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• Server 2003 and XP Client; Why are HTTP connections being silently dropped.

  - by Asa Yeamans

  On my network, my edge-router, a windows 2003 r2 server router with all the latest updates, will drop packets, but only under specific circumstances. I have troubleshot and isolated it down to the most simple configuration i can. There is NO NAT involved. Only fully-public IP addresses. No Firewalls are running either, all ahve been disabled. no packet filters on any interfaces anywhere either. I have a single Windows XP virtual machine and my edge-router(the windows 2003 r2 server, and also a virtual machine) running on a windows 2008 x64 r2 system (running virtual server 2005 as i dont have Intel-VT compatible chip yet). The edge router can access any external http site just fine, no issues. However the windows XP machine is only able to access certain sites. These work: www.google.com www.txstate.edu www.workintexas.com www.thedailywtf.com . These Dont: www.yahoo.com www.utexas.edu en.wikipedia.org slashdot.org www.bing.com. I have removed all possibility of DNS issues by connecting with net-cat from the XP box and sending GET /\r\nHost: \r\n\r\n and that connection replicates the issue as well. The network setup: My statically assigned IP block: x.x.x.168/29 DSL Modem -----PPPoE Connection---- x.x.x.169[EdgeRouter] [EdgeRouter]x.x.x.170 -----Virtual Ethernet----- x.x.x.174 [Test2] Test2's Default gateway is x.x.x.170 and test2 can ping any and every valid, accessible, public IP address with no packet loss what-so-ever. If i connect directly over PPPoE from test2 (the XP box) everything works just fine... Im at my wits end, i have NO IDEA whats causing this.

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• logrotate: neither rotate nor compress empty files

  - by Andrew Tobey

  i have just set up an (r)syslog server to receive the logs of various clients, which works fine. only logrotate is still not behaving as intending. i want logrotate to create a new logfile for each day, but only to keep and store i.e. compress non-empty files. my logrotate config looks currently like this # sample configuration for logrotate being a remote server for multiple clients /var/log/syslog { rotate 3 daily missingok notifempty delaycompress compress dateext nomail postrotate reload rsyslog >/dev/null 2>&1 || true endscript } # local i.e. the system's very own logs: keep logs for a whole month /var/log/kern.log /var/log/kernel-info /var/log/auth.log /var/log/auth-info /var/log/cron.log /var/log/cron-info /var/log/daemon.log /var/log/daemon-info /var/log/mail.log /var/log/rsyslog /var/log/rsyslog-info { rotate 31 daily missingok notifempty delaycompress compress dateext nomail sharedscripts postrotate reload rsyslog >/dev/null 2>&1 || true endscript } # received i.e. logs from the clients /var/log/path-to-logs/*/* { rotate 31 daily missingok notifempty delaycompress compress dateext nomail } what i end up with is having is some sort of "summarized" files such as filename-datestampDay-Day and corresponding .gz files. What I do have are empty files, which are eventually zipped. so does the notifempty directive is in fact responsible for these DayX-DayY files, days on which really nothing happened? what would be an efficient way to drop both, empty log files and their .gz files, so that I eventually only keep logs/compressed files that truly contain data?

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• processes slow after some time of actively running

  - by Yervand Aghababyan

  i have several cron jobs running on an ubuntu machine. each one does some pretty heavy load stuff. The cron jobs are parsing files and the bigger the file the longer it takes them to parse it. The strange thing is that if i make the files too big ( like 30mb) the script kind of hangs. It starts processing them really enthusiastically but after some time (something like 5-10 minutes) the cpu usage of the process drops a lot and it gets into some "zombie" state. If prior to this the process in htop was using 70-80% of the CPU then after this drop occurs it slows down to something like 5-10%. the load average drops down as well. The status of the processes sometimes changes to D in htop, which AFAIR stands for zombie. Today i noticed the same behavior of processes of mysql when executing heavy queries (a query took something like 4 hours to execute). the cron jobs are mostly php and during their processing most of the CPU eats the php process and not mysql. so i think the issue is not with a specific language/program but with the way the processes are "managed". The only other place i've seen similar behavior was on my Amazon EC2 micro instance when after some aggressive use of CPU the CPU quota was taking effect and everything was slowing down dramatically. This is a dedicated machine running ubuntu. what may be the cause?

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• ssh many users to one home

  - by filippo

  Hiya, I want to allow some trusted users to scp files into my server (to an specific user), but I do not want to give these users a home, neither ssh login. I'm having problems to understand the correct settings of users/groups I have to create to allow this to happen. I will put an example; Having: MyUser@MyServer MyUser belongs to the group MyGroup MyUser's home will be lets say, /home/MyUser SFTPGuy1@OtherBox1 SFTPGuy2@OtherBox2 They give me their id_dsa.pub's and I add it to my authorized_keys I reckon then, I'd do in my server something like useradd -d /home/MyUser -s /bin/false SFTPGuy1 (and the same for the other..) And for the last, useradd -G MyGroup SFTPGuy1 (then again, for the other guy) I'd expect then, the SFTPGuys to be able to sftp -o IdentityFile=id_dsa MyServer and to be taken to MyUser's home... Well, this is not the case... SFTP just keeps asking me for a password. Could someone point out what am I missing? Thanks a mil, f. [EDIT: Messa in StackOverflow asked me if authorized_keys file was readable to the other users (members of MyGroup). Its an interesting point, this was my answer: Well, it wasn't (it was 700), but then I changed the permissions of the .ssh dir and the auth file to 750 though still no effect. Guess it's worth mentioning that my home dir ( /home/MyUser) is also readable for the group; most dirs being 750 and the specific folder where they'd drop files is 770. Nevertheless, about the auth file, I reckon the authentication would be performed by the local user on MyServer, isn't it? if so, I don't understand the need for other users to read it... well.. just wondering. ]

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• Windows VPN always disconnects after < 3 minutes, only from my network

  - by hemp

  First, this problem has existed for almost two years. Until serverfault was born, I pretty much gave up on solving it - but now, hope is reborn! I've set up a Windows 2003 server as a domain controller and VPN server at a remote office. I am able to connect to and work over the VPN from every windows client I've tried, including XP, Vista, and Windows 7 without issue, from at least five different networks (corporate and home, domain and non.) It works fine from all of them. However, whenever I connect from clients on my home network, the connection drops (silently) after 3 minutes or less. After a short while, it will eventually tell me the connection has dropped and attempt to redial/reconnect (if I've configured the client that way.) If I reconnect, the connection will re-establish and appear to work correctly, but again will silently drop, this time after a seemingly shorter time period. These are not intermittent drops. It happens every single time, in exactly the same way. The only variable is how long the connection survives. It doesn't matter what type of traffic I send. I can sit idle, send continuous pings, RDP, transfer files, all of that at once - it makes no difference. The result is always the same. Connected for a few minutes, then silent death. Since I doubt anyone has experienced this exact situation, what steps can I take to troubleshoot my evanescing VPN?

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• IP tables blocking access to most hosts but some accesses being logged

  - by epo

  What am I getting wrong? A while back I locked down my web hosting service while hardening it or at least trying to. Apache listens on port 80 only and I set up iptables using the following: IPS="list of IPs" iptables --new-chain webtest # Accept all established connections iptables -A INPUT --protocol tcp --dport 80 --jump webtest iptables -A INPUT --match state --state ESTABLISHED,RELATED --jump ACCEPT iptables -A webtest --match state --state ESTABLISHED,RELATED --jump ACCEPT for ip in $IPS; do iptables -A webtest --match state --state NEW --source $ip --jump ACCEPT done iptables -A webtest --jump DROP However looking at my apache logs I notice various log entries in access_log, e.g. 221.192.199.35 - - [16/May/2010:13:04:31 +0100] "GET http://www.wantsfly.com/prx2.php?hash=926DE27C156B40E55E4CFC8F005053E2D81E6D688AF0 HTTP/1.0" 404 206 "-" "Mozilla/ 4.0 (compatible; MSIE 6.0; Windows NT 5.0)" 201.228.144.124 - - [16/May/2010:11:54:16 +0100] "GET /w00tw00t.at.ISC.SANS.DFind:) HTTP/1.1" 400 226 "-" "-" 207.46.195.224 - - [16/May/2010:04:06:48 +0100] "GET /robots.txt HTTP/1.1" 200 311 "-" "msnbot/2.0b (+http://search.msn.com/msnbot.htm)" How are these slipping through? I don't mind the indexing bots (though I am a little surprised to see them get through). I suppose they must be getting through using the ESTABLISHED,RELATED rules. And no, I can't for the life of me remember why the first match state rule is there So 2 questions: is there a better way to set up iptables to restrict access to specified hosts? How exactly are these 3 examples slipping through?

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• kde dropping keyboard

  - by shabbychef

  I am having problems with KDE 'dropping' my keyboard. It happens periodically when using my gentoo box directly, but has become much worse when accessing via NX (from a Mac laptop). Some possibly irrelevant clues: it appears to happen more often when the system is under higher CPU load the mouse continues to work, but no windows will accept any kind of keyboard focus. kwin will not accept tabbing between windows. when working on the machine directly, I can ctrl-alt-F1 to get to a shell (obviously this does nothing over NX). so I think it is KDE and not xorg. am running kwin-4.3.5-r1, and KDE-4.3.5 generally. this problem definitely appeared after upgrading to kde-4.x, but I do not remember if it appeared in kde-4.2. sometimes the keyboard will reappear, but sometimes I have to kill my kde session. playing with accessibility options or window-focus-stealing options in system-settings under kde will often make the keyboard responsive again, only to drop it perhaps minutes later. I had read online this might be an evdev problem under X (again, I think this is KDE, not X, but will try anything). as a result, I have fiddled with my xorg.conf endlessly. I even deleted it entirely and let nvidia-xconfig have a stab at it, with no luck I am tearing my hair out over this. I have done emerge -e xorg-server and am right now doing emerge -e kwin, to rebuild all packages that might be relevant. no luck with the xorg-server rebuild. any help appreciated. thanks,

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• Preventing endless forwarding with two routers

  - by jarmund

  The network in quesiton looks basically like this: /----Inet1 / H1---[111.0/24]---GW1---[99.0/24] \----GW2-----Inet2 Device explaination H1: Host with IP 192.168.111.47 GW1: Linux box with IPs 192.168.111.1 and 192.168.99.2, as well as its own route to the internet. GW2: Generic wireless router with IP 192.168.99.1 and its own route to the internet. Inet1 & Inet2: Two possible routes to the internet In short: H has more than one possible route to the internet. H is supposed to only access the internet via GW2 when that link is up, so GW1 has some policy based routing special just for H1: ip rule add from 192.168.111.47 table 991 ip route add default via 192.168.99.1 table 991 While this works as long as GW2 has a direct link to the internet, the problem occurs when that link is down. What then happens is that GW2 forwards the packet back to GW1, which again forwards back to GW2, creating an endless loop of TCP-pingpong. The preferred result would be that the packet was just dropped. Is there something that can be done with iptables on GW1 to prevent this? Basically, an iptables-friendly version of "If packet comes from GW2, but originated from H1, drop it" Note1: It is preferable not to change anything on GW2. Note2: H1 needs to be able to talk to both GW1 and GW2, and vice versa, but only GW2 should lead to the internet TLDR; H1 should only be allowed internet access via GW2, but still needs to be able to talk to both GW1 and GW2. EDIT: The interfaces for GW1 are br0.105 for the '99' network, and br0.111 for the '111' network. The sollution may or may not be obnoxiously simple, but i have not been able to produce the proper iptables syntax myself, so help would be most appreciated. PS: This is a follow-up question from this question

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• Ubuntu 10.04 network manager issues

  - by Shark

  I was using the default network manager to connect to my wi-fi network, but if the connection is dropped or router restarted the network manager wont reconnect automatically after i guess a couple of tries and just gives a pop-up to connect manually . To avoid this annoyance I installed WICD but though it does try to reconnect to the network after a drop in connection it is unable to resolve the ip address and i am left with an even bigger annoyance . 1. Is there a way to counter either of these issues ? 2. Something like a background process that will check network status periodically and then try to connect to a favored network ? Edit- out put of lshw -C network *-network description: Wireless interface product: Broadcom Corporation vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:12:00.0 logical name: eth1 version: 01 serial: c0:cb:38:18:9b:7f width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=wl0 driverversion=5.60.48.36 ip=192.168.11.2 latency=0 multicast=yes wireless=IEEE 802.11 resources: irq:17 memory:fbc00000-fbc03fff *-network description: Ethernet interface product: RTL8101E/RTL8102E PCI Express Fast Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:13:00.0 logical name: eth0 version: 02 serial: f0:4d:a2:94:2d:74 size: 10MB/s capacity: 100MB/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half latency=0 link=no multicast=yes port=MII speed=10MB/s resources: irq:29 ioport:e000(size=256) memory:d0b10000-d0b10fff(prefetchable) memory:d0b00000-d0b0ffff(prefetchable) memory:fb200000-fb21ffff(prefetchable)

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• Failed none and iptables

  - by Michael

  The problem is that when I ssh to my host with putty and enter user name, after that the password prompt delays. Found this is directly related to my iptables and can solve by changing default policy to ACCEPT. If default INPUT policy is ACCEPT, then password prompt is coming immediately. Mar 13 00:05:01 server-ubuntu sshd[6154]: Connection from 192.168.0.10 port 26304 Mar 13 00:05:06 server-ubuntu sshd[6154]: Failed none for acid from 192.168.0.10 port 26304 ssh2 However, if default INPUT policy is DROP, I got slight delay in getting password prompt after I enter username Mar 13 00:07:12 server-ubuntu sshd[6177]: Connection from 192.168.0.10 port 26333 Mar 13 00:07:35 server-ubuntu sshd[6177]: Failed none for acid from 192.168.0.10 port 26333 ssh2 For the second case, I tried to set default policy for FORWARD and OUTPUT chains to ACCEPT, but it didn't help. The only rule in this case is: -A INPUT -i eth1 -m mac --mac-source 00:26:XX:XX:XX:XX -j ACCEPT 00:26:XX:XX:XX:XX is the mac address from which I am trying to ssh to server's LAN(eth1). I'm sure there has to be some rule, which I can use while default INPUT chain policy is DENY in order to get password prompt immediately. I realize that the error message in the log is something normal and part of some verification procedure.

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• Outlook 2007 + Exchange 2010 (Save All Attachments)

  - by RobertPitt

  About 3 weeks back our company upgraded our mail system to Exchange 2010, all went smooth, few issues but nothing major. A few days ago we had a call from a colleague where he was unable to save all attachments, From File > Save As > Save All Attachments. When the email has a single attachment it works perfectly normal, and depending on the file type it allows you to save multiple attachments. But there's a lot of file types that will not work, such as zip, pdf, doc etc, Usually we get a location box open up asking where we would like to drop the attachments, but it does nothing, You click Save All Attachments and nothing happens. After hours of research I have come across mixed results, a lot of people on forums have been explaining that they have recently crossed over to Exchange 2010 and there issues started there. But on the other hand Microsoft released a KB (278188) which was depressing if that, but that article was published in 2007, as stated by the time stamp, and Exchange 2010 has only come out recently. Im looking to see if you guys have any clues what could be causing this, anything server side that I can take a look at (AD, Exchange, ...). Any help on this is greatly supported

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• Prevent Linux from processing incoming ICMP Host unreachable packets

  - by bbc

  I have a test setup with one host on a network (10.1.0.0/16) talking via TCP to another one on another network (10.2.0.0/16) and a gateway in the middle. Sometimes, the TCP connection is lost and while scanning the trace (pcap), I looks like it's because of just one ICMP Host unreachable message sent by the gateway to 10.1.0.1 at some point. 10.1.0.1 then sends a TCP RST to 10.2.0.1. In my opinion, the gateway (pfSense) is broken or not configured correctly but anyway, for testing purposes, I'd like to block this kind of ICMP on the host (10.1.0.1) before it has an influence on my TCP connection (or does it? I'm not even sure). I've tried iptables: iptables -I INPUT -i eth0 -p icmp --icmp-type host-unreachable -j DROP but while it does a good job at preventing userpace applications like ping from receiving these ICMP messages, my TCP connection still comes to an end when the alleged "killer ICMP packet" is sent by the gateway. Am I right about how it is processed? If yes, then what can I do to achieve my goal?

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• Using Windows Explorer, how to find file names starting with a dot (period), in 7 or Vista?

  - by Chris W. Rea

  I've got a MacBook laptop in the house, and when Mac OS X copies files over the network, it often brings along hidden "dot-files" with it. For instance, if I copy "SomeUtility.zip", there will also be copied a hidden ".SomeUtility.zip" file. I consider these OS X dot-files as useless turds of data as far as the rest of my network is concerned, and don't want to leave them on my Windows file server. Let's assume these dot-files will continue to happen. i.e. Think of the issue of getting OS X to stop creating those files, in the first place, to be another question altogether. Rather: How can I use Windows Explorer to find files that begin with a dot / period? I'd like to periodically search my file server and blow them away. I tried searching for files matching ".*" but that yielded – and not unexpectedly – all files and folders. Is there a way to enter more specific search criteria when searching in Windows Explorer? I'm referring to the search box that appears in the upper-right corner of an Explorer window. Please tell me there is a way to escape my query to do what I want? (Failing that, I know I can map a drive letter and drop into a cygwin prompt and use the UNIX 'find' command, but I'd prefer a shiny easy way.)

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• I've got very brazen pop3 attack how to protect the server?

  - by Ken Tang

  Today I have brazen attack to my pop3-dovecot server and mail log is full over (200MB) with this kind of information: Nov 11 09:28:14 lax dovecot: pop3-login: Aborted login (auth failed, 1 attempts): user=<shawn>, method=PLAIN, rip=200.233.152.111, lip=myip Nov 11 09:28:14 lax dovecot: pop3-login: Aborted login (auth failed, 1 attempts): user=<shop>, method=PLAIN, rip=200.233.152.111, lip=myip Nov 11 09:28:14 lax dovecot: pop3-login: Aborted login (auth failed, 1 attempts): user=<sitetest>, method=PLAIN, rip=200.233.152.111, lip=myip Nov 11 09:28:14 lax dovecot: pop3-login: Aborted login (auth failed, 1 attempts): user=<solar>, method=PLAIN, rip=200.233.152.111, lip=myip Nov 11 09:28:15 lax dovecot: pop3-login: Aborted login (auth failed, 1 attempts): user=<services>, method=PLAIN, rip=200.233.152.111, lip=myip I just blocked attacker's ip by iptables -A INPUT -s 200.233.152.111 -j DROP But it this can be continued anytime from other ips. My question is: Is there any method to disallow anyone to connect my pop3 server (except only me?) because my ip is dynamic from ISP side so I don't know how to make pop3 server know that it is exactly me connecting to. Thank you in advance!

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• Unable to Align Layers in Photoshop Properly with CS2

  - by Jonathan Sampson

  Cannot Align Semi-Transparent Items? Windows Vista, Photoshop CS2. Steps to repeat: Create new document Fill a circle on a new layer Drop opacity of filled circle to 10% Create new empty layer below circle layer Merge empty layer with filled circle layer Select entire canvas Attempt to align layers to selectionlayer > align layers to selection > vertical centers I get the following error: Could not complete the Vertical Centers command because there are no layers to be moved. Clearly this is not true, as I'm selecting the layer with the semi-translucent ball on it. Now, if you had tried this same command prior to step 5 (when the layer was at 10% opacity) it would have worked. Is there some way around this problem? I need to move layers around that begin as transparent items, with a layer opacity at 100% where 100% of the layers opacity results in showing objects that are themselves not-very opaque. I've confirmed on another machine that this problem doesn't exist in CS3. I may exist in earlier copies of Photoshop, but I only have access to CS2 (has the problem) and CS3 (does not have the problem).

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• Recommendations for good Unix MTA / groupware solutions? [closed]

  - by Jez

  Possible Duplicate: Exchange server replacement that runs on Linux I'm setting up a Debian server, and one of the things I need on it is an MTA. I don't want to use something like Exim or Postfix because I want something that ties in SMTP, POP3, and IMAP all in one (a la Microsoft Exchange). Most MTAs also seem to be hellishly difficult to configure. Try and read the Exim documentation; you could do a university degree on it (I'm not kidding). When you can get an HTTP server like Cherokee which is easy to configure and has a nice web interface, do MTAs or groupware solutions need to be that hard? I'm aware that some people think "the Unix way" is to have lots of different interacting pieces of software (like maybe an SMTP MTA, POP3 service, webmail service, and overarching manager to tie them all together), but I think this is a situation where that just makes things a lot harder to deal with and one large software suite fits in much more nicely. So, I'm looking for good open source software suites that will run on Debian that: Combine (at least) SMTP, POP3, and IMAP Are easy(ish) to configure Have a nice configuration web interface or GUI Are not defunct projects I don't mind if it's groupware and offers calendaring too, but I would only be using the e-mail functionality for now. Another nice-to-have would be built-in webmail (if we're combining a bunch of functionality, why not?) Note however that I do NOT need Outlook support. I am not really looking for an "Exchange replacement drop-in". The suites I've found so far that seem to match the above criteria (and have appropriate licenses) are Citadel, Kolab, and Zimbra. I'd appreciate anyone who has experience with any of these giving me the pros and cons of them, such as how easy they are to configure and what their performance is like. I'd also appreciate any other suggestions for solutions that fulfil my criteria that I may have missed out.

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• logfile deleted on Oracle database how to re-create it?

  - by Daniel

  for my database assignment we were looking into 'database corruption' and I was asked to delete the second redo log file which I have done with the command: rm log02a.rdo this was in the $HOME/ORADATA/u03 directory. Now I started up my database using startup pfile=$PFILE nomount then I mounted it using the command alter database mount; now when I try to open it alter database open; it gives me the error: ORA-03113: end-of-file on communication channel Process ID: 22125 Session ID: 25 Serial number: 1 I am assuming this is because the second redo log file is missing. There is still log01a.rdo, but not the one I have deleted. How can I go about recovering this now so that I can open my database again? I have looked into the database created scripts, and it specified the log02a.rdo file to be size 10M and part of group 2. If I do select group#, member from v$logfile; I get: 1 /oradata/student_db/user06/ORADATA/u03/log01a.rdo 2 /oradata/student_db/user06/ORADATA/u03/log02a.rdo 3 /oradata/student_db/user06/ORADATA/u03/log03a.rdo 4 /oradata/student_db/user06/ORADATA/u03/log04a.rdo So it is part of group 2. If I try to add the log02a.rdo file again "already part of the database". If I drop group 2 and then add it again with these commands: ALTER DATABASE ADD LOGFILE GROUP 2 ('$HOME/ORADATA/u03/log02a.rdo') SIZE 10M; Nothing. Supposedly alters the database, but it still won't start up. Any ideas what I can do to re-create this and be able to open my database again?

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• Alternative method of viewing a database diagram in SQL Server to see what tables have gone missing?

  - by Triynko

  I have a database diagram for my database, but when I open it in SQL Server, I almost immediately get a message saying some permissions changed or tables in the diagram were dropped or renamed, and tables in the diagram vanish before I can even scroll over to see what or where they were. Basically, it's saying, "Hey, you know all that time you spent laying out tables in this diagram... half of them are going to vanish when you view it, and I'm not going to tell you which tables vanished or where they were in the diagram. You're just going to see a bunch of random empty spaces where tables used to be ;)" Ridiculous. So I thought that maybe if I look in the dbo.sysdiagrams table, I could look at some plain text definition of the diagram to get a clue about the names of the tables that went missing (because thier names were probably only changed slightly) or their coordinates in the diagram (because their spatial location would give me a clue as to what they were), so that I could re-add them, but I can't, because it's a binary definition. So, is there some other program I could use to view the existing database diagram that's not going to just drop and forget the missing tables without telling me what they were, or is this information lost and at the mercy of some SSMS-proprietary database diagram format and viewer which refuses to cooperate with me.

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• Linux iptables / conntrack performance issue

  - by tim

  I have a test-setup in the lab with 4 machines: 2 old P4 machines (t1, t2) 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t3) Intel e1000 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t4) Intel e1000 to test linux firewall performance since we got bitten by a number of syn-flood attacks in the last months. All machines run Ubuntu 12.04 64bit. t1, t2, t3 are interconnected through an 1GB/s switch, t4 is connected to t3 via an extra interface. So t3 simulates the firewall, t4 is the target, t1,t2 play the attackers generating a packetstorm thorugh (192.168.4.199 is t4): hping3 -I eth1 --rand-source --syn --flood 192.168.4.199 -p 80 t4 drops all incoming packets to avoid confusion with gateways, performance issues of t4 etc. I watch the packet stats in iptraf. I have configured the firewall (t3) as follows: stock 3.2.0-31-generic #50-Ubuntu SMP kernel rhash_entries=33554432 as kernel parameter sysctl as follows: net.ipv4.ip_forward = 1 net.ipv4.route.gc_elasticity = 2 net.ipv4.route.gc_timeout = 1 net.ipv4.route.gc_interval = 5 net.ipv4.route.gc_min_interval_ms = 500 net.ipv4.route.gc_thresh = 2000000 net.ipv4.route.max_size = 20000000 (I have tweaked a lot to keep t3 running when t1+t2 are sending as many packets as possible). The result of this efforts are somewhat odd: t1+t2 manage to send each about 200k packets/s. t4 in the best case sees aroung 200k in total so half of the packets are lost. t3 is nearly unusable on console though packets are flowing through it (high numbers of soft-irqs) the route cache garbage collector is no way near to being predictable and in the default setting overwhelmed by very few packets/s (<50k packets/s) activating stateful iptables rules makes the packet rate arriving on t4 drop to around 100k packets/s, efectively losing more than 75% of the packets And this - here is my main concern - with two old P4 machines sending as many packets as they can - which means nearly everyone on the net should be capable of this. So here goes my question: Did I overlook some importand point in the config or in my test setup? Are there any alternatives for building firewall system especially on smp systems?

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• Using Truecrypt to secure mySQL database, any pitfalls?

  - by Saul

  The objective is to secure my database data from server theft, i.e. the server is at a business office location with normal premises lock and burglar alarm, but because the data is personal healthcare data I want to ensure that if the server was stolen the data would be unavailable as encrypted. I'm exploring installing mySQL on a mounted Truecrypt encrypted volume. It all works fine, and when I power off, or just cruelly pull the plug the encrypted drive disappears. This seems a load easier than encrypting data to the database, and I understand that if there is a security hole in the web app , or a user gets physical access to a plugged in server the data is compromised, but as a sanity check , is there any good reason not to do this? @James I'm thinking in a theft scenario, its not going to be powered down nicely and so is likely to crash any DB transactions running. But then if someone steals the server I'm going to need to rely on my off site backup anyway. @tomjedrz, its kind of all sensitive, individual personal and address details linked to medical referrals/records. Would be as bad in our field as losing credit card data, but means that almost everything in the database would need encryption... so figured better to run the whole DB in an encrypted partition. If encrypt data in the tables there's got to be a key somewhere on the server I'm presuming, which seems more of a risk if the box walks. At the moment the app is configured to drop a dump of data (weekly full and then deltas only hourly using rdiff) into a directory also on the Truecrypt disk. I have an off site box running WS_FTP Pro scheduled to connect by FTPs and synch down the backup, again into a Truecrypt mounted partition.

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• What differences are there between "home" switches and "professional" switches?

  - by pjreddie

  Our radio station uses a PtP wireless system to stream our radio and TV signals from our studio up a hill to our transmitter. We have been having problems with warbly sound and drop outs that come from some point in this system. An engineer that occasionally visits the station thinks it could be the switches we use on each side of the PtP wireless system to connect the PtP devices to the encoders and decoders and wants us to get two of these switches: http://www.amazon.com/Netgear-JGS516-ProSafe-16-Port-Ethernet/dp/B0002CWPOK/ref=dp_return_1 The encoder/decoder setup only streams 8Mbps total so it seems like the switches we have should not be stressed out, unless they are causing sufficient latency to degrade the performance of the encoder/decoder. At each end of the connection we only have 4 connections, is there any reason we couldn't get a cheaper, "home" quality switch like this: http://www.amazon.com/D-Link-DGS-1005G-5-Port-Gigabit-Desktop/dp/tech-data/B003X7TRWE/ref=de_a_smtd Is there a significant difference that we would notice in terms of latency between these two switches? How much does the quality of the switch actually matter in this scenario? Any help is appreciated, feel free to ask questions if anything needs clarification. Thanks

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• openvpn in a bridge?

  - by sebelk

  I have a somewhat tricky proble to solve. We have a wireless link between 2 building. One of them has an mikrotik and below there are some vlans. Some machines of one vlan need to use openvpn to connect to a remote private lan. I put a TP-Link WR1043ND (which those machines connect to) with openwrt with ebtables just in case I need it. I've configured openwrt in such a way that all ports belongs to the same vlan. My idea was to make things as transparent as I can. It has a bridge as follows: usr/sbin/brctl-full show br-lan bridge name bridge id STP enabled interfaces br-lan 8000.f8d111565716 no eth0.1 eth0.2 Also I've added an ebtables rule: ebtables -t broute -A BROUTING -p ipv4 -j DROP So "bridge" has only one IP address. I've installed openvpn and I'm trying to bring up the tunnel but I can't still get working. Sure, someone can says why don't you use the vpn on the mikrotik, there are some reasons, the first one is I have little experience with mikrotik and I'd want to have the vpn at hand :) The problem is that openvpn is not working, because it is complaining that I have only one Ip Address on the server side. So I set up and alias interface with another IP address but is not working either: : Rejected connection attempt from IP-Client-Side:37801 due to --remote setting Is there a way to make it work?

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• TCP/UDP hole punching from and to the same NAT network

  - by Luc

  I was wondering if tcp/udp hole punching would still work when you are in the same network (behind a NAT), and what the packet's path would be. What happens when using hole punching on the same network, is that it will send a packet out with the same destination and source address. Only the source and destination port would differ. I imagine a router with NAT loopback enabled will handle this as it should, but how about other routers? Would they drop the packet, or would a router (the first?) from the ISP bounce the packet back after which it gets handled okay? I'm wondering because I was thinking about using this technique to circumvent a block between peers in a network (like a school network where clients can only access the internet, but any contact with each other is blocked). The only other option is to use a man in the middle as proxy (tunnel?). The disadvantage of this is that you have to have a server with significantly more bandwidth than one that would only do hole punching. Also the latency would increase significantly.

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• Multiple copies off the same printer on Windows 7 from PrintUIEntry

  - by Kev

  I currently have a number of bat files which work perfectly fine on Windows XP which install the same printer multiple times with a number of finisher options set - e.g. after running the bat file below I would end up with four printers in the printer drop down called Sharp Kits Printer - A4 Single Sided Sharp Kits Printer - A4 Single Sided Stapled Sharp Kits Printer - A4 Duplex Stapled Sharp Kits Printer - A4 Duplex which all have there options configured in the relevant way. I have amended on Windows 7 to point to correct INF file and printer name in the INF files - a single printer installs fine. However when I run the complete batch file only the first printer in it is installed - occassionally the later ones flash up in the GUI but then vanish when you press F5 and are still missing after a reboot. SET QUEUENAME=http://192.168.7.123:631/printers/Sharp700 SET PPD=J:\DRIVERS\Printers\MX700-Win7-64\SJ1JWENG.INF SET PPDENTRYNAME=SHARP MX-M700U PPD J: cd "\DRIVERS\Printers\MX700-Win7-64" SET NICENAME="Sharp Kits Printer - A4 Single Sided" SET PREFS="J:\SCRIPTS\Printers-Win7-64bit\Sharp_SINGLE_SETTINGS.dat" %SYSTEMDRIVE%\WINDOWS\system32\rundll32.exe %SYSTEMDRIVE%\WINDOWS\system32\printui.dll,PrintUIEntry /w /b %NICENAME% /x /n "part of the n switch" /f "%PPD%" /if /r "%QUEUENAME%" /m "%PPDENTRYNAME%" rem restore settings go here... SET NICENAME="Sharp Kits Printer - A4 Duplex" SET PREFS="J:\SCRIPTS\Printers\Sharp_DUPLEX_SETTINGS.dat" %SYSTEMDRIVE%\WINDOWS\system32\rundll32.exe %SYSTEMDRIVE%\WINDOWS\system32\printui.dll,PrintUIEntry /w /b %NICENAME% /x /n "part of the n switch" /f "%PPD%" /if /r "%QUEUENAME%" /m "%PPDENTRYNAME%" rem restore settings go here... I have tried adding the "/u" paramater to the end, I have changed the "/n" paramater to be different (e.g. n1, n2,n3 etc) - both of these result in the same. I have also tried to change the port (/r) to have "_1" (etc) on the end like the GUI would but this errors as the port doesn't exist. Is it possible to do this on Windows 7, and if so how?

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• troubleshooting postifx -> exchange connection issues

  - by Systemspoet

  I have three linux-based mail routers that run postfix and relay mail to our on-premise exchange server as well as to outlook.com, splitting the mail based on ldap atttributes. What I've observed sporadically since upgrading this spring from Exchange 2007 to 2010 is that all three of the mail relays will, for about 20 minutes, fail to connect to exchange. Postfix logs it as "lost connection with exchange.contosso.edu" ; this problem almost always occurs to all three mail relays at the same time, and lasts for slightly under 20 minutes. If I can catch it while it's occuring, and I manually do "telnet exchange.contosso.edu 25" from one mail relay and force a message through (helo, mail from, rcpt to, data, etc), then it clears that relay up. The exchange "server" is actually two machines with the HT role on them, load balanced via windows NLB. I've worked pretty hard to figure out what's happening from the postfix side and I can't see any evidence of any misbehavior. My question is, how do I attack the problem from the exchange side? Is there a connection log, or a debug setting, or something I can do to log all of the inbound connections and tell me what's causing exchange to drop them?

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