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server_administration [2016/05/26 21:14]
sgripon [fail2ban and UFW]
server_administration [2016/12/28 12:06] (current)
sgripon [logwatch]
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-====== Server Administration ======+====== ​Linux Server Administration ======
 ~~socialite~~ ~~socialite~~
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   sudo service fail2ban restart   sudo service fail2ban restart
-===== ddos-deflate ​=====+===== Under DDOS attack? ​=====
-This is a simple script that automatically ban ip when the number ​of connections exceed what is configured. See https://​​en/​news/​item/​20.+The following command can help you identify ddos attacks and IP adresses which are at the source ​of the attack:
-**Note**: ​if you have an error "$CONF not found" when running the script, you mau change the first line of the script from: +  netstat -ntu | awk '{if(NR>​2)print ​$5}' | cut -d-f1 | sort | uniq -c | sort -n
- +
-  #!/bin/sh+
   ​   ​
-to:+It will print for each connected IP the count of open connections:
-  #!/bin/bash +      5 
-   +      158 yyy.yyy.yyy.yyy 
-Same thing in the cron job.+       
 +Usually when you have a high number of open connections,​ like here for yyy.yyy.yyy.yyy,​ it is probably that this ip tries to DDOS you. That's time to ban it using ufw. 
 +===== nmd =====
-There is also an issue with cron service ​name. Raplace ​in the file all occurrences of  +No More DDOS (nmd) is a simple script that automatically ban ip when the number of connections exceed what is configured. See http://​​system-admin/​linux/​17--debian-ubuntu-centos-block-ddos-attacks-with-no-more-ddos-formerly-ddos-deflate.html. (By Lionel Eppe) 
-  ​service crond restart + 
-   +I modified a little the script in order to use ufw to ban adresses. Also, there is an issue with the installed ​cron script: 
-with +  - The name of the cron script must not contain dot (modify CRON variable in ///​usr/​local/​nmd/​ndm.conf/​agent.conf//​. 
-  ​service ​cron restart+  - The second cron command ​in the file miss the user root 
 +The good cron script must look like this: 
 +<file bash /etc/cron.d/​nmd>​ 
 +* * * * * root /​usr/​local/​nmd/​ >> /​var/​log/​nmd-agent.log 2>&​1 
 +0 0 */7 * 0 root echo  > /​var/​log/​nmd-agent.log 2>&​1 
 ==== Use IPTables to limit NEW traffic on port 80 and 443 ==== ==== Use IPTables to limit NEW traffic on port 80 and 443 ====
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   ​   ​
 After that, you should be able to login via ssh without the need of the password. After that, you should be able to login via ssh without the need of the password.
 +===== logwatch =====
 +Logwatch can send you a formatted view of system logs every morning by email. It is usefull to check everyday the health of your server.
 +First, copy default config file to change settings:
 +  sudo cp /​usr/​share/​logwatch/​default.conf/​logwatch.conf /​etc/​logwatch/​conf/​
 +Then, to receive by email the report modify the cron job and add --mailto option :
 +<file bash /​etc/​cron.daily/​00logwatch>​
 +#Check if removed-but-not-purged
 +test -x /​usr/​share/​logwatch/​scripts/​ || exit 0
 +/​usr/​sbin/​logwatch --output mail --mailto
 +===== Slow server diagnostic =====
 +See a very good flow chart to help in slow server cases : http://​​articles/​2014/​07/​31/​slow_server_flow_chart
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server_administration.1464290082.txt.gz · Last modified: 2016/05/26 21:14 by sgripon