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Articles indexed Saturday November 2 2013

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• Please explain how Trial Division works for Primality Test

  - by mister_dani

  I came across this algorithm for testing primality through trial division I fully understand this algorithm static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i <= Math.sqrt(N); i++) if (N % i == 0) return false; return true; } It works just fine. But then I came across this other one which works just as good but I do not fully understand the logic behind it. static boolean isPrime(int N) { if (N < 2) return false; for (int i = 2; i * i<N; i++) if (N % i == 0) return false; return true; } It seems like i *i < N behaves like i <= Math.sqrt(N). If so, why?

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• Runtime error in C code (strange double conversion)

  - by Miro Hassan

  I have a strange runtime error in my C code. The Integers comparison here works fine. But in the Decimals comparison, I always get that the second number is larger than the first number, which is false. I am pretty new to C and programming in general, so this is a complex application to me. #include <stdio.h> #include <stdbool.h> #include <stdlib.h> int choose; long long neLimit = -1000000000; long long limit = 1000000000; bool big(a,b) { if ((a >= limit) || (b >= limit)) return true; else if ((a <= neLimit) || (b <= neLimit)) return true; return false; } void largerr(a,b) { if (a > b) printf("\nThe First Number is larger ..\n"); else if (a < b) printf("\nThe Second Number is larger ..\n"); else printf("\nThe Two Numbers are Equal .. \n"); } int main() { system("color e && title Numbers Comparison && echo off && cls"); start:{ printf("Choose a Type of Comparison :\n\t1. Integers\n\t2. Decimals \n\t\t I Choose Number : "); scanf("%i", &choose); switch(choose) { case 1: goto Integers; break; case 2: goto Decimals; break; default: system("echo Please Choose a Valid Option && pause>nul && cls"); goto start; } } Integers: { system("title Integers Comparison && cls"); long x , y; printf("\nFirst Number : \t"); scanf("%li", &x); printf("\nSecond Number : "); scanf("%li", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Integers; } largerr(x,y); printf("\nFirst Number : %li\nSecond Number : %li\n",x,y); goto exif; } Decimals: { system("title Decimals Comparison && cls"); double x , y; printf("\nFirst Number : \t"); scanf("%le", &x); printf("\nSecond Number : "); scanf("%le", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Decimals; } largerr(x,y); goto exif; } exif:{ system("pause>nul"); system("cls"); main(); } }

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• Writing loops with i++ or ++i [duplicate]

  - by Nonesuch

  This question already has an answer here: Why use ++i instead of i++ in cases where the value is not used anywhere else in the statement? 6 answers format of for loops 31 answers I have a question about writing loops. I always begin with (int i=0; i<10; i++) But I see many experts begin with (int i=0; i<10; ++i) Is there there any real difference, or they are same? Of course, I know the difference between pre-increment and post-increment. I mean which one I should use when writing the loop? or it depends. Thanks!

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• List modification in Python

  - by user2945143

  We are given an algorithm to modify a list of numbers from 1 to 28. There are 5 steps in the algorithm. We have written functions for each step (all correct). We need to write a function that combines all 5 steps. The algorithm modifies the list to get a value. Each time you get a new value, you use the list created by the algorithm from the previous step. This is what we have gotten so far for the code: get_card_at_top_index(insert_top_to_bottom(triple_cut((move_joker_2( move_joker_1(deck)))))) When we run the code to generate the get_card_at_top_index, the first answer is correct. However, the rest are not. Instead of using from the new list, python uses the value that it generated from the last step. What did we do wrong? UPDATE: The other 5 codes passed the tests, they are correct. Code 1 (List) = list1 Code 2 (list1) = list2 Code 3 (list2) = list3 Code 4 (list3) = list4 Code 5 (list4) = list5 we generate a number from 5. We need to run the algorithm again to generate 25 more numbers. We will use list 5 start from step 1

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• Defining and using controller methods in ember.js

  - by OriginalEXE

  first of all, I am total noob when it comes to OOP in JS, this is new to me so treat me like a noob. I am building my first ember.js application and I am stuck (not the first time but I would get unstuck by myself, this is a tough one though). I have two models: forms entries Entries is of course in (one to many) relationship to forms, so each form can have as many properties. Form properties: id : DS.attr( 'number' ), title : DS.attr( 'string' ), views : DS.attr( 'number' ), conversion : DS.attr( 'number' ), entries : DS.hasMany( 'entry' ) Entry properties: id : DS.attr( 'number' ), parent_id: DS.belongsTo( 'form' ) Now, I have forms route that displays all forms in tabled view, and each table row has some info like form id, name etc. and that works great. What I wanted to do is display the number of entries each form has. I figured I should do that via controller, so here is my controller now: // Form controller App.FormController = Ember.ObjectController.extend({ entriescount: function() { var entries = this.get( 'store').find( 'entry' ); return entries.filterBy( 'parent_id', this.get( 'id' ) ).get( 'length' ); }.property( '[email protected]_id') }); Now for some reason, when I use {{entriescount}} in {{#each}} loop, this returns nothing. It also returns nothing in single form route. Note that in both cases, {{title}} for example works. I am wondering, am I going the right way by using controller for this, and how do I get controller to output the data. Thanks

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• Linux issues on setting a timer function

  - by laura

  I am creating a process with 2 children, 1 of the children is responsible to read questions (line by line from a file), output every question and reading the answer, and the other one is responsable to measure the time elapsed and notify the user at each past 1 minute about the remaining time. My problem is that i couldn't find any useful example of how i can make this set time function to work. Here is what i have tried so far. The problem is that it outputs the same elapsed time every time and never gets out from the loop. #include<time.h> #define T 600000 int main(){ clock_t start, end; double elapsed; start = clock(); end = start + T; while(clock() < end){ elapsed = (double) (end - clock()) / CLOCKS_PER_SEC; printf("you have %f seconds left\n", elapsed); sleep(60); } return 0; }

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• Dynamic page adding through jsPdf

  - by Vishakh Shetty

  I am trying to convert content from tinymce editor to pdf using Jspdf. But as JSpdf creating single pdf page only initial 30 lines from editors appering in PDF.. So how can I add page dynamically to convert whole content to pdf?? My CODE: function save_to_pdf() { var myIFrame = document.getElementById(text_ifr); var content = myIFrame.contentWindow.document.body.innerHTML; $('#pdf_text').html(content); var pdf = new jsPDF('p', ' in ', 'letter'), source = $('#pdf_text')[0], specialElementHandlers = { '#bypassme': function(element, renderer) { return true; } }; pdf.fromHTML( source, // HTML string or DOM elem ref. 0.5, // x coord 0.5, // y coord { width: 7.5, // max width of content on PDF elementHandlers: specialElementHandlers } ); pdf.addImage(imageData, JPEG, 95, 5, 20, 20); pdf.save(Test.pdf); } Thanks in Advance

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• Avoid Spring ApllicationContext instanciation

  - by Ceddoc

  I use Spring 3 to make a simple configuration. I have an XML file called PropertyBeans.xml like that : <bean id="propertyBean" class="com.myapp.PropertyBean"> <property name="rootDirLogPath" value="C:\Users\dede" /> </bean> I have the bean which match this XML and then I want to use this bean with the value injected. Actually I have : ApplicationContext context = new ClassPathXmlApplicationContext("AppPropertyBeans.xml"); PropertyBean obj = (PropertyBean) context.getBean("propertyBean"); String rootDirLogPath = obj.getRootDirLogPath(); This works great but I want to know if there's a way to avoid the instantiation of ApplicationContext at each time I want to use a bean. I've heard about BeanFactory is that a good idea? Which are the others solutions? In other words: Am I supposed to called this Application context instanciation in every Controller in spring MVC?

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• Can't echo jquery (with ajax) variable in php

  - by Lars Kerff

  I'm trying to post a variable through ajax. But it won't echo the variable in php. This are the variables (these are working, seen in the log): $("#slider").bind("valuesChanged", function(e, data){console.log("min: " + data.values.min + " max: " + data.values.max);}); The Ajax part: $("#slider").bind("valuesChanged", function (e, data) { $.ajax({ type: "POST", dataType: "text", url: "../test.php", data: { minValue: data.values.min, maxValue: data.values.max }, async: false, success: function(data){ alert('yeah') }, error: function(xhr) { alert('fail') // if your PHP script return an erroneous header, you'll land here } }); }); </script> And php echo: <?php if ( $_POST ) { echo $_POST[ 'minValue' ]; } ?> Now why does it not echo the post? Thanks!

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• How do I "think in AngularJS" if I have a jQuery background?

  - by Mark Rajcok

  How do I “think in AngularJS” if I have a jQuery background? Suppose I'm familiar with developing client-side applications in jQuery, but now I'd like to start using AngularJS. Can you describe the paradigm shift that is necessary? Here are a few questions that might help you frame an answer: How do I architect and design client-side web applications differently? What is the biggest difference? What should I stop doing/using; what should I start doing/using instead? Are there any server-side considerations/restrictions? I'm not looking for a detailed comparison between jQuery and AngularJS.

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• Issue with GCD and too many threads

  - by dariaa

  I have an image loader class which provided with NSURL loads and image from the web and executes completion block. Code is actually quite simple - (void)downloadImageWithURL:(NSString *)URLString completion:(BELoadImageCompletionBlock)completion { dispatch_async(_queue, ^{ // dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ UIImage *image = nil; NSURL *URL = [NSURL URLWithString:URLString]; if (URL) { image = [UIImage imageWithData:[NSData dataWithContentsOfURL:URL]]; } dispatch_async(dispatch_get_main_queue(), ^{ completion(image, URLString); }); }); } When I replace dispatch_async(_queue, ^{ with commented out dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ Images are loading much faster, wich is quite logical (before that images would be loaded one at a time, now a bunch of them are loading simultaneously). My issue is that I have perhaps 50 images and I call downloadImageWithURL:completion: method for all of them and when I use global queue instead of _queue my app eventually crashes and I see there are 85+ threads. Can the problem be that my calling dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0) 50 times in a row makes GCD create too many threads? I thought that gcd handles all the treading and makes sure the number of threads is not huge, but if it's not the case is there any way I can influence number of threads?

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• Nginx Tries to download file when rewriting non-existent url

  - by Vince Kronlein

  All requests to a non-existent file should be re-written to index.php?name=$1 All other requests should be processed as normal. With this server block, the server is trying to download all non-existent urls: server { server_name www.domain.com; rewrite ^(.*) http://domain.com$1 permanent; } server { listen 80; server_name domain.com; client_max_body_size 500M; index index.php index.html index.htm; root /home/username/public_html; location ~ /\.ht { deny all; } location ~ \.php$ { try_files $uri = 404; fastcgi_split_path_info ^(.+\.php)(/.+)$; include fastcgi_params; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; fastcgi_pass 127.0.0.1:9002; } location ~* ^.+\.(ogg|ogv|svg|svgz|eot|otf|woff|mp4|ttf|rss|atom|jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|ppt|tar|mid|midi|wav|bmp|rtf)$ { access_log off; log_not_found off; expires max; } location /plg { } location / { if (!-f $request_filename){ rewrite ^(.*)$ /index.php?name=$1 break; } } } I've checked to see that my default_type = text/html instead of octet stream, not sure what the deal is.

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• HP DL160G6 bios update fails

  - by Bojo

  I tried to update the BIOS from my HP DL160G6's. Unfortunately the Windows update degraded my BIOS version from 243 to 237. But when I try to upgrade both servers to version the update fails. First I got a warning like: CMOS Layout difference between System ROM and ROM file has detected. AFU recommand (sic) adding /C commands of your original input commands. Press "A" to accept AFU's recommendation. Press "F" to keep original input commands. And the update did not do anything. But now I get a message like: Reading flash ........ done Bootblock checksum ... ok Module checksums ..... bad Error: BIOS checksum error And the update stops. I tried some commands form this page: http://www.ami.com/support/downloads/txt/AFU_README.TXT But I don't try to much, the servers are still booting. Does anyone know how to update my servers to BIOS version 245? I used this version http://h20565.www2.hp.com/portal/site/hpsc/template.PAGE/public/psi/swdDetails/?sp4ts.oid=3884344&spf_p.tpst=swdMain&spf_p.prp_swdMain=wsrp-navigationalState%3Didx%253D%257CswItem%253DMTX_7bd12651ab954fdcb0d7ee164a%257CswEnvOID%253D54%257CitemLocale%253D%257CswLang%253D%257Cmode%253D%257Caction%253DdriverDocument&javax.portlet.begCacheTok=com.vignette.cachetoken&javax.portlet.endCacheTok=com.vignette.cachetoken and created a bootable USB stick sith HPQUSB.exe

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• Less reboots on Windows Server Core, is this true or just a myth?

  - by Peter Hahndorf

  Because there are less components installed on a Windows Server core OS, it needs less patches than the full OS. I read in several places that therefor it needs less reboots after patching. I'm running Server 2012 core in production since September 2012 now and I don't remember a single patch-Tuesday when I did not have to reboot the server after installing Windows updates. Are there any hard numbers out there that compare the required reboots for core vs. Full OS? Less reboots may be the main reason why people choose to go with Server core. If it actually requires just as many reboots as the full OS install, they may think again the next time they set up a server.

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• Postfix: mail going to spam

  - by Yaro

  All emails I send from my new server go to spam in Gmail (and sometimes yahoo). I've never before sent out mass email or spam. What I've already done: Configured reverse DNS Enabled DKIM Verified my IP is not on spam lists Verified I'm not an open relay Here are the headers from the received message: http://pastie.org/pastes/8450781/text?key=onxgrau1xinyqv7ridxrea Really, can't seem to figure out why the mail just doesn't come through. I'd really appreciate your help. Thank you!

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• BIND9 / DNS Zone / Dedicated Server / Unique Reverse DNS

  - by user2832131

  I locate a dedicated server in a datacenter with no DNS Zone setup. Datacenter panel have 1 textfield only you can fill one Reverse DNS only. According with datacenter instructions here... [instructions]: http://www.wiki.hetzner.de/index.php/DNS-Reverse-DNS/en#How_can_I_assign_several_names_to_my_IP_address.2C_if_different_domains_are_hosted_on_my_server.3F How_can_I_assign_several_names_to_my_IP_address ...I need to install BIND9 in order to configure other records like CNAME and MX. Ok, I've installed BIND9, created a Master Zone. And following this example, I put it in the Zone File: [example]: http://wiki.hetzner.de/index.php/DNS_Zonendatei/en example $ttl 86400 @ IN SOA ns1.first-ns.de. postmaster.robot.first-ns.de. ( 1383411730 14400 1800 604800 86400 ) @ IN NS ns1.first-ns.de. @ IN NS robotns2.second-ns.de. @ IN NS robotns3.second-ns.com. localhost IN A 127.0.0.1 @ IN A 144.86.786.651 www IN A 144.86.786.651 loopback IN CNAME localhost But when I point my domain to ns1.first-ns.de, DNS Register says "time out". Am I missing something? I created a Master zone. Should it be a Slave zone? named.conf: include "/etc/bind/named.conf.options"; include "/etc/bind/named.conf.local"; include "/etc/bind/named.conf.default-zones"; named.conf.options: options { directory "/var/cache/bind"; dnssec-validation auto; auth-nxdomain no; # conform to RFC1035 listen-on-v6 { any; }; }; named.conf.local: zone "mydomain.com" { type master; file "/var/lib/bind/mydomain.com.hosts"; allow-update {any;}; allow-transfer {any;}; allow-query {any;}; }; named.conf.default-zones: zone "." { type hint; file "/etc/bind/db.root"; }; zone "localhost" { type master; file "/etc/bind/db.local"; }; zone "127.in-addr.arpa" { type master; file "/etc/bind/db.127"; }; zone "0.in-addr.arpa" { type master; file "/etc/bind/db.0"; }; zone "255.in-addr.arpa" { type master; file "/etc/bind/db.255"; }; Problem is that I'm moving my site, and can't update the new NS server due to a 'timeout' message when filling new datacenter NS. I'm filling: MASTER: ns1.first-ns.de SLAVE1: robotns2.second-ns.de SLAVE2: robotns3.second-ns.com

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• Safari 7 SSL error if using IP-adress

  - by K. Biermann

  I have created my own CA for internal usage and set the root certificate to trustworthy on my machines. With this CA I signed the SSL-certificates for my internal servers. I only address them with their IP and so I used the servers' IP as certificate name. If i connect to the Servers with Chrome or mobile Safari it works without problems, but if I use Safari 7 under Mavericks (on the same machine with the same keychain) i get the following error: "The certificate is not valid (host name mismatch)". I double checked that I entered the correct IP ("https://192.168.2.130"), but I always get the same error. Do I need to enter a different name for the certificate or is it just that Safari doesn't support SSL certificates for IPs? Here is a screenshot of the error message (I can only post images with at least 10 rep): Safari's error message Thanks in advantage and please excuse my bad English :D

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• How do I make rsync also check ctime?

  - by Benoît

  rsync detects files modification by comparing size and mtime. However, if for any reason, the mtime is unchanged, rsync won't detect the change, although it's possible to spot it by looking at the ctime. Of course, I can tell rsync do compare the whole files' contents, but that's very very expensive. Is there a way to make rsync smarter, for example by checking mtime+size are the same AND that ctime isn't newer than mtime (on both source and destination) ? Or should I open a feature request ? Here's an example: Create 2 files, same content and atime/mtime benoit@debian:~$ mkdir d1 && cd d1 benoit@debian:~/d1$ echo Hello > a benoit@debian:~/d1$ cp -a a b Rsync them to another (non-exisiting) directory: benoit@debian:~/d1$ cd .. benoit@debian:~$ rsync -av d1/ d2 sending incremental file list created directory d2 ./ a b sent 164 bytes received 53 bytes 434.00 bytes/sec total size is 12 speedup is 0.06 OK, everything is synced benoit@debian:~$ grep . d*/* d1/a:Hello d1/b:Hello d2/a:Hello d2/b:Hello Update file 'b', same size and then reset its atime/mtime benoit@debian:~$ echo World > d1/b benoit@debian:~$ touch -r d1/a d1/b Attempt to rsync again: benoit@debian:~$ rsync -av d1/ d2 sending incremental file list sent 63 bytes received 12 bytes 150.00 bytes/sec total size is 12 speedup is 0.16 Nope, rsync missed the change. benoit@debian:~$ grep . d*/* d1/a:Hello d1/b:World d2/a:Hello d2/b:Hello Tell rsync the compare the file content benoit@debian:~$ rsync -acv d1/ d2 sending incremental file list b sent 144 bytes received 31 bytes 350.00 bytes/sec total size is 12 speedup is 0.07 Gives the correct result: benoit@debian:~$ grep . d*/* d1/a:Hello d1/b:World d2/a:Hello d2/b:World

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• website is accessible through dns1. but not with WWW

  - by Pushpendra

  i have a domain and i am using freehostia as a web hoster. In the name server of domain i have registered the name of both servers of freehostia. And in my control panel in the hosted domain section its showing "1 Hosted Domains / 1 Domains Listed".however on clicking on that its showing an error that "The selected domain name has not been registered yet. Please register it from the Domain Manager section first" now whenever i am trying to access my website by using dns1. its accessible but when i am using WWW. its not accessible for example my domain name is example.com if i will type dns1.example.com then my webpage will open but when i type www.example.com its showing "Oops! Google Chrome could not find www.example.com" And for information 24 hours has been passed since i have registered my name servers.

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• Gmail - error adding pop3 account from my mail server (postfix+courier)

  - by Lucas Lobosque

  I use courier to add pop3/imap support to my mail server, and I get this when I try to add a new pop3 account in gmail: Server returned error: "Missing +OK response upon connecting to the server: * OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS] Courier-IMAP ready. Copyright 1998-2011 Double Precision, Inc. See COPYING for distribution information." Any help on how to fix this would be appreciated.

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• Logfiles filling with iptables logging

  - by Peter I

  OS: Debian 6 Server Version I have different logfiles which are filling up: user@server:/var/log$ ls -lahS | head total 427G -rw-r--r-- 1 root root 267G Nov 2 17:29 bandwidth -rw-r----- 1 root adm 44G Nov 2 17:29 kern.log -rw-r----- 1 root adm 27G Nov 2 17:29 debug -rw-r----- 1 root adm 23G Oct 27 06:33 kern.log.1 -rw-r----- 1 root adm 17G Nov 2 17:29 messages -rw-r----- 1 root adm 14G Oct 27 06:33 debug.1 -rw-r----- 1 root adm 12G Nov 2 17:29 syslog -rw-r----- 1 root adm 12G Nov 1 06:26 syslog.1 -rw-r----- 1 root adm 9.0G Oct 27 06:33 messages.1 So I looked up the file /etc/iptables.up.rules which had those lines in it: -A FORWARD -o eth0 -j LOG --log-level 7 --log-prefix BANDWIDTH_OUT: -A FORWARD -i eth0 -j LOG --log-level 7 --log-prefix BANDWIDTH_IN: -A OUTPUT -o eth0 -j LOG --log-level 7 --log-prefix BANDWIDTH_OUT: -A INPUT -i eth0 -j LOG --log-level 7 --log-prefix BANDWIDTH_IN: So deleting those lines will solve my problem. But how would I edit those lines without losing their functionality?

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• Ubuntu server: Delete first folder in directory

  - by Martin

  How can I grab the first subfolder in a directory and delete it? I found a script to monitor the free diskspace. It sends an alert email if space runs low, but I want to also delete some unneeded stuff. I have a backup folder where I save daily and monthly backups. I want to delete the first folder since this always the oldest, but I don't know the name of the oldest backup. My folders without Jan-May and Dec: 06-01 07-01 08-01 09-01 10-01 11-01 Friday Monday Saturday Sunday Thursday Tuesday Wednesday How can I delete the first folder "06-01" without knowing its name?

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• kernel warning disk error for command write - solaris svm

  - by help_me

  Recently this warning came up on my message logs, scsi: [ID 107833 kern.warning] WARNING: /pci@1c,600000/scsi@2/sd@0,0 (sd0): Oct 27 00:14:44 Error for Command: write(10) Error Level:Retryable Oct 27 00:14:44 scsi: [ID 107833 kern.notice] Requested Block: 101515828 Error Block: 101515828 Oct 27 00:14:44 scsi: [ID 107833 kern.notice] Vendor: SEAGATE Serial Number: 0441B9B5H Oct 27 00:14:44 scsi: [ID 107833 kern.notice] Sense Key: Hardware Error Oct 27 00:14:44 scsi: [ID 107833 kern.notice] ASC: 0x19 (defect list error), ASCQ: 0x0, FRU: 0x2 This is showing signs of disk failing in my opinion. I have not seen the messages re-occurring. This is on a Solaris 9 Sparc system V240. The disks are managed by SVM and "metadb" is showing the flags as "a" Are there any tests or indications as to check/see if the disk is actually failing or was that error message initiated by something else. Thank you!

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• Fibre channel long distance woes

  - by Marki

  I need a fresh pair of eyes. We're using a 15km fibre optic line across which fibrechannel and 10GbE is multiplexed (passive optical CWDM). For FC we have long distance lasers suitable up to 40km (Skylane SFCxx0404F0D). The multiplexer is limited by the SFPs which can do max. 4Gb fibrechannel. The FC switch is a Brocade 5000 series. The respective wavelengths are 1550,1570,1590 and 1610nm for FC and 1530nm for 10GbE. The problem is the 4GbFC fabrics are almost never clean. Sometimes they are for a while even with a lot of traffic on them. Then they may suddenly start producing errors (RX CRC, RX encoding, RX disparity, ...) even with only marginal traffic on them. I am attaching some error and traffic graphs. Errors are currently in the order of 50-100 errors per 5 minutes when with 1Gb/s traffic. Optics Here is the power output of one port summarized (collected using sfpshow on different switches) SITE-A units=uW (microwatt) SITE-B ********************************************** FAB1 SW1 TX 1234.3 RX 49.1 SW3 1550nm (ko) RX 95.2 TX 1175.6 FAB2 SW2 TX 1422.0 RX 104.6 SW4 1610nm (ok) RX 54.3 TX 1468.4 What I find curious at this point is the asymmetry in the power levels. While SW2 transmits with 1422uW which SW4 receives with 104uW, SW2 only receives the SW4 signal with similar original power only with 54uW. Vice versa for SW1-3. Anyway the SFPs have RX sensitivity down to -18dBm (ca. 20uW) so in any case it should be fine... But nothing is. Some SFPs have been diagnosed as malfunctioning by the manufacturer (the 1550nm ones shown above with "ko"). The 1610nm ones apparently are ok, they have been tested using a traffic generator. The leased line has also been tested more than once. All is within tolerances. I'm awaiting the replacements but for some reason I don't believe it will make things better as the apparently good ones don't produce ZERO errors either. Earlier there was active equipment involved (some kind of 4GFC retimer) before putting the signal on the line. No idea why. That equipment was eliminated because of the problems so we now only have: the long distance laser in the switch, (new) 10m LC-SC monomode cable to the mux (for each fabric), the leased line, the same thing but reversed on the other side of the link. FC switches Here is a port config from the Brocade portcfgshow (it's like that on both sides, obviously) Area Number: 0 Speed Level: 4G Fill Word(On Active) 0(Idle-Idle) Fill Word(Current) 0(Idle-Idle) AL_PA Offset 13: OFF Trunk Port ON Long Distance LS VC Link Init OFF Desired Distance 32 Km Reserved Buffers 70 Locked L_Port OFF Locked G_Port OFF Disabled E_Port OFF Locked E_Port OFF ISL R_RDY Mode OFF RSCN Suppressed OFF Persistent Disable OFF LOS TOV enable OFF NPIV capability ON QOS E_Port OFF Port Auto Disable: OFF Rate Limit OFF EX Port OFF Mirror Port OFF Credit Recovery ON F_Port Buffers OFF Fault Delay: 0(R_A_TOV) NPIV PP Limit: 126 CSCTL mode: OFF Forcing the links to 2GbFC produces no errors, but we bought 4GbFC and we want 4GbFC. I don't know where to look anymore. Any ideas what to try next or how to proceed? If we can't make 4GbFC work reliably I wonder what the people working with 8 or 16 do... I don't assume that "a few errors here and there" are acceptable. Oh and BTW we are in contact with everyone of the manufacturers (FC switch, MUX, SFPs, ...) Except for the SFPs to be changed (some have been changed before) nobody has a clue. Brocade SAN Health says the fabric is ok. MUX, well, it's passive, it's only a prism, nature at it's best. Any shots in the dark? APPENDIX: Answers to your questions @Chopper3: This is the second generation of Brocades exhibiting the problem. Before we had 5000s, now we have 5100s. In the beginning when we still had the active MUX we rented a longdistance laser once to put it into the switch directly in order to make tests for a day, during that day of course it was clean. But as I said, sometimes it's clean just like that. And sometimes it's not. Alternative switches would mean to rebuild the entire SAN with those only to test. Alternative SFPs, well they're hard to come by just like that. @longneck: The line is rented. It's a dark fibre (9um monomode) so there's noone else on it. Sure there are splices. I can't go and look but I have to trust they have been done correctly. As I said the line has been checked and rechecked (using an optical time-domain reflectometer). Obviously you don't have all this equipment yourself because it's way too expensive. @mdpc: What would be the "wrong" type of cable according to you? Up to the switch everything is monomode, yes. The connectors are the correct ones too. Yeah I know there are the green ones where the fibre is cut off at a certain angle etc. But we have the correct ones for all that I know. Progress Report #1 We have had two fabrics (=2x2 switches) with Brocade 5100s with FabricOS 6.4.1 and two fabrics (another 2x4 switches) on FabricOS 7.0.2. On the longdistance ISLs (one in each fabric) it turned out that with FOS 6.4.1 setting it to long distance issues warnings about the VC Init setting and consequently the fill word. But those are only warnings. FOS 7.0.2 requires you to do modifications to VCI and the fillword for long distance links. Setting FOS 6.4.1 to the LS (long-distance static distance) setting with wrong VCI and fillword setting made the whole fabric inoperational (stuck in an SCN loop, use fabriclog -s to see, you don't see it anywhere else, no port error counters or anything increasing). Currently I'm giving the one fabric with the IMHO more correct settings a beating and it seems to do fine, whereas the other one without much traffic still has errors here and there. In short: We have eliminated the active part of the MUX (the FC retimer). We are putting the long distance SFPs into the end equipment themselves. Just to be sure we bought new monomode cables to connect the end equipment to the remaining passive part of the MUX. We are now trying out several long distance configs. It's almost black magic. Everything that happens is mostly empirical, noone seems to have a clue what are the exact reasons to do something. ("We have tried this, and it didn't work, then we tried that and it worked, so we stuck with that." But noone really seems to know why.) I'll keep you updated. Progress Report #2 We got the new lasers for one of the fabrics on warranty. It's ultra clean even on 4GbFC. They're transmitting with roughly 2mW (3dBm) whereas the others are only at 1.5mW (1.5dBm) although that should really be enough. The other fabric (where the lasers are apparently ok) still produces one or two CRCs infrequently. Using sfpshow the SFP producing the actual RX errors shows Status/Ctrl: 0x82 Alarm flags[0,1] = 0x5, 0x40 Warn Flags[0,1] = 0x5, 0x40 Now I'll have to find out what that means. Not sure if it was there before. Well I'll first clear my head with a week of vacation. 8-)

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• krenew command not working : Permission Denied

  - by prathmesh.kallurkar

  I am using a Linux server to perform my simulations. The login and the file-system of the server are protected using kerberos. The file-system is supported using NFS. Since my simulations take a lot of time to run, my ssh sessions used to hang regularly. So, I have started running my simulations in byobu (similar to screen). In order to make sure that my kerberos session remains active, I am using the krenew command. I have entered the following command in my .bash_profile file. (I am sure that it is called for every login) killall -9 krenew 2> /dev/null krenew -b -t -K 10 So everytime I ssh to the server, I kill the existing krenew command. Then, I spawn a new krenew command -b (which runs in background), -t (I forgot why I was using this option !), and -K 10 (It must run after every 10 minutes and refresh the kerberos cache). When I run the simulations, It runs for 14 hours and then suddenly, I am getting error for reading file Permission Denied Is the command that I am running incorrect ??

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