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  • Centos 6 vsftp server

    - by henry
    I have installed vsftpd server in my centos 6 server. I created three users.first user can access the ftp server using his system password.All the users are in chroot_list. when the second user is trying to access through ftp with his password, one error message as follows: "operation not supported " my server's selinux configuration: [henry@admin ~]$ getsebool -a | grep ftp allow_ftpd_anon_write --> off allow_ftpd_full_access --> off allow_ftpd_use_cifs --> off allow_ftpd_use_nfs --> off ftp_home_dir --> on ftpd_connect_db --> off httpd_enable_ftp_server --> off sftpd_anon_write --> off sftpd_enable_homedirs --> off sftpd_full_access --> off sftpd_write_ssh_home --> off tftp_anon_write --> off How can I troubleshoot this issue?

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  • network topology including many services

    - by mete
    I know this is yet another question on how to setup network but I hope you are not bored of such questions yet. The site is also an office, so it includes windows dc, windows ad, exchange, sql, file sharing, development app servers and other pcs. In addition to office (internal) things, there are both test and prod environments consisting of a web server-app server-sql stack. There is also ftp service open to public. I consider: dmz1 - web server - exchange edge - ftp dmz2 - app server - sql for app server internal - dc and ad - exchange hub and transport - internal file sharing - sql for internal use - app servers for internal use - pcs public - dmz1, only web, ftp and smtp public - dmz2 not possible public - internal not possible dmz1 - dmz2 is possible from web servers to app servers by using http or ajp dmz1 - internal is only possible for exchange, otherwise not possible dmz2 - internal not possible Does this sound ok ? Any other recommendations ? It will be configured using either MS ISA or Jupiter SSG. Thank you.

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  • Where can I find old versions of linksys router firmware?

    - by Doug T.
    Hello everyone, I've had a headache of a weekend after upgrading to the latest firmware for my wrt54g. Suffice it to say I'm not satisfied with the latest version. Now I'm looking around for the previous version of the firmware out there on the interwebs and am having trouble. I noticed that linksys at one point had an ftp site: ftp://ftp.linksys.com. There you could find old firmware for your device. It now appears defunct. Does anyone know where I could find old firmware versions for my wrt54g router?

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  • VSFTPD uploaded file permissions

    - by Katafalkas
    Let me first say that there are loads of topics regarding this, and I am sure i have seen them all by now. Still non of the solutions seem to help. I installed vsftpd. created a user ftp-data. Now I need that files uploaded by user ftp-data would have 755 permissions. Solving this should be as easy as adding: local_umask=002 file_open_mode=0755 but that did not help, then I have tried a number of variations of this, still did not help. The I added: chmod_enable=YES still did not help. At the moment I think that I am missing something very simple and obvious, just cant find it. Maybe someone could help me to find what I am missing. This is my config file: anonymous_enable=NO local_enable=YES write_enable=YES local_umask=002 anon_upload_enable=NO anon_mkdir_write_enable=NO dirmessage_enable=NO xferlog_enable=YES connect_from_port_20=YES xferlog_file=/var/log/xferlog listen=YES local_root=/var/www/ftp-gallery pam_service_name=vsftpd userlist_enable=YES tcp_wrappers=YES

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  • iptables and snatting to different networks

    - by codingfreak
    linuxbox (p.q.r.t) | | INTERNAL ------ ABCD ----- INTERNET (p.q.r.s) (m.n.o.k) ABCD has 3 interfaces connected to linuxbox, INTERNAL N/W, INTERNET. Linuxbox has a private address (p.q.r.t). At present I am snatting the packets from linuxbox to INTERNET at ABCD. I have a small doubt regarding the FTP from linuxbox since I have to support ftp from linuxbox to both INTERNAL N/W as well as in INTERNET. How can I right a rule in iptables present in ABCD where it can decide if the destination ip-address of ftp server is within INTERNAL N/W or in INTERNET and do natting accordingly.

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  • vsFTPd and iptables - how to configure them in CentOS 5.5?

    - by Vincenzo
    I've installed vsFTPd in CentOS 5.5, on TWO servers, and added this rule to their iptable-s: -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 21 -j ACCEPT Looks like this is not enough, since when I'm trying to upload a file from one server to another, I'm getting this result (IP address is masked): # ftp 99.99.99.99 Connected to …com (99.99.99.99). 220 (vsFTPd 2.0.5) Name (99.99.99.99:root): vinny 331 Please specify the password. Password: 230 Login successful. Remote system type is UNIX. Using binary mode to transfer files. ftp> ls 227 Entering Passive Mode (99,99,99,99,107,74) ftp: connect: No route to host I've found a few articles in the net about the second rule I have to add to iptables, but I didn't find the right syntax for it. Could you please help?

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  • How can I switch Linux running OS from disk to running from RAM without restarting?

    - by vfclists
    Is it possible to switch to running Linux from RAM or RAM disk after starting starting initially from disk? eg. You need to make an image of your hard disk, FTP it to a remote location, some time later you want the image back, so you start the system from disk as usual, restore the image you FTP'd from the remote location back into place. More like a CloneZilla backup and restore, without booting the server from CD or USB disk, but starting from the normal hard disk? Notes on environment I should have mentioned it earlier. It is a remotely hosted VM where I cannot boot into a recovery console mode or do a netinstall. It will always boot onto the same disk. Which means that if there is some serious corruption I can't repair it offline, which is why being able to ftp a previously saved backup into place is so important

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  • SSH: one user logs in, other don't

    - by Co Lega
    Some users can ssh correctly, others don't. I have an admin user, which is in wheel. I used vsftpd for allowing FTP. I created a nologin user for FTP. Call this user "ftpuser". Now I want to allow sftp. It allows me to connect using admin user. I remove the nologin, by giving the user a shell via usermod -s /bin/bash ftpuser. It still doesn't allow me to connect from the ftpuser via sftp. The content of /home/ftpuser/.ssh is just the known_hosts file which contains "localhost" entry only. User permissions are (in theory) ok: ls -la /home working (admin) : drwx------ 18 admin admin 4096 Feb 6 15:33 admin non-working(ftpuser): drwx------ 3 ftpuser ftp 4096 Mar 26 15:25 ftpuser I haven't configured anything special on openssh. Does the ftpuser need anything extra than shell to enter via ssh?

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  • How to test Laptop NIC's throughput using a router and PC - without be bounded?

    - by 0x90
    My setup includes: Cisco router An i-7 PC running windows A laptop with high speed wifi nic, which I want to check its throughput. I would like to run an FTP server on the PC. hook the router over cables to the PC. I would like to have the PC create its own subnet accessible via the cisco router that would be hooked directly to the PC's nic. From the laptop I want to connect via wifi to the PC's wireless router and connect to the ftp server on the PC. is it possible? how do i connect the router to the PC nic and make it broadcast a subnet via wifi for my laptop to connect to? how do i configure an FTP server to operate only on this subnet?

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  • proxy server software for windows xp

    - by This is it
    Hi Is there a proxy software for Windows XP that can support HTTP, HTTPS, SMTP, IMAP, POP, FTP, etc. (the more the better)? We tried apache mod_proxy but FTP doesn't work through it (at least not all features). Maybe we don't need proxy server for following requirements (we are open for suggestions): - Centralized access point to internet for several users (proxy server?) - Users use Browser (firefox/IE - HTTP, HTTPS), Outlook (SMTP, POP, IMAP) - Logs to see where did users go on internet - Possiblity to connect to FTP server Windows xp, which is used as proxy server, is a virtual machine, and all other users/clients are virtual machines as well (Hyper-V)... Thanks for suggestions. Cheers

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  • How do I restore a backup of my keyring (containing ssh key passprases, nautilus remote filesystem passwords and wifi passwords)?

    - by con-f-use
    I changed the disk on my laptop and installed Ubuntu on the new disk. Old disk had 12.04 upgraded to 12.10 on it. Now I want to copy my old keyring with WiFi passwords, ftp passwords for nautilus and ssh key passphrases. I have the whole data from the old disk available (is now a USB disk and I did not delete the old data yet or do anything with it - I could still put it in the laptop and boot from it like nothing happend). The old methods of just copying ~/.gconf/... and ~/.gnome2/keyrings won't work. Did I miss something? 1. Edit: I figure one needs to copy files not located in the users home directory as well. I copied the whole old /home/confus (which is my home directory) to the fresh install to no effect. That whole copy is now reverted to the fresh install's home directory, so my /home/confus is as it was the after fresh install. 2. Edit: The folder /etc/NetworkManager/system-connections seems to be the place for WiFi passwords. Could be that /usr/share/keyrings is important as well for ssh keys - that's the only sensible thing that a search came up with: find /usr/ -name "*keyring* 3. Edit: Still no ssh and ftp passwords from the keyring. What I did: Convert old hard drive to usb drive Put new drive in the laptop and installed fresh version of 12.10 there Booted from old hdd via USB and copied its /etc/NetwrokManager/system-connections, ~/.gconf/ and ~/.gnome2/keyrings, ~/.ssh over to the new disk. Confirmed that all keys on the old install work Booted from new disk Result: No passphrase for ssh keys, no ftp passwords in keyring. At least the WiFi passwords are migrated.

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  • Cannot access personal website from home IP. More details inside.

    - by GX67
    This is a recent problem I've been having. My site can be accessed from almost everywhere else except from my home IP, where I do most of my editing/updating, etc. I've tested my connection from my school's network, a friend's connection from out of state (multiple states), and through a tethered connection with my friend's Android. It works in all those cases, both viewing, accessing the cPanel, and using FTP. Here's the problem that happens to me when I try to view it from my home IP: The page times out in Firefox, IE, and Chrome. Using the cmd, I ran tracert and ping, both as failed attempts. Log here. downforeveryoneorjustme.com says my site is up. So do the other site checkers. I can't access my cPanel or FTP accounts. I can't access the host site. (I use perfectz.info for hosting, and I can't access their site either.) System settings: No firewall enabled. Ports are seemingly properly forwarded. (e.g. The ports are open in the router settings, and are open everywhere else.) I have an email forwarder set up from the cPanel that works just fine. (i.e. I can receive emails sent to that address. If any other information is needed, I'll do my best to provide it. UPDATE @ilhan: I use two things: 1) The site cPanel from in-browser. 2) Dreamweaver CS5 FTP. @Matthias: I tested both, and it passes the dual stack with a 10/10. What should I do then?

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  • Ditch cPanel / WHM in favour of manual seup

    - by BWRic
    We currently use cPanel / WHM on a reseller account but are looking at getting a dedicated server. My first thought was to duplicate this set up on the dedicated box to allow us to quickly create new accounts. I'll be a managed server so they'll have set up the LAMP stack. I'm curious if I actually need cPanel and WHM. We don't use many of the features from cPanel / WHM, just creating accounts and databases, clients do not have FTP access. I'm no sys admin and come from a Windows / GUI background but have some knowledge in setting up development servers. WHM: Creating accounts I presume this sets up the Apache virtual host, FTP access and DNS settings. I've some knowledge of editing the Apache files to create virtual hosts. Am I correct in thinking as long as the DNS is pointing to the server IP and the virtual host is configured the server can serve the (php) pages? I'm not sure I need per site FTP access as only we will have access so I could have a server wide/htdocs only access to view all the site. The company who supply the dedicated hosts would also provide the own DNS management tool so I'm not need to cPanel one. MySQL: Creating users and databases We use cPanel to create the MySQL users and databases. As it's a dedicated box and I can have root access I think this could be replaced by SQLyog for db management and phpMyAdmin for user management. Do you I need cPanel or can I get by editing a few text files for creating the accounts, then use the MySQL tools for databases? Or am I missing something major with how the sites are configured?

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  • How can I fix the #c3284d# malvertising hack on my website?

    - by crm
    For the past couple of weeks at semi regular intervals, this website has had the #c3284d# malware code inserted into some of its .php files. Also the .htaccess file had its equivelant code inserted. I have, on many occasions removed the malicious code, replaced files, changed the ftp password on my ftp client (which is CoreFTP), changed the connection method to FTPS for more secure storage of the password (instead of plain text). I have also scanned my computer several times using AVG and Windows Defender which have found no malware on my computer which might have been storing my ftp passwords. I used Sucuri SiteCheck to check my website which says my website is clean of malware which is bizarre because I just attempted to click one of the links on the site a minute ago and it linked me to another one of these random stats.php sites, even though it appears I have gotten rid of the #c3284d# code again (which will no doubt be re-inserted somehow in an hour or so).. Has anyone found an actual viable solution for this malware hack? I have done just about all of the things suggested here and here and the problem still persists. Currently when I click on a link within the sites navigation menu within Google Chrome I get googles Malware warning page: Warning: Something's Not Right Here! oxsanasiberians.com contains malware. Your computer might catch a virus if you visit this site. Google has found that malicious software may be installed onto your computer if you proceed. If you've visited this site in the past or you trust this site, it's possible that it has just recently been compromised by a hacker. You should not proceed. Why not try again tomorrow or go somewhere else? We have already notified oxsanasiberians.com that we found malware on the site. For more about the problems found on oxsanasiberians.com, visit the Google Safe Browsing diagnostic page. I'm wondering if it is possible that the Google Chrome browser I am using has itself been hacked? Does anyone else get re-directed when clicking links on the the website?

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  • Closer look at the SOA 12c Feature: Oracle Managed File Transfer

    - by Tshepo Madigage-Oracle
    The rapid growth of cloud-based applications in the enterprise, combined with organizations' desire to integrate applications with mobile technologies, is dramatically increasing application integration complexity. To meet this challenge, Oracle introduced Oracle SOA Suite 12c, the latest version of the industry's most complete and unified application integration and SOA solution. With simplified cloud, mobile, on-premises, and Internet of Things (IoT) integration capabilities, all within a single platform, Oracle SOA Suite 12c helps organizations speed time to integration, improve productivity, and lower TCO. To extend its B2B solution capabilities with Oracle SOA Suite 12c, Oracle unveiled Oracle Managed File Transfer, an integrated solution that enables organizations to virtually eliminate file transfer complexities. This allows customers to load data securely into Oracle Cloud applications as well as third-party cloud or partner applications. Oracle Managed File Transfer (Oracle MFT) enables secure file exchange and management with internal departments and external partners. It protects against inadvertent access to unsecured files at every step in the end-to-end transfer of files. It is easy to use especially for non technical staff so you can leverage more resources to manage the transfer of files. The extensive reporting capabilities allow you to get quick status of a file transfer and resubmit it as required. You can protect data in your DMZ by using the SSH/FTP reverse proxy. Oracle Managed File Transfer can help integrate applications by transferring files between them in complex use case patterns. Standalone: Transferring files on its own using embedded FTP and sFTP servers and the file systems to which it has access. SOA Integration: a SOA application can be the source or target of a transfer. A SOA application can also be the common endpoint for the target of one transfer and the source of another. B2B Integration: B2B application can be the source or target of a transfer. A B2B application can also be the common endpoint for the target of one transfer and the source of another. Healthcare Integration:  Healthcare application can be the source or target of a transfer. A Healthcare application can also be the common endpoint for the target of one transfer and the source of another. Oracle Service Bus (OSB) integration: OMT can integrate with Oracle Service Bus web service interfaces. OSB interface can be the source or target of a transfer. An Oracle Service Bus interface can also be the common endpoint for the target of one transfer and the source of another. Hybrid Integration: can be one participant in a web of data transfers that includes multiple application types. Oracle Managed File Transfers has four user roles: file handlers, designers, monitors, and administrators. File Handlers: - Copy files to file transfer staging areas, which are called sources. - Retrieve files from file transfer destinations, which are called targets. Designers: - Create, read, update and delete file transfer sources. - Create, read, update and delete file transfer targets. - Create, read, update and delete transfers, which link sources and targets in complete file delivery flows. - Deploy and test transfers. Monitors: - Use the Dashboard and reports to ensure that transfer instances are successful. - Pause and resume lengthy transfers. - Troubleshoot errors and resubmit transfers. - View artifact deployment details and history. - View artifact dependence relationships. - Enable and disable sources, targets, and transfers. - Undeploy sources, targets, and transfers. - Start and stop embedded FTP and sFTP servers. Administrators: - All file handler tasks - All designer tasks - All monitor tasks - Add other users and determine their roles - Configure user directory permissions - Configure the Oracle Managed File Transfer server - Configure embedded FTP and sFTP servers, including security - Configure B2B and Healthcare domains - Back up and restore the Oracle Managed File Transfer configuration - Purge transferred files and instance data - Archive and restore instance data and payloads - Import and export metadata You will find all the related information about SOA 12.1.3. Oracle Manages File Transfer OMT in the documentation: Using Oracle Manages File Transfer Resources and links: Oracle Unveils Oracle SOA Suite 12c Oracle Managed Files Transfer Oracle Managed Files Transfer SOA 12c White Paper For further enquiries don't hesitate to contact us at [email protected] and join our Partner Webcast on Oracle SOA Suite 12c

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  • General website publishing questions involving domain forwarding issue

    - by Gorgeousyousuf
    Even though I have been having a certain level of knowledge and experience about web development I have never interested in obtaining a domain and publishing a website from my own server. Since today I have been struggling with getting my own domain and configuring it utilizing web sources. I started with learning the outline of web publishing process including web server installation, deploying a website for testing purpose,router port forwarding, getting a domain and forwarding domain to my router which will also forward http requests to my web server I am confused about some parts and so far could not get the web site accessed from outside of the network. All I try to do is just for learning purpose so I do not pay much attention to security issues for now. I have Server 2008 and IIS 7.5 installed. I use a laptop and have access to the modem over wireless and my modem is Zoom x6 5590. Well I will continue explaining what I have done so far and what I think will be after each action I did, I have successfully had access to my website on any local computer entering the internal ip address and port pair of the host machine in a browser. Next, I forwarded port 80 of my host machine creating a virtual server like 10.0.0.x(internal ip(static) of the host) - tcp - start port : 80 - end port : 80 in router options. Now I suppose every request that will come to the public Ip on port 80 will be forwarded to my host machine(10.0.0.x) over port 80. So If everyhing went as desired, the website listening on port 80 will accept the request and process the issue and finally respond bla bla bla... I suppose to access my website from outside of the network by entering http://MyPublicIp:80 in a browser but I couldn't accomplish this task by now despite using godady's domain forwarding tool,I see a small view of my website when I click the "preview" button that checks whether the address(http://publicip/Index.aspx) I entered where my domain will be forwarded is available or not. I am sure that configuring domain does not play a role in solving such a problem since using public ip and port matching does not help. So here is the first question, What is the fact that I face this problem? After that, I have couple of question regarding domain forwarding using godaddy tool. Can I forward my domain to a any port for example port 8080 other than default http port 80? Additionally, can I use a sub-domain to forward to a different port of the host? What I want to design is if the client enters www.mydomain.com, website1 will respond over a specified port and after when a client enters info.mydomain.com, another website which listens on different port will respond. I tried to add a sub-domain and forward it to a address like http://www.mydomain.com:8080/Index.aspx with no success. Can I really do that? Finally, what if I have a ftp site listening on the default port 21 and I create a domain like ftp.mydomain.com that will forward to that ftp site address. Is it possible to use sub-domains for ftp site access? I know I am more than confused but no matter whatever and however you reply to me, you will help me have a more clear view on this subject. Thank you very much from now.

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  • C#: Cannot handle redirect from HTTP/HTTPS protocols to other dissimilar ones

    - by Peanut
    Basically, I'm trying to grab an EXE from CNet's Download.com So i created web parser and so far all is going well. Here is a sample link pulled directly from their site: http://dw.com.com/redir?edId=3&siteId=4&oId=3001-20_4-10308491&ontId=20_4&spi=e6323e8d83a8b4374d43d519f1bd6757&lop=txt&tag=idl2&pid=10566981&mfgId=6250549&merId=6250549&pguid=PlvcGQoPjAEAAH5rQL0AAABv&destUrl=ftp%3A%2F%2F202.190.201.108%2Fpub%2Fryl2%2Fclient%2Finstaller-ryl2_v1673.exe Here is the problem: When you attempt to download, it begins with HTTP, then redirects to an FTP site. I have tried .NET's WebClient and HttpWebRequest Objects, and it looks like Neither can support Redirects. This Code Fails at GetResponse(); HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://dw.com.com/redir?edId=3&siteId=4&oId=3001-20_4-10308491&ontId=20_4&spi=e6323e8d83a8b4374d43d519f1bd6757&lop=txt&tag=idl2&pid=10566981&mfgId=6250549&merId=6250549&pguid=PlvcGQoPjAEAAH5rQL0AAABv&destUrl=ftp%3A%2F%2F202.190.201.108%2Fpub%2Fryl2%2Fclient%2Finstaller-ryl2_v1673.exe"); WebResponse response = req.GetResponse(); Now, I also tried this: HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://dw.com.com/redir?edId=3&siteId=4&oId=3001-20_4-10308491&ontId=20_4&spi=e6323e8d83a8b4374d43d519f1bd6757&lop=txt&tag=idl2&pid=10566981&mfgId=6250549&merId=6250549&pguid=PlvcGQoPjAEAAH5rQL0AAABv&destUrl=ftp%3A%2F%2F202.190.201.108%2Fpub%2Fryl2%2Fclient%2Finstaller-ryl2_v1673.exe"); req.AllowAutoRedirect = false; WebResponse response = req.GetResponse(); string s = new StreamReader(response.GetResponseStream()).ReadToEnd(); And it does not throw the error anymore, however variable s turns out to be an empty string. I'm at a loss! Can anyone help out?

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  • Incremental deploy from a shell script

    - by WishCow
    I have a project, where I'm forced to use ftp as a means of deploying the files to the live server. I'm developing on linux, so I hacked together a bash script that makes a backup of the ftp server's contents, deletes all the files on the ftp, and uploads all the fresh files from the mercurial repository. (and taking care of user uploaded files and folders, and making post-deploy changes, etc) It's working well, but the project is starting to get big enough to make the deployment process too long. I'd like to modify the script to look up which files have changed, and only deploy the modified files. (the backup is fine atm as it is) I'm using mercurial as a VCS, so my idea is to somehow request the changed files between two revisions from it, iterate over the changed files, and upload each modified file, and delete each removed file. I can use hg log -vr rev1:rev2, and from the output, I can carve out the changed files with grep/sed/etc. Two problems: I have heard the horror stories that parsing the output of ls leads to insanity, so my guess is that the same applies to here, if I try to parse the output of hg log, the variables will undergo word-splitting, and all kinds of transformations. hg log doesn't tell me a file is modified/added/deleted. Differentiating between modified and deleted files would be the least. So, what would be the correct way to do this? I'm using yafc as an ftp client, in case it's needed, but willing to switch.

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  • shell script stopped working --- need to rewrite?

    - by OopsForgotMyOtherUserName
    The script below worked on my Mac OS X. I'm now using Ubuntu OS, and the script is no longer working. I'm wondering if there's something that I need to change here? I did change the first line from #!/bin/bash to #!/bin/sh, but it's still throwing up an error.... Essentially, I get an error when I try to run it: Syntax error: end of file unexpected (expecting ")") #!/bin/sh REMOTE='ftp.example.com' USER='USERNAME' PASSWORD='PASSWORD' CMDFILE='/jtmp/rc.ftp' FTPLOG='/jtmp/ftplog' PATTERN='SampFile*' date > $FTPLOG rm $CMDFILE 2>/dev/null LISTING=$(ftp -in $REMOTE <<EOF user $USER $PASSWORD cd download ls $PATTERN quit EOF ) echo "open $REMOTE" >> $CMDFILE echo "user $USER $PASSWORD" >> $CMDFILE echo "verbose" >> $CMDFILE echo "bin" >> $CMDFILE echo "cd download" >> $CMDFILE for FILE in $LISTING do echo "get $FILE" >> $CMDFILE done echo "quit" >> $CMDFILE ftp -in < $CMDFILE >> $FTPLOG 2>&1 rm $CMDFILE

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  • DTracing TCP congestion control

    - by user12820842
    In a previous post, I showed how we can use DTrace to probe TCP receive and send window events. TCP receive and send windows are in effect both about flow-controlling how much data can be received - the receive window reflects how much data the local TCP is prepared to receive, while the send window simply reflects the size of the receive window of the peer TCP. Both then represent flow control as imposed by the receiver. However, consider that without the sender imposing flow control, and a slow link to a peer, TCP will simply fill up it's window with sent segments. Dealing with multiple TCP implementations filling their peer TCP's receive windows in this manner, busy intermediate routers may drop some of these segments, leading to timeout and retransmission, which may again lead to drops. This is termed congestion, and TCP has multiple congestion control strategies. We can see that in this example, we need to have some way of adjusting how much data we send depending on how quickly we receive acknowledgement - if we get ACKs quickly, we can safely send more segments, but if acknowledgements come slowly, we should proceed with more caution. More generally, we need to implement flow control on the send side also. Slow Start and Congestion Avoidance From RFC2581, let's examine the relevant variables: "The congestion window (cwnd) is a sender-side limit on the amount of data the sender can transmit into the network before receiving an acknowledgment (ACK). Another state variable, the slow start threshold (ssthresh), is used to determine whether the slow start or congestion avoidance algorithm is used to control data transmission" Slow start is used to probe the network's ability to handle transmission bursts both when a connection is first created and when retransmission timers fire. The latter case is important, as the fact that we have effectively lost TCP data acts as a motivator for re-probing how much data the network can handle from the sending TCP. The congestion window (cwnd) is initialized to a relatively small value, generally a low multiple of the sending maximum segment size. When slow start kicks in, we will only send that number of bytes before waiting for acknowledgement. When acknowledgements are received, the congestion window is increased in size until cwnd reaches the slow start threshold ssthresh value. For most congestion control algorithms the window increases exponentially under slow start, assuming we receive acknowledgements. We send 1 segment, receive an ACK, increase the cwnd by 1 MSS to 2*MSS, send 2 segments, receive 2 ACKs, increase the cwnd by 2*MSS to 4*MSS, send 4 segments etc. When the congestion window exceeds the slow start threshold, congestion avoidance is used instead of slow start. During congestion avoidance, the congestion window is generally updated by one MSS for each round-trip-time as opposed to each ACK, and so cwnd growth is linear instead of exponential (we may receive multiple ACKs within a single RTT). This continues until congestion is detected. If a retransmit timer fires, congestion is assumed and the ssthresh value is reset. It is reset to a fraction of the number of bytes outstanding (unacknowledged) in the network. At the same time the congestion window is reset to a single max segment size. Thus, we initiate slow start until we start receiving acknowledgements again, at which point we can eventually flip over to congestion avoidance when cwnd ssthresh. Congestion control algorithms differ most in how they handle the other indication of congestion - duplicate ACKs. A duplicate ACK is a strong indication that data has been lost, since they often come from a receiver explicitly asking for a retransmission. In some cases, a duplicate ACK may be generated at the receiver as a result of packets arriving out-of-order, so it is sensible to wait for multiple duplicate ACKs before assuming packet loss rather than out-of-order delivery. This is termed fast retransmit (i.e. retransmit without waiting for the retransmission timer to expire). Note that on Oracle Solaris 11, the congestion control method used can be customized. See here for more details. In general, 3 or more duplicate ACKs indicate packet loss and should trigger fast retransmit . It's best not to revert to slow start in this case, as the fact that the receiver knew it was missing data suggests it has received data with a higher sequence number, so we know traffic is still flowing. Falling back to slow start would be excessive therefore, so fast recovery is used instead. Observing slow start and congestion avoidance The following script counts TCP segments sent when under slow start (cwnd ssthresh). #!/usr/sbin/dtrace -s #pragma D option quiet tcp:::connect-request / start[args[1]-cs_cid] == 0/ { start[args[1]-cs_cid] = 1; } tcp:::send / start[args[1]-cs_cid] == 1 && args[3]-tcps_cwnd tcps_cwnd_ssthresh / { @c["Slow start", args[2]-ip_daddr, args[4]-tcp_dport] = count(); } tcp:::send / start[args[1]-cs_cid] == 1 && args[3]-tcps_cwnd args[3]-tcps_cwnd_ssthresh / { @c["Congestion avoidance", args[2]-ip_daddr, args[4]-tcp_dport] = count(); } As we can see the script only works on connections initiated since it is started (using the start[] associative array with the connection ID as index to set whether it's a new connection (start[cid] = 1). From there we simply differentiate send events where cwnd ssthresh (congestion avoidance). Here's the output taken when I accessed a YouTube video (where rport is 80) and from an FTP session where I put a large file onto a remote system. # dtrace -s tcp_slow_start.d ^C ALGORITHM RADDR RPORT #SEG Slow start 10.153.125.222 20 6 Slow start 138.3.237.7 80 14 Slow start 10.153.125.222 21 18 Congestion avoidance 10.153.125.222 20 1164 We see that in the case of the YouTube video, slow start was exclusively used. Most of the segments we sent in that case were likely ACKs. Compare this case - where 14 segments were sent using slow start - to the FTP case, where only 6 segments were sent before we switched to congestion avoidance for 1164 segments. In the case of the FTP session, the FTP data on port 20 was predominantly sent with congestion avoidance in operation, while the FTP session relied exclusively on slow start. For the default congestion control algorithm - "newreno" - on Solaris 11, slow start will increase the cwnd by 1 MSS for every acknowledgement received, and by 1 MSS for each RTT in congestion avoidance mode. Different pluggable congestion control algorithms operate slightly differently. For example "highspeed" will update the slow start cwnd by the number of bytes ACKed rather than the MSS. And to finish, here's a neat oneliner to visually display the distribution of congestion window values for all TCP connections to a given remote port using a quantization. In this example, only port 80 is in use and we see the majority of cwnd values for that port are in the 4096-8191 range. # dtrace -n 'tcp:::send { @q[args[4]-tcp_dport] = quantize(args[3]-tcps_cwnd); }' dtrace: description 'tcp:::send ' matched 10 probes ^C 80 value ------------- Distribution ------------- count -1 | 0 0 |@@@@@@ 5 1 | 0 2 | 0 4 | 0 8 | 0 16 | 0 32 | 0 64 | 0 128 | 0 256 | 0 512 | 0 1024 | 0 2048 |@@@@@@@@@ 8 4096 |@@@@@@@@@@@@@@@@@@@@@@@@@@ 23 8192 | 0

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  • Updating Debian kernel

    - by Devator
    I'm trying to update my Debian machine to 2.6.32-46 (which is the new stable). However, after doing apt-get update my apt-cache search linux-image shows me: linux-headers-2.6.32-5-486 - Header files for Linux 2.6.32-5-486 linux-headers-2.6.32-5-686-bigmem - Header files for Linux 2.6.32-5-686-bigmem linux-headers-2.6.32-5-686 - Header files for Linux 2.6.32-5-686 linux-headers-2.6.32-5-amd64 - Header files for Linux 2.6.32-5-amd64 linux-headers-2.6.32-5-openvz-686 - Header files for Linux 2.6.32-5-openvz-686 linux-headers-2.6.32-5-vserver-686-bigmem - Header files for Linux 2.6.32-5-vser ver-686-bigmem linux-headers-2.6.32-5-vserver-686 - Header files for Linux 2.6.32-5-vserver-686 linux-headers-2.6.32-5-xen-686 - Header files for Linux 2.6.32-5-xen-686 linux-image-2.6.32-5-486 - Linux 2.6.32 for old PCs linux-image-2.6.32-5-686-bigmem-dbg - Debugging infos for Linux 2.6.32-5-686-big mem linux-image-2.6.32-5-686-bigmem - Linux 2.6.32 for PCs with 4GB+ RAM linux-image-2.6.32-5-686 - Linux 2.6.32 for modern PCs linux-image-2.6.32-5-amd64 - Linux 2.6.32 for 64-bit PCs linux-image-2.6.32-5-openvz-686-dbg - Debugging infos for Linux 2.6.32-5-openvz- 686 linux-image-2.6.32-5-openvz-686 - Linux 2.6.32 for modern PCs, OpenVZ support linux-image-2.6.32-5-vserver-686-bigmem-dbg - Debugging infos for Linux 2.6.32-5 -vserver-686-bigmem linux-image-2.6.32-5-vserver-686-bigmem - Linux 2.6.32 for PCs with 4GB+ RAM, Li nux-VServer support linux-image-2.6.32-5-vserver-686 - Linux 2.6.32 for modern PCs, Linux-VServer su pport linux-image-2.6.32-5-xen-686-dbg - Debugging infos for Linux 2.6.32-5-xen-686 linux-image-2.6.32-5-xen-686 - Linux 2.6.32 for modern PCs, Xen dom0 support linux-image-2.6-486 - Linux 2.6 for old PCs (meta-package) linux-image-2.6-686-bigmem - Linux 2.6 for PCs with 4GB+ RAM (meta-package) linux-image-2.6-686 - Linux 2.6 for modern PCs (meta-package) linux-image-2.6-amd64 - Linux 2.6 for 64-bit PCs (meta-package) linux-image-2.6-openvz-686 - Linux 2.6 for modern PCs (meta-package), OpenVZ sup port linux-image-2.6-vserver-686-bigmem - Linux 2.6 for PCs with 4GB+ RAM (meta-packa ge), Linux-VServer support linux-image-2.6-vserver-686 - Linux 2.6 for modern PCs (meta-package), Linux-VSe rver support linux-image-2.6-xen-686 - Linux 2.6 for modern PCs (meta-package), Xen dom0 supp ort linux-image-486 - Linux for old PCs (meta-package) linux-image-686-bigmem - Linux for PCs with 4GB+ RAM (meta-package) linux-image-686 - Linux for modern PCs (meta-package) linux-image-amd64 - Linux for 64-bit PCs (meta-package) linux-image-openvz-686 - Linux for modern PCs (meta-package), OpenVZ support linux-image-vserver-686-bigmem - Linux for PCs with 4GB+ RAM (meta-package), Lin ux-VServer support linux-image-vserver-686 - Linux for modern PCs (meta-package), Linux-VServer sup port linux-image-xen-686 - Linux for modern PCs (meta-package), Xen dom0 support So, 2.6.32-46 doesn't seem to be found. How can I update to this kernel? My sources.list: ###### Debian Main Repos deb http://ftp.nl.debian.org/debian/ squeeze main contrib deb-src http://ftp.nl.debian.org/debian/ squeeze main contrib ###### Debian Update Repos deb http://security.debian.org/ squeeze/updates main contrib deb http://ftp.nl.debian.org/debian/ squeeze-proposed-updates main contrib deb-src http://security.debian.org/ squeeze/updates main contrib deb-src http://ftp.nl.debian.org/debian/ squeeze-proposed-updates main contrib

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  • Proftp error message Fatal: unknown configuration directive 'DisplayFirstChdir' on line 22 of '/etc/proftpd/proftpd.conf'

    - by LedZeppelin
    Sorry for the newb factor but I'm trying to set up a server using this guide: http://www.intac.net/build-your-own-server/ I'm at the end of step 5 and when I try to restart proftp I get the following error message me@me-desktop:~$ sudo service proftpd restart * Stopping ftp server proftpd [ OK ] * Starting ftp server proftpd Fatal: unknown configuration directive 'DisplayFirstChdir' on line 22 of '/etc/proftpd/proftpd.conf' [fail] Any clues on how to change line 22?

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  • OpenVPN Clients using server's connection (with no default gateway)

    - by Branden Martin
    I wanted an OpenVPN server so that I could create a private VPN network for staff to connect to the server. However, not as planned, when clients connect to the VPN, it's using the VPN's internet connection (ex: when going to whatsmyip.com, it's that of the server and not the clients home connection). server.conf local <serverip> port 1194 proto udp dev tun ca ca.crt cert x.crt key x.key dh dh1024.pem server 10.8.0.0 255.255.255.0 ifconfig-pool-persist ipp.txt client-to-client keepalive 10 120 comp-lzo persist-key persist-tun status openvpn-status.log verb 9 client.conf client dev tun proto udp remote <srever> 1194 resolv-retry infinite nobind persist-key persist-tun ca ca.crt cert x.crt key x.key ns-cert-type server comp-lzo verb 3 Server's route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.8.0.2 * 255.255.255.255 UH 0 0 0 tun0 10.8.0.0 10.8.0.2 255.255.255.0 UG 0 0 0 tun0 69.64.48.0 * 255.255.252.0 U 0 0 0 eth0 default static-ip-69-64 0.0.0.0 UG 0 0 0 eth0 default static-ip-69-64 0.0.0.0 UG 0 0 0 eth0 default static-ip-69-64 0.0.0.0 UG 0 0 0 eth0 Server's IP Tables Chain INPUT (policy ACCEPT) target prot opt source destination fail2ban-proftpd tcp -- anywhere anywhere multiport dports ftp,ftp-data,ftps,ftps-data fail2ban-ssh tcp -- anywhere anywhere multiport dports ssh ACCEPT udp -- anywhere anywhere udp dpt:domain ACCEPT tcp -- anywhere anywhere tcp dpt:20000 ACCEPT tcp -- anywhere anywhere tcp dpt:webmin ACCEPT tcp -- anywhere anywhere tcp dpt:https ACCEPT tcp -- anywhere anywhere tcp dpt:www ACCEPT tcp -- anywhere anywhere tcp dpt:imaps ACCEPT tcp -- anywhere anywhere tcp dpt:imap2 ACCEPT tcp -- anywhere anywhere tcp dpt:pop3s ACCEPT tcp -- anywhere anywhere tcp dpt:pop3 ACCEPT tcp -- anywhere anywhere tcp dpt:ftp-data ACCEPT tcp -- anywhere anywhere tcp dpt:ftp ACCEPT tcp -- anywhere anywhere tcp dpt:domain ACCEPT tcp -- anywhere anywhere tcp dpt:smtp ACCEPT tcp -- anywhere anywhere tcp dpt:ssh ACCEPT all -- anywhere anywhere Chain FORWARD (policy ACCEPT) target prot opt source destination ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT all -- 10.8.0.0/24 anywhere REJECT all -- anywhere anywhere reject-with icmp-port-unreachable Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain fail2ban-proftpd (1 references) target prot opt source destination RETURN all -- anywhere anywhere Chain fail2ban-ssh (1 references) target prot opt source destination RETURN all -- anywhere anywhere My goal is that clients can only talk to the server and other clients that are connected. Hope I made sense. Thanks for the help!

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  • Linux users traffic measurement

    - by Claudiu
    I want to measure traffic(upload) made by each user on a linux system. Each users runs a rTorrent instance on a specified port. Also users could make traffic through the ftp server (vsftpd). Is there a tool that can monitor traffic for a specified port and for ftp users ?

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  • Difference between adding MIME types in IIS via Websites vs Local Computer?

    - by Alex Key
    What is the difference between adding MIME types in these 2 different situations? When in IIS 6 manager... Right click on the computer name (local computer) properties mime types Right click on the "Web sites" folder properties http headers mime types I'm guessing that perhaps option 1 adds MIME types for FTP also? However if that were true i'd expect to be able to add MIME types specifically in the properties of FTP (and not just websites). thanks for your help.

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