSBxyZftnUGdl6/81EiuEzfox4yM4pIFbi6yD4ykxk4qPEzDCvEOxqFeHqtCkfxsqRI5quf38QbRHSCYrkgugRGDRSRQMEybksde0GV208JhbjVZUKjnc1xrQP2YcrWY12kfnk+GsGDkAbHPAQZdtH2T4/nywdqJp9vSwXirB2sbVXHiAH0Xf2DSlrplOtb5Hb/Z3NnGnt5q5BMNrSXMfWB+PALjZuQ==

# After setting up the ssh, it will not ask any password when you login to remote host. ( The option Y here enables trusted X11 forwarding )
$ ssh -Y hostname

Ref Links :

https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys–2
http://stackoverflow.com/questions/20840012/ssh-remote-host-identification-has-changed
http://serverfault.com/questions/538045/offending-key-warning-when-i-do-ssh-to-vps