[207] several possible causes of Apache crash

Recently, the number of website visits has increased rapidly , So a lot of questions came out , Tossed for days , Write down some operation summary , Sharing , Let's talk about it first. Apache Some possibilities of crash and corresponding treatment methods , From the simplest troubleshooting ：

1, Insufficient disk space

This is the most easily overlooked problem , Today's disks are cheap , Most people have a lot of spare disk space , Don't take it for granted that it's not your disk space problem , Maybe it's a log ？ Or your cache file suddenly eats up your disk ？df -h Let's do something easy , Lack of disk space can cause a lot of strange phenomena ,Apache The process keeps piling up without releasing , Because of the emergence of “could not make child process * exit,attemption to continue anyway…” And so on , Last Apache Eat up the memory of the whole machine ,SSH Can not login , You can't Reboot, You can't Kill process ,, You can only restart by force

2, Check Apache The log of has reached 2G！！

You usually have a rough estimate of your own log , But check Apache The log size of is also necessary , especially Apache Of Access journal , But recently some extremely boring so-called garbage people , Constantly scan the directory of your machine , Trying to download your... On your machine Wwwroot.rar, Download your Data.mdb, The grass , Still yours PHP Scan your script directory Upload.asp file ,（ Do a Rewrite, Feed these to scan some Trojans or advertisements , ha-ha , That's what I did ）, Such garbage people give Apache Of Error Logs generate a lot of junk information . If Apache The log reaches 2G（ Limit ）,Apahce There may be some strange phenomena that cannot be explained ,Httpd The process could not be started , Or as soon as it starts , It stopped immediately .

3,DDos attack

Usually this kind of method is troublesome to check and handle , Eliminate the cause of your machine itself ,Apache Reasons for configuration , Find out Apache Still keep breaking down , Where can I monitor the server network connection , Use the script to check the connection ：netstat -na|grep ESTABLISHED|awk ‘{print $5}’|awk -F: ‘{print $1}’|sort|uniq -c|sort -r -n, Or count the number of requests IP（netstat -an | grep -v LISTEN | awk ‘{print $5}’ | awk ‘BEGIN { FS=”:” } { Num[$1]++ } END { for(i in Num) if(Num[i]>8) { print i} }’ | xargs -i[] iptables -I INPUT -s [] -j DROP）, Just shut them down , Yes DDos Usually there is no good soft defense , If the money allows , Where can I buy a better hard defense .

I have executed the above order , It may be to implement the above prevention ip Too many requests .

about DDos attack , The host is hosted in another place , Or it is inconvenient to go to the computer room , Where it is difficult to monitor and process , When your machine crashes , Your remote SSH I can't get in at all , Extremely depressed .

Apache There is an anti DDos Module mod_evasive（mod_evasive See here for the installation of ）, There is no way to evaluate its effect , But at least it can help you record DDos Over here IP, It's too much DDos, Where can I call the police directly .