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10372 discussions

Pinging Server's 127.*.*.* subnet
by steve-ALUG＠hst.me.uk 25 Jul '11

25 Jul '11

Hi all, I was trying to add a extra IP address to my server's localhost because I wanted to run a apache virtual host on a separate IP address. I used sudo ip addr add 127.0.0.5/32 dev lo and then I could ping 127.0.0.5 successfully. When I'd finished, I ran sudo ip addr del 127.0.0.5/32 dev lo which didn't return any error messages. I than ran ping 127.0.0.5 and still got responses. I ran sudo ip addr del 127.0.0.5/32 dev lo again and it told me that it could not do it "RTNETLINK answers: Cannot assign requested address" It may be that the ip addr add has nothing to do with it, but on this machine, my server, I can ping any address I've tried in the 127.*.*.* range and get a response. Is this normal, or have I messed something up? If so, what have I messed up? Is there anything I can run that show's what's providing these ports? It's an Ubuntu machine, running dnsmasq, apache. Ubuntu 10.04.3 LTS Any ideas? Or am I being thick??? Steve

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Network delay issue
by Stuart Bailey 22 Jul '11

22 Jul '11

I have a mid sized network, around 80 users. Most of these users are using windows clients, with a few macs. There are 3 Linux servers, 2 for file services (samba and netatalk), and one as domain controller (Samba) and email (cyrus / postfix). There is also a windows server used for Sage. We have recently started to notice periodic delays in network traffic. I am not aware of any changes to the network at the time when this problem started - it has been fine for 18 months or so. This has been noticed as follows: 1. remote ssh into Linux server - typing gets momentarily delayed, for about 5-10 seconds, then resumes. This occurs randomly, but typically every minute or so. 2. Remote desktop (to a windows client), freezes, and occasionally drops out. 3. File access to samba shares sometimes takes a very long time, or times out. Then a retry works almost instantly. 4. There is also a DOS (runs in XP command window) based database, whose files reside on a samba share. When scrolling through records, this occasionally freezes, then resumes. The delay periods are all fairly consistent - ie, they affect the above for roughly the same periods. I have monitored tcpdump from the Linux server whilst accessing the database, and can see server responses from samba to the DOS client, immediately before a delay occurs. I am certain the servers are not responsible, since it affects services on different machines, and can see samba packets from the server at the right time. Also, I've monitored the broadband traffic, and can see nothing unusual. The network has gigabit connections from the servers to 3 stacked switches. Fibre between buildings - although the problem affects all buildings. Clients are typically on 100M connections. the windows clients are all running NOD32 AV. RKhunter and chkrootkit are run on the servers overnight, and show nothing. I'm not sure what else to look for. I've monitored the servers with wireshark, and they look normal. Any ideas would be welcome, please. Stuart Bailey BSc (hons) CEng CITP MBCS LinuSoft (Managing Director) Linux Specialist & Software Developer ~~~~~~~~~~~~~~~~~~~~~~~ Phone: (0845) 658 3563 Direct: +44 (0) 1953 878162 Fax: +44 (0) 1603 858583 ~~~~~~~~~~~~~~~~~~~~~~~ http://www.linusoft.co.uk __________ Information from ESET Mail Security, version of virus signature database 6308 (20110719) __________ The message was checked by ESET Mail Security. http://www.eset.com

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SSH keys
by Mark Rogers 21 Jul '11

21 Jul '11

I have a remote server that I want to allow SSH access to but only to certain people, and I don't trust passwords, so keys are the way to go. However, all I know about setting up keys is based on the user creating a public/private key pair, and the server adding that user's public key to it's trusted keys to allow access. Ideally what I want to do is the other way around, in that I want to generate the key pairs on the server and copy the relevant key to the clients so that they all share the same key (there won't be many users and I just want to give them a key rather than have them create keys themselves). What is the "correct" way to do this, or am I doing something horribly wrong? I figure that I can set up the key pair myself as usual, but then copy the private key from my PC to anyone else who needs access, but I'm not sure if that's the right approach. (I'm quite OK with the idea of creating different keys for different users, adding them to the server, then issuing the keys to the users, so I can revoke access from any given user quite easily if I need to; I just don't want the users having to do the key creation bit.) If it's relevant, most of the users other than me will be connecting via Windows (PuTTY), and will need to be able to tunnel through the SSH connection for various apps. -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) @ 13 Clarke Rd, Milton Keynes, MK1 1LG

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CSS/HTML question - how to vary a CSS value easily?
by Chris G 20 Jul '11

20 Jul '11

I have done a Google search for 'dynamic CSS' and I can see large scale ways of doing what I want to do but I was wondering if anyone has a simple way of doing it. What I want is a way to insert a variable amount of vertical space between blocks of HTML. The particular case I'm interested in is where I have a <UL> below either a <P>...</P> or below a heading <Hx>. The problem is that the HTML is generated by a Wiki so one doesn't have *direct* access to the generated code and the text above a list is *always* a paragraph, it's not possible to turn it off. The existing CSS setting margins for paragraphs and headings works right for 99% of cases but when you have lists under heading *and* lists under paragraphs it's very difficult to get things right using just the CSS. So, a quick (and dirty?!) approach to fixing the few places where the spacing is too small or too large would be to have the ability to insert an empty block/paragraph where one could set the height/margins easily. A quick, single case, bodge is something like:- <DIV id=unvert><P></P></DIV> With CSS for div#unvert setting appropriate size/margins. However what I'd *really* like to do would be to enable setting of the margins or height of the paragraph from the code somehow, that would allow one to insert more/less space as required rather than needing lots of different CSS ids, one for each different spacing. Any ideas, or completely different approaches, or am I missing something entirely? -- Chris Green

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Surprised at different 'rm -f' operation when root or not root work?
by Chris G 20 Jul '11

20 Jul '11

I have just discovered that 'rm -f' (also 'rm -fr') only overrides permissions when run as root. I.e. if I have a file I own that is read only I *can't* delete it if I am the user that owns the file, even using 'rm -f', however if I sudo to root privileges then 'rm -f' will remove the file even if there is no write permission. Strangely the man pages on my system don't seem to document this difference between root and non-root use of rm. For the -f option it just says:- `-f' `--force' Ignore nonexistent files and never prompt the user. Ignore any previous `--interactive' (`-i') option. Which seems to be the non-root case, i.e. it *doesn't* remove a file where you don't have write permission even with '-f'. So where is the 'do it regardless of permissions' action which happens when root uses 'rm -f' documented? Finally, the thing that caused the problem, how do I guarantee that an 'rm -fr' run by a user will be able to delete everything in the specified directory tree? Do I have to do a 'chmod -R +w' first? -- Chris Green

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Scripting question - how to get *relative* directory within a bash script?
by Chris G 19 Jul '11

19 Jul '11

I need to find what the relative directory (relative to $HOME that is) within a bash script and, at the moment, I can only see rather messy ways of doing it. To go into more detail I want a way to generate a string of the form ~/subdir1/subdir2 when a script is run from ~/subdir1/subdir2. The best I can come up with at the moment is to get the full path to the current directory using pwd and then to remove $HOME from that string using sed, e.g.:- fullpath=`pwd` relpath=`echo $fullpath | sed s#$HOME#~#` Actually that's not quite as nasty a I thought, but it still feels like there should be a neater way. (I haven't tried it so there may well be issues with quoting etc. but you can see the idea) Any ideas? -- Chris Green

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[ALUG Announce] 3rd Monday Monthly Ipswich Social Meeting : McGintys, Northgate Street
by samwise 18 Jul '11

18 Jul '11

ALUG Announce Please send announcements to Announce(a)lists.alug.org.uk Unsub, change settings via http://lists.alug.org.uk/mailman/listinfo/announce ----- After an inexplicable absence in June, the monthly "Third Monday" ALUG Ipswich Social Meeting is back tonight, Monday 18th July, at 20:00: P J McGinty & Sons 15 Northgate Street Ipswich Suffolk IP1 3BY Tel: 01473 251 515 Map/Directions URI: http://maps.google.co.uk/?q=IP1+3BY WWW: http://www.pjmcgintys.co.uk/ McGintys pub is in the centre of Ipswich. It's directly opposite the town's central library and has a reputation for good Irish beer. We're usually to be found in the lowest section of the bar, near the library entrance to the pub. All are welcome, novices and experienced users. Feel free to ask for further information on the Main ALUG mailing list. I'll definitely be there, so if any one new wants to drop in, look for the guy in the corner with the latest copy of LXF ... ;) We're normally in the downstairs-from-the-bar-bit, nearest the entrance on the library side. Peter. ----- Send discussion replies to main(a)lists.alug.org.uk (Reply-To set) Unsub, change settings via http://lists.alug.org.uk/mailman/listinfo/announce

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Installing Ununtu server to degraded RAID
by Mark Rogers 13 Jul '11

13 Jul '11

I want to set up a server using software RAID1 as follows: - Install single disk, do the OS install (Ubuntu server 11.04), creating RAID array (but degraded as only one disk) - Boot the system and check it all works - Install second disk and add to array The install works fine (I create an md partition and an array of 2 devices but only add one to it), and install grub to /dev/sda1 as usual. However it won't boot. Grub starts and gives me my menu, but gets no further. Suggestions? Am I doing this all wrong? (Reason for doing this: migrating an existing RAID1 array using the onboard RAID to an mdraid array; I want to keep one of the original disks to recover some files off once the system is up before wiping it and adding it to the new array. But also I want to confirm that my new array will boot with only one disk otherwise there's not a lot of point to it!) -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) 21 Drakes Mews, Milton Keynes, MK8 0ER

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[ALUG Announce] ALUG Norwich Pub Meet Thursday 14th July
by Viperfang 11 Jul '11

11 Jul '11

ALUG Announce Please send announcements to Announce(a)lists.alug.org.uk Unsub, change settings via http://lists.alug.org.uk/mailman/listinfo/announce ----- Hello Aluggers, Our monthly ALUG Norwich social meeting will be held this Thursday, 14th July at The Coach and Horses (82 Thorpe Road, Norwich, NR1 1BA). The meeting officially starts at 8pm, although some people may arrive earlier. More information on those people can be found on the list and the IRC channel. If you are unsure if you will recognise us then make yourself and your intent to attend known by either posting on list or visiting us on IRC so we can look out for you rather than hiding in the corner. Optionally you could ask at the bar if they know where the geeky computer weirdos are and they'll point you in the right direction (seriously!). Another possibility is look for heaps of electronics on a table that may possibly look like movie props that would used for detonating explosives. Feel free to bring electronics/laptops/gadgets to the meet, you will by no means be alone. Ben Bewick aka Viperfang NB: This mail is automated, please refer to the usual sources for more information. ALUG Contact Details: Website : http://www.alug.org.uk/ IRC : #alug on irc.alug.org.uk List : http://lists.alug.org.uk/mailman/listinfo Twitter : http://twitter.com/anglianlug Identica: TBA Facebook: http://www.facebook.com/group.php?gid=2381613902 ----- Send discussion replies to main(a)lists.alug.org.uk (Reply-To set) Unsub, change settings via http://lists.alug.org.uk/mailman/listinfo/announce

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Reg Exp question
by Stuart Bailey 08 Jul '11

08 Jul '11

Hello, I'm trying to search for a file name by pattern that will output the full path and timestamps. I've tried using ls -Rl | grep "^\." to show all the directories. but then I need to show all files within those directories that match my pattern, eg *abc.png Can I do this with my reg exp? Find does not give the timestamps. Many thanks, Stuart Bailey BSc (hons) CEng CITP MBCS LinuSoft (Managing Director) Linux Specialist & Software Developer ~~~~~~~~~~~~~~~~~~~~~~~ Phone: (0845) 658 3563 Direct: +44 (0) 1953 878162 Fax: +44 (0) 1603 858583 ~~~~~~~~~~~~~~~~~~~~~~~ http://www.linusoft.co.uk __________ Information from ESET Mail Security, version of virus signature database 6276 (20110708) __________ The message was checked by ESET Mail Security. http://www.eset.com

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