I am currently using a Linux box (CentOS 5.9) as my router. The router is multihomed and uses two ISP to connect to the internet. Internet traffic from the LAN is distributed through both the lines.
When a particular ISP connection goes down I had to manually route the traffic through the other ISP. What is the best way to detect a dead ISP gateway and route traffic through the alternate ISP connection?
How is CPU usage calculated on a Linux system with a single core?
Cpu(s): 28.1%us, 6.5%sy, 0.0%ni, 43.0%id, 21.6%wa, 0.0%hi, 0.5%si, 0.2%st
Please explain me how the us, sy, ni, id, wa, hi, si and st values are obtained.
I am running Ubuntu 10.04 with the below kernel version
Linux ip-10-0-1-119 2.6.32-343-ec2 #45-Ubuntu SMP Tue Feb 14 18:18:17 UTC 2012 x86_64 GNU/Linux
The memory status shows that the cache is using the maximum share of the RAM.
ubuntu@ip-10-0-1-12:~$ free -m
total used free shared buffers cached
Mem: 7702 7657 44 0 24 6137
-/+ buffers/cache: 1494 6207
Swap: 0 0 0
I understand that the OS manages it automatically and keeps the maximum share of RAM in the cache to minimize the cost of I/O.
The problem is during heavy load when our application requires memory and if the same amount is not available in the physical RAM the OOM killer terminates the application.
How can I tune my kernel so that if there is any memory request from my application the kernel should free some of the cache memory to make room for my application instead the OOM killer terminating it ?
We are using Squid proxy server in our environment and we want to cache HTTPS requests.
Is there any way to configure Squid or in general a proxy server to cache HTTPS requests?
I want to monitor all user's activity in my server.
Even when the user executes a shell command from some editor like vim I want to see them in the log file.
I have checked the tool acct but it is not listing the complete commands. (Please correct me if I have missed some options which does already).
Which Linux tool I should be looking at to solve this problem?
I am using monit to monitor all my processes which is matched using.
check process [name] matching [process name pattern]
Monit is able to match using the pattern and "monit procmatch [process name pattern]" lists all the process.
The problem is it is not listing in the web interface, it just displays only the first process.
Is it possible to list all the process in web interface ?
How can I have start and stop commands in monit for all those processes which are matched ?
I have a "downloads" folder inside "tempuser" home folder ("/home/tempuser/downloads") which I want to allow "rwx" permission for a different user say "testuser". The testuser should not have any permission to anyother files or folders inside /home/tempuser other than the "downloads" folder.
How can I do it ?
I want to set an optimum value for MaxClient in apache for my production server. What are the parameters that I should consider while calculating this value ?
My log files are in the format "2011-03-28.log.php". Log files are created every day. I want to keep 5 days log and rest I want to remove it, which means only 5 log files will be kept and rest everything will be deleted.
Is it possible using Linux logrotate ?
I am trying to monitor a log file using Zabbix 1.8.4.
I created an item using the following details:
Host: Zabbix server
Description: logger_test
Type: Zabbix agent (active)
Key: log[/tmp/scribetest/test3/test3_current,error,,100]
Type of Infromation: Log
Update interval (in sec): 1 sec
Keep history (in days): 90
Status: Active
Applications: Log files
I created a trigger and attached it with the item logger_test using the following details:
Name: logger_test_trigger
Expression: {Zabbix server:log[/tmp/scribetest/test3/test3_current,error,,100].str(error)}=1
Severity: disaster
The above settings works fine for the first time but next time the trigger shows ZBX_NOTSUPPORTED and after that item also shows "not supported" message.
Can you please tell me if anything I am doing wrong here ?
with "u32 match ip sport 80" in Linux tc I can match port 80, but how can I match a port range 10000 - 20000 ?
I want to protect SSH access to our live web server from all IP's except our office static IP.
There are some employees who connects to this live server from their dynamic IP's. So, it is not always possible for me to change in the iptables rule in live server whenever the dynamic IP of the employee changes.
I tried to put them in office VPN and allowed only SSH access from office IP but the office connection is slow in compared to our employee's private internet connection, moreover it adds an extra overhead to our office network.
Is there any way I can solve this problem ?
I sometimes face voice break when calling through a VOIP application. Since all VOIP applications uses UDP for data transmission, is there any tool in Linux to measure the amount of packet loss and measure the performance of the network.
What could be the general reason for UDP packet loss and what measures I need to take when there is lot of packet loss ?
I am running MySQL 5.1.36 in all my servers.
I want to replicate database_A from master_host_A and database_B from master_host_B into a single slave server. All the three MySQL servers are remotely located.
Is it possible for me to setup replication of multiple masters to a single slave server ? If yes please let me know how should I approach?
Is it feasible for production servers ?
Warm Regards
Supratik
I am using VirtualDocumentRoot in my Virtual host configuration.
My VirtualDocumentRoot is set to /var/www/%1/ and if I create a folder say test, it is working as expected. The problem is, when I am using $_SERVER["DOCUMENT_ROOT"] in my php files it is retuning /var/www. Is it possible to have php return the same path for $_SERVER["DOCUMENT_ROOT"] as configured in VirtualDocumentRoot.
Is it possible to configure user specific hosts file instead of a common /etc/hosts.
For example if user "user1" tries to get the name for the IP: "127.0.0.1", he gets "dev.user1" and if user "user2" tries to get the name for the same IP, he gets "dev.user2".
A domain abc.com has two web servers located in two different location one in India and another in Malaysia. If the request are handled by the servers depending on the location from where the request originates then how DNS server resolves for such geographically distributed servers when my client system is configured to a local DNS server in Indian or a DNS server in Malyasia ?
Warm Regards
Supratik
How can I create a new Subversion repository from the current one with last 3 months data and purge/backup the remaining of the data?
Is there a solution to this problem?
Can anyone please suggest a way to use a domain name in iptables rules.
Sometimes I am getting the following error
The requested URL could not be retrieved
While trying to retrieve the URL: http://groups.google.com/
The following error was encountered:
Unable to determine IP address from host name for groups.google.com
The dnsserver returned:
Refused: The name server refuses to perform the specified operation.
This means that:
The cache was not able to resolve the hostname presented in the URL. Check if the address is correct.
Your cache administrator is root.
What could be the reason for the above error ?
Regards
Supratik