Re: [BAD] the whole server down with a red-alert-like attack
On Fri, Jan 25, 2002 at 10:28:56AM +1100, Russell Coker wrote: IMHO something that runs every minute should not be in cron, even something that runs every 5 minutes possibly shouldn't be in cron. :) s/should not/must not/ if I do't want problems Yeah, I made a painful experience myself. A shell script that does the following should do: #!/bin/sh while /bin/true ; do /usr/local/bin/something sleep 60 done The problem with this code is that the cycle is slightly greater then 60 seconds. This desynchronize the script very early. As I remember I quick hack my problem with test if a previous run was done. If not, I simply skip this one. So if the script takes hardly any time to run then it runs every minute. If it takes a lot of resources then it'll run only one copy at a time, and have a 1 minute break between runs (time for other programs to get some CPU time etc). What would be handy would be to have a program that did all this, so I could do: /usr/bin/runevery 60seconds /usr/local/bin/something To get the same result as the above shell script. or as I wrote above, something like: #!/bin/sh if previous instance is stil running; then report time presure exit fi do some usefula data gathering and/or processing Then for even more protection it could have options to monitor and/or limit CPU usage and log to syslog. Does this sound good? If I get a dozen people sending me private email stating that they want to use such a program then I'll write it and add it to my logtools package. hmm. doesn't such program exist yet? Main usage for such a program/tool is (from my point of view) data gathering on routers. Someting like an ipac tool does. But sometimes man needs to made its own data gathering scripts. Yes, there are many tools for such a case, but I always love small simple nice handmade scripts. Sorry for my english. I'm not sure with some words like desynchronize. -- Radek Hnilica Radek at Hnilica dot CZ === No matter how far down the wrong road you've gone, turn back. Turkish proverb -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: [BAD] the whole server down with a red-alert-like attack
IMHO something that runs every minute should not be in cron, even something that runs every 5 minutes possibly shouldn't be in cron. Could you tell me why that is so? I often run things from cron that run every 5 mins and have never run into a problem... but then again I often do stupid things repeatedly! :-) Pete -- http://www.elbnet.com ELB Internet Services, Inc. Web Design, Computer Consulting, Internet Hosting -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: [BAD] the whole server down with a red-alert-like attack
On Fri, Jan 25, 2002 at 08:17:31AM -0500, Peter Billson wrote: IMHO something that runs every minute should not be in cron, even something that runs every 5 minutes possibly shouldn't be in cron. Could you tell me why that is so? I often run things from cron that run every 5 mins and have never run into a problem... but then again I often do stupid things repeatedly! :-) Better saying: You can do whatever you want, but think before to not shoot yourself. As I wrote or not: - I ran my script too often - The machine was old 486 - unfortunately conditons has changed due this, the script was runing ten times slowly. And the nighmare was born :) -- Radek Hnilica Radek at Hnilica dot CZ === No matter how far down the wrong road you've gone, turn back. Turkish proverb -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: [BAD] the whole server down with a red-alert-like attack
On Thu, 24 Jan 2002 22:16, Radek Hnilica wrote: I made the same experience with some testing script on one of my routers. I run that script from cron to often. When the conditions were good, the one run end before cron run the next. But once the [...] I resolved my problem with not running that script every minute but relax rules and run it vere five or ten munites. IMHO something that runs every minute should not be in cron, even something that runs every 5 minutes possibly shouldn't be in cron. A shell script that does the following should do: #!/bin/sh while /bin/true ; do /usr/local/bin/something sleep 60 done So if the script takes hardly any time to run then it runs every minute. If it takes a lot of resources then it'll run only one copy at a time, and have a 1 minute break between runs (time for other programs to get some CPU time etc). What would be handy would be to have a program that did all this, so I could do: /usr/bin/runevery 60seconds /usr/local/bin/something To get the same result as the above shell script. Then for even more protection it could have options to monitor and/or limit CPU usage and log to syslog. Does this sound good? If I get a dozen people sending me private email stating that they want to use such a program then I'll write it and add it to my logtools package. -- http://www.coker.com.au/bonnie++/ Bonnie++ hard drive benchmark http://www.coker.com.au/postal/ Postal SMTP/POP benchmark http://www.coker.com.au/projects.html Projects I am working on http://www.coker.com.au/~russell/ My home page -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
