zizzencs - Developer IT

Using PAM and vsftpd without root access

- by Zizzencs

I'm trying to set up a few vsftpd instances on a machine that I have no root access to. The authentication should be done through PAM with pam_listfile, like this: pam_listfile.so item=group sense=allow file=/path/filename onerr=fail I can ask the administrator to set up a PAM service for me and include that line but he is not willing to create 6 PAM services for my 6 vsftpd instances and I really need different /path/filename set for each vsftpd server. Is there a way to solve this problem? Can I somehow not use absolute path as the parameter? (I know the correct solution would be to use one vsftpd instance and set up virtual users properly. However unfortunately I have to work what I have and the users already exist in an Active Directory and are authenticated to the system using another PAM service.)

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Choose relayhost based on the postfix smtpd instance

- by Zizzencs

I'd like to setup a postfix host (using RHEL 5.4's default postfix, which is version 2.3) with the following characteristics: an SMTP listener listens on 10.0.0.1:25 and relays all e-mails to 10.0.0.1:2525 an SMTP listener listens on 10.0.0.1:2525 and relays all e-mails to 10.0.0.2:25 Basically the challenge here is to use two different relayhosts for the different SMTP listeners. Is it possible? Is there a better solution to achieve similar behavior?

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Copying files between linux machines with strong authentication but without encryption

- by Zizzencs

I'm looking for a suitable program to copy files from one linux machine to another one. The program should be able to do authentication but it should not do encryption. The reason behind the latter is the lack of CPU power to do the encryption. I copy backups from ~70 machines to a single backup server simultaneously. The single server is an HP Proliant DL360 G7, with 10 Gbps ethernet connection and an FC storage backend that can do 4 Gbps. Through FTP I can write ~400MB/sec to the storage (that's about what I want) but through ssh with arcfour I can only do ~100MB/sec while having 100% CPU usage. That's why I want file transfers not to be encrypted. The alternatives that I found not really suitable: rcp: no authentication, forget it FTP: making the authentication "secure" (at least preventing plain-text password exchange) is possible but not really easy and I haven't found a method to force any FTP daemon to encrypt the control channel (for the authentication) and not to encrypt the data channel (for data transfers) SCP/SFTP: in farely recent ssh(d) implementations you can't turn off encryption. The best you can do is to use the arcfour cypher for the encryption but it sill uses too much CPU power for my needs. rsync over ssh: same problems as with SCP/SFTP. plain rsync: from the documentation of rsyncd: "The authentication protocol used in rsync is a 128 bit MD4 based challenge response system. This is fairly weak protection, though (with at least one brute-force hash-finding algorithm publicly available), so if you want really top-quality security, then I recommend that you run rsync over ssh." It's a no-go. Is there a protocol/program that can do exactly what I want? (A big plus would be if it could work on windows as well and/or if it would support rsync-stlye copying/synchronization (e.g. copy only the differences).)

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How to handle knowledge handover effectively?

- by Zizzencs

Let's say a large enterprise opens a new office in (insert random location here) and want the new colleges up to speed as fast as possible. Let's also say this enterprise is a very typical one with a complex environment, lots of history and almost full lack of documentation. What's already been decided is that the new colleges will receive howto-style documentation for the most typical tasks and will get seme architecture documentation for some of the more complicated systems. Any ideas about improving this process? And more specifically, how should such a howto document look like to be helpful?

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Home router for higher network loads

- by Zizzencs

I'm trying to find a replacement for my ASUS WL500GP router. Some constraints: my ISP now provides 120 Mbit bandwidth - the router must be able to handle it I have 3 computers and a laptop at home - the router must have at least 4 LAN ports and the WAN port I need to be able to do the following in parallel: use bittorrent with ~1000 connections transfer files from one home computer to another at high speed access one home computer from my workplace I don't really need wireless I don't really want two boxes to serve all these purposes. So I was searching for a router with 1 Gbit ports, jumbo frame support and good reviews, but haven't really found a promising candidate so far. Any suggestions?

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Aborting upload from a servlet

- by Zizzencs

I'd like to limit the size of the file that can be uploaded to an application. To achieve this, I'd like to abort the upload process from the server side when the size of the file being uploaded exceeds a limit. Is there a way to abort an upload process from the server side without waiting the HTTP request to finish?

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Using a set of numbers inside a database without creating a temporary table

- by Zizzencs

I have a set of numbers and a table in a database with the id (primary key) and text (not null) columns. I would like to create a query that returns all the numbers in the set and the associated text from the table. Unfortunately not all numbers exist in the database's id column, so this won't work: select id, text from table where id in (<set of numbers>) For the non-existing ids the best would be to return null as the text from the query. Is there a way to produce the desired output without first creating a temporary table from the set inside the database? The database engine in use is a Microsoft SQL Server 2008 SP1 but I'd be interested in any solution with any database engine.

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