Server Circle - Member profile for JimmyC


shopt -s histappend
PROMPT_COMMAND="history -a; $PROMPT_COMMAND"
export HISTSIZE=1000
export HISTFILESIZE=1000
export HISTTIMEFORMAT="%h/%d - %H:%M:%S "
export HISTIGNORE="[ ]*"

I think /etc/bash.bashrc is how to set it for all users on some Linux distros. In the home directory . .bash_profile will reload the profile but some distros prefer if you log in and out again. I always add export HISTIGNORE="[ ]*" which I think is quite clever. One low-risk application I use insists on having a password entered into the command line. To ignore it from being saved in Bash's History simply start the command line with a space and it won't be written to the .bash_history file. Use it to simply ignore a command that you don't want to save too.

I have Centos system with customized application running on it. I want to make bootable usb drive from above. How can I do this ?

Asked in: CentOS-Linux-Servers (1 answers)
JimmyC's response: Have a look at: http://techie-buzz.com/foss/create-bootable-usb-drive-for-centosredhat.html If that isn't what you need try unetbootin. It's a multi-OS USB stick creator and very good (although a bit buggy): http://unetbootin.sourceforge.net

Why is this showing up in the logs on a new install of Postfix on Ubuntu Linux Server ? (Host or domain name not found. Name service error for name=domain.com type=MX: Host not found, try again) Thank you.

Asked in: Ubuntu-Linux-Servers (1 answers)
JimmyC's response: Check /etc/resolv.conf it looks like DNS lookups are failing.

I need strip the last few characters off a string in PHP - from the eleventh character of a word I don't want it to be any longer. Is this possible ? Thank you.

Asked in: OtherProgramming (2 answers)
JimmyC's response: This should help: http://www.php.net/manual/en/function.substr-replace.php


$var = 'ABCDEFGH:/MNRPQR/';

/* These two examples replace all of $var with 'bob'. */
echo substr_replace($var, 'bob', 0) . "
\n";
echo substr_replace($var, 'bob', 0, strlen($var)) . "
\n";

/* Insert 'bob' right at the beginning of $var. */
echo substr_replace($var, 'bob', 0, 0) . "
\n";

/* These next two replace 'MNRPQR' in $var with 'bob'. */
echo substr_replace($var, 'bob', 10, -1) . "
\n";
echo substr_replace($var, 'bob', -7, -1) . "
\n";

/* Delete 'MNRPQR' from $var. */
echo substr_replace($var, '', 10, -1) . "
\n";

I'm getting slow ftp uploads to my FileZilla server from the internet side of the router using FireFTP - typically speeds of only about 10Kb (inside the LAN everything's speedy enough). The speeds initially start out much higher - 100Kb+ - but rapidly drop to 10Kb or less. This is despite the broadband speed of the connections at each end being around the 10-meg mark. I tried FileZilla Client - same thing. I have no speed limits, global or individual user, set. Maximum number of threads is set at 10 and the number of connections is set at 0 (unlimited) for future use, but these slow speeds are happening during the testing phase of setting up the server with only one user defined and connected. Any ideas what could be the cause of this? Are there any good diagnostic tools in people's toolkits that might help me find the cause if there is one?

Asked in: Linux-Servers (11 answers)
JimmyC's response: Yes, you're right. All you want to check is that your ISP is giving you what you expect (ie more than 10kbps !). You're checking the network is working correctly before looking at the application. So if it's an ADSL line and you connect at 8Mbps, the chances are you'll get 4Mbps in the UK as a yardstick. The results from these tools are just in Mbit or Kbit. Remember kbps and KB/s are different ! Try and stick to kbps and megs for ease.

Asked in: Linux-Servers (11 answers)
JimmyC's response: A couple of thoughts spring to mind: Don't be too certain about the connection starting correctly and then throttling back. The difference between what you can fit down the pipe and the maximum speed of the pipe is always pretty different, in simple terms. Check your speed and duplex on the NICs. You might get fast UDP and erratic TCP if you have one NIC accidentally at HD not FD. You might not notice this in a LAN because latency is far less usually. The best tools are iperf and netcat (use nc -l ...) for throughput testing. I know it sounds rudimentary but spend 10 minutes checking your *actual* connection speeds with one or both of these tools. You'd be surprised how poor some DSL performance is .... really :) You can then get deeper into config parameters if you're 100% certain that the network is as you'd expect.

How can I connect my two computers running from Ubuntu 11.04 by using a cross over cable, so that I can transfer data between these two computers ?

Asked in: Ubuntu-Linux-Servers (1 answers)
JimmyC's response: All you would do it allocate a private IP address to each computer's network card, in /etc/network/interfaces. See here: http://tinyurl.com/2oxnnw Just have one as 10.10.10.10 and the other as 10.10.10.11 with 255.255.255.0 as the subnet mask. To be sure they can communicate run a few ping tests. Once both computers can ping each other you can use something like sFTP or Samba to move files back and forth. This might help, otherwise look up installing "openssh server" and using sFTP. http://www.howtogeek.com/howto/ubuntu/install-samba-server-on-ubuntu/

Can you integrate virus scanners into FTP servers these days ? I haven't used ClamAV for ages. Thanks.

Asked in: Debian-Linux-Servers (1 answers)
JimmyC's response: After more hunting I found this on Debian: http://www.howtoforge.com/how-to-integrate-clamav-into-pureftpd-for-virus-scanning-on-debian-lenny Excellent.

I am new to Linux world and I need help in understanding yum server.

Asked in: RedHat-Linux-Servers (3 answers)
JimmyC's response: This should give you a good starting point: http://tinyurl.com/4x2rdua

I need a script to check temperature in a server and then email me if it gets past 50 degrees celcius. Using a hard drive's temperature would be fine I think. I've tried writing my own script using hddtemp but I'm no good at Bash. A �5 Amazon voucher is up for grabs for helping me out. Thanks.

Asked in: ShellScripts (5 answers)
JimmyC's response: Something like this should do it, if hddtemp is installed: #!/bin/bash value=0; hddtemp -q /dev/sda > /tmp/.check_temp; value=`awk '{ print $3 }' /tmp/.check_temp | sed -e ' s/�C//'`; if [ $value -gt 49 ] then echo "Temperature is $value degrees C " > /tmp/mail_file; mailx -s "ALARM" mail@domain.com < /tmp/mail.file else exit 0 fi

I have used checkrestart from debian-goodies to see if some old library files are still in use after a package update on Debian and Ubuntu. I have a list of kernel packages, libc packages and d-bus package updates that definitely need a server reboot. I use Uptrack from www.ksplice.com to keep the kernel reboots to a minimum (it's great so far) but I need to know when to reboot after other package updates (and only when necessary). The best answer will get 50 points and an £10 Amazon voucher. Tell me which Amazon site you use if you get selected. Cheers.

Asked in: Debian-Linux-Servers (15 answers)
JimmyC's response: I understand but on a very important production server you can't introduce instability, especially when tools like Uptrack from ksplice.com mean that a server may be up for several months at a time. From what I've seen there's no immediate issue with something like libc upgrading but at some undetermined point later on a critical service crashing isn't welcome, especially if you then spend ages trying to diagnose it. Also it's not possible to -HUP quite a few Debian-based services without knocking over key services, the d-bus example being one.

Asked in: Debian-Linux-Servers (15 answers)
JimmyC's response: But libc is used by almost every package on a Debian-based system and running some services on older libraries and some on new at the same time is a recipe for instability. Surely ? My experience of Gentoo tells me that at least libc can universally break an entire system after an upgrade without a reboot :) I learned the "Gentoo" way :)

Asked in: Debian-Linux-Servers (15 answers)
JimmyC's response: More here: http://www.linux-archive.org/ubuntu-user/437233-upgraded-packages-require-restart.html

Asked in: Debian-Linux-Servers (15 answers)
JimmyC's response: I think this is where my info on d-bus partially came from: https://wiki.ubuntu.com/DbusRestart I almost tried restarting dbus on a server then to see, and I'm VERY glad I didn't. I tried it on a desktop and the whole machine failed and needed powered off and on again !

Asked in: Debian-Linux-Servers (15 answers)
JimmyC's response: That's interesting. Do you have any links saying that libc and dbus don't need a reboot ? It's not what I've found, searching for info on this. How do you reload d-bus on a Debian machine ? I'm not sure.

Asked in: Debian-Linux-Servers (15 answers)
JimmyC's response: Thank you for the script. That will be useful. On Debian and Ubuntu there is actually a mechanism for saying which packages need a reboot after being updated but it seems that the maintainers of some packages don't always follow protocol and add it correctly and therefore it's unreliable. Basically if this exists then when you login a note is triggered /var/run/reboot-required.pkgs. Ksplice sidesteps this with this script in /usr/share/update-notifier/notify-reboot-required.

#!/bin/sh
# Ksplice: don't notify about reboots required by kernel upgrades

if echo "$DPKG_MAINTSCRIPT_PACKAGE" | grep -q "^linux-image-2[.]6[.]"; then
    # Add another line to the list of reboots we've saved.
    echo "$DPKG_MAINTSCRIPT_PACKAGE" $(date) >> /var/cache/uptrack/reboots_saved
elif echo "$DPKG_MAINTSCRIPT_PACKAGE" | grep -q "^libssl0.9.8"; then
    # Work around LP #244250, a bug in libssl configure script that
    # sends a reboot notification unnecessarily.
    true
else
    if [ -x /usr/share/update-notifier/notify-reboot-required.ksplice-orig ]; then
        /usr/share/update-notifier/notify-reboot-required.ksplice-orig "$@"
    fi
fi

I really just need a list I can trust which means fewer reboots for my production servers.

Asked in: Debian-Linux-Servers (15 answers)
JimmyC's response: Thanks, I'll clarify my question a bit further. My understanding is: I never want to run an unstable server by not rebooting when it's necessary (by running old and new libraries simultaneously that make it unstable or because the system is insecure because new patches haven't been properly applied) and I also only want to reboot when it's absolutely necessary because they are production servers. An example might be when lsof (through debian-goodies) can't find an /etc/init.d start/stop script to restart services that still have old libraries attached to them. I know that d-bus and libc need a reboot under those circumstances or the system will be unstable but not all daemons/services need a reboot and are important to maintaining stability so I'd like a comprehensive way of being able to tell or a list of absolutely critical updates that need a reboot.

How To Install Network Monitoring "Nagios" On Mandriva Please Help Me, Urgent!

Asked in: Linux-Servers (2 answers)
JimmyC's response: Does this help you at all ? It's translated into English through Google so proceed with caution :) http://tinyurl.com/6jd5r6q

Is it possible to use it on Ubuntu Server for backups ? It's seems like a good idea.

Asked in: Ubuntu-Linux-Servers (2 answers)
JimmyC's response: It's pretty easy to write a simple script around that tool.

Is there any way of knowing if this security update needs me to restart Apache on my web servers ? It's this update: http://www.debian.org/security/2011/dsa-2237 Thanks, I really hate stopping and starting Apache !

Asked in: Debian-Linux-Servers (3 answers)
JimmyC's response: I've just seen the last bit of that text on the advisory. Duh. I suppose a full "restart" and not just "reload" is needed ?

I don't want all the fake logins and need to change from port 22 but how do I do that ?

Asked in: Linux-Servers (2 answers)
JimmyC's response: Yes, it's worth changing the default port these days for sure.

Using PHP, is it possible to combine 2 pdfs such that one of them is used as a template for the other: I have 1 PDF which is laid out like a standard letterhead, with graphics in the header, and text in the footer. I have another PDF with the contents of a letter in it (margins set correctly for the layout). I want to use the letterhead template as an overlay on the content PDF, so that the resulting PDF is the actual letter with the letterhead template applied.

Asked in: OtherProgramming (1 answers)
JimmyC's response: I haven't used it but this looks similar: http://www.kennynet.co.uk/2008/11/26/php-and-pdf-templates/ Although templating makes sense, it might be easier to follow a header and footer approach in the long run.

Should I install DKIM ? I see Google and Yahoo use them but do anyone else ? The patching for Domain Keys in Postfix looks quite hard.

Asked in: Email-Servers (3 answers)
JimmyC's response: Great, thanks alot.

I have two identical drives in my new server and I'm going to put Ubuntu on it. What's the most reliable RAID config for automatically running off the other drive if a drive fails ? I've never used RAID before. Cheers for any help.

Asked in: Ubuntu-Linux-Servers (6 answers)
JimmyC's response: Thanks. Would this mean that if one drive failed I wouldn't need access to the Server (unless I was to replace the failed drive) but it would keep running automatically ?

Will any one please let me know what a DNS trigger is ?