Discuss August 2008

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271 participants
280 discussions

[OT] VPN/DMZ best practices
by Scott McClanahan 14 Aug '08

14 Aug '08

There is such a wealth of knowledge and personal experience on this list that I'd like to get your opinions on our current situation. Currently, we have a simple tri-homed firewall with the internal network on one interface, the dmz on another, and the dirty internet on the last. Also, there is a spare interface on the box which is unused. We use CentOS and manually maintain our rule sets and routes since it's not really that complex. I'd like to setup a vpn connection between our office and a remote office, as well as, allow remote users to vpn into there desktops and map samba shares. I would prefer to tie in the openvpn software with our internal openldap server. Our dmz is currently not in use at all but will be soon, hosting our software. Having said all of this, what insights do you have for the following: 1. What are your recommendations for where the vpn (openvpn on linux) appliance should reside? In the dmz? Internally and configure the firewall to allow (and nat) vpn connections? On the unused interface in a different dmz than our hosting software? Somewhere else? 2. Should I abandon the single firewall approach and instead use two firewalls in a more traditional setup (gateway firewall -> dmz -> internal firewall)? If so, where should the vpn appliance go? I'll probably have more questions based on your answers and I look forward to the responses. Thanks.

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Firewall/Proxy with time window access control
by Lunix1618 14 Aug '08

14 Aug '08

Hello all, I have to setup a system that required to block users access internet in work time but let them access internet on specified time window e.g lunch time. I plan to use iptables and squid to do block and web caching but I have no idea how to control access on time frame. Could any one of you experienced with this can give some starting point /document/howto start reading ? My firewal/proxy box will be CentOS 5.2 so I prefer something that can install via yum/rpm Thanks in advance!

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NFS not syncing until directory viewed.
by andylockran 14 Aug '08

14 Aug '08

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Guys, Having a weird problem with NFS. We have two web-servers under a load balanced system. Web1 and Web2. Currently all files are hosted in Web1, and we use NFS exports to share the files with Web2. Up until recently this was working fine (two/three weeks ago). However, it's starting to behave a little randomly. When a file is uploaded, it appears on Web1, yet is not accessible when browsing the Web2 server. Weirdly though, when I log into the Web2 server to check if it's there, it does appear there with correct timestamp et al.. The funny thing is, that after I check it's on Web2.. it then starts to work thorough the browser. So simply logging in and checking it's there must give it a kick of some sort. If anyone else can give me advice on how to resolve this, it would be much appreciated. Regards, Andy -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFIpAx8auMjEM4rxIQRAuPQAJ41JGA98CIbP8hFIVhVma50mXQOzgCgiZVa ilBmX+CY1ZChtUVvZqP45mY= =9N4b -----END PGP SIGNATURE-----

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What is vibr0 Network interface and what is it used for
by Lunix1618 14 Aug '08

14 Aug '08

Hello, I have see that my machine have an interface that named virbr0. I have no idea what is it and what it using for ? I am not configured any IP address for it but I see it had an IP address and see it listed in firewall config. Can anyone give me an explanation about this or point me to a document that describe it ? My machine running CentOS 5.2 and do not have internet connection from the installation time. Thanks, virbr0 Link encap:Ethernet HWaddr 00:00:00:00:00:00 inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0 inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:35 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:9143 (8.9 KiB)

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how to create whole image
by kapil singh 13 Aug '08

13 Aug '08

Hello, I am using Cent OS 5.2 . i want to create one master image of whole running OS becoz i have to do same installation many times on different machines. so any one suggest me to how create and run the image of whole OS at the time of installation or , which escape me to install each and every thing many times. i would not like to create image using dd. any suggestions ?? - - Thanks and Regards Kapil Singh Kushwah Linux System/Network Administrator Hotwax Media Inc. Indore,(M.P) INDIA

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Boot from degraded sw RAID 1
by Eduardo Grosclaude 13 Aug '08

13 Aug '08

OK, this is probably long, and your answer will surely make me slap my forehead really hard... please help me understand what goes on. I intend to install CentOS 5.1 afresh over software RAID level 1. SATA drives are in AHCI mode. I follow basically [1] though I have made some mistakes as will be explained. AFAIK GRUB does not boot off LVM, so I: 1. Build a 100MB RAID-type partition on each disk 2. Build a second RAID-type partition taking the remaining space on each disk 3. Build a RAID 1 device over the small partitions 4. Build a second RAID 1 device over the bigger ones 5. Declare /boot as ext3 to live on the smaller RAID 1 device 6. Declare an LVM PV to live on the bigger one 7. Build a VG on the PV, then build LVs for swap, / and /data on the VG Only problem is, I numbly have failed to follow [1] in that I left Disk Druid to make partitions wherever it chooses, so now I have cross-named partitions... md0 is the bigger RAID 1 device with /dev/sda2 AND /dev/sdb1... and md1 is the smaller one with /dev/sda1 AND /dev/sdb2. Oh well, things can't get complicated on this, I tell myself. Installation goes on well, system boots. I update the system. Now I want to be able to boot from whichever disk survives an accident. If I take out sdb, system boots. If I take out sda, system refuses to work. Aha. GRUB is not installed into sdb's MBR. Reconnect sda, reboot. Prepare for GRUB device juggling as in [1]. Into GRUB console I do > find /grub/stage1 hd(0,0) hd(1,1) > device (hd0) /dev/sdb > root (hd0,1) Filesystem type is ext2fs, partition type 0xfd > setup (hd0) Checking if "/boot/grub/stage1" exists... no Checking if "/grub/stage1" exists... yes Checking if "/grub/stage2" exists... yes Checking if "/grub/e2fs_stage1_5" exists... yes Running "embed /grub/e2fs_stage1_5 (hd0)"... 15 sectors are embedded. succeeded Running "install /grub/stage1 (hd0) (hd0)1+15 p (hd0,1)/grub/stage2 /grub/grub .conf"... succeeded Done. > quit The rationale for this being that, when the faulty disk is removed at boot, the remaining one (currently /dev/sdb) will be addressed as /dev/sda (i.e. hd0 in GRUB parlance). Now I prune /dev/sda and reboot. I see: root(hd0,0) <----------------------------------------------- interesting Filesystem type unknown, partition type 0xfd kernel /vmlinuz-2.6........ ro root=/dev/VolGroup00/LogVol01 rhgb quiet Error 17: Cannot mount selected partition Press any key to continue... Not quite what I expected. I enter GRUB console at boot and repeat the above device juggling. > find /grub/stage1 hd(0,1) > root (hd0,1) > setup (hd0) > quit However, 'quit' seems to fail as grub keeps prompting me without really quitting. After a forced reboot I get the very same error message as above. I edit the GRUB configuration entry at boot (with e command) and see root (hd0,0) as the first line It should be root(hd0,1), so probably GRUB did not write down my modifications. I edit it to read so (e command again), and then boot (b command). Now it works. I rebuild the arrays succesfully. However, I have made a one-time edit and the problem is still there. I understand the error message from the booting process was reasonable: hd(0,0) carries an unknown filesystem -- an LVM device. [1] was right, you definitely want to have exact disk duplicates to keep your life simple. However, I can't see why it shouldn't work the way it is. I can probably rebuild the secondary disk to mimic the primary's partition numbering and "fix" my problem... But, Am I right about the GRUB console commands I was issuing? How can I make them permanent then? I KNOW I did 'quit' from the grub console the first time, when from inside bash, when the system was running. What am I missing? Thank you in advance [1] http://lists.us.dell.com/pipermail/linux-poweredge/2003-July/008898.html -- Eduardo Grosclaude Universidad Nacional del Comahue Neuquen, Argentina

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vncserver on IPv6
by Robert Moskowitz 13 Aug '08

13 Aug '08

http://www.realvnc.com/products/enterprise/4.1/ipv6.html IPv6 support in VNC Server E4.1.7/P4.1.2 VNC Server E4.1.7 & P4.1.2 are fully IPv6-aware, but is shipped with IPv6 support disabled by default, for security reasons. IPv6 can be enabled by setting "InTransports=IPv6,IPv4" (the default being IPv4 only), either on the command-line when starting vncserver under Unix Ok. we have vnc-server-4.1.2-9.el5.i386.rpm, so it SHOULD support IPv6. Don't know how to add a setting to the command-line, as I rund VNCserver via the service command, but I added it to /etc/sysconfig/vncservers: InTransports="IPv6" (note I also tried without the quotes) and netstat -na|grep 5902 shows vncserver only running on IPv4 and I can only connect to it via IPv4. So what am I missing?????

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udev rules for /dev/sd[a-z] ?
by James Pearson 13 Aug '08

13 Aug '08

I have a third party application that I want to run a CentOS4 box that is expecting to access the generic SCSI devices through /dev/sga, /dev/sgb, etc. However, the devices set up by udev are /dev/sg0, /dev/sg1 etc. Does anyone know what syntax I could use to create a udev rule that creates symlinks sga -> sg0 etc. for each sg[0-N] device? Thanks James Pearson

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support libipq?
by Mike -- EMAIL IGNORED 13 Aug '08

13 Aug '08

I am thinking of trying centos (I am now using Fedora). Does centos support libipq? Thanks, Mike.

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Re: Boot from degraded sw RAID 1 SOLVED
by Eduardo Grosclaude 13 Aug '08

13 Aug '08

On Wed, Aug 13, 2008 at 3:07 PM, Eduardo Grosclaude <eduardo.grosclaude(a)gmail.com> wrote: > OK, this is probably long, and your answer will surely make me slap my > forehead really hard... please help me understand what goes on. <autoslap>Ouch!</autoslap> Sure /boot/grub/grub.conf still needs editing... That's why you really, really WANT both partition tables to be identical... -- Eduardo Grosclaude Universidad Nacional del Comahue Neuquen, Argentina

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Discuss August 2008