I was trying to follow the instructions found here to set up a catch-all account, but still I get the following message for mails sent to non-existent users:
The error that the other server returned was: 550 550 5.1.1 [email protected]... User unknown (state 14).
Everything else works, though... /etc/mail/local-host-names and /etc/mail/virtusertable were set up as instructed. Any advice? Thanks!
I'm looking for help with what I'm sure is an age old question. I've found myself in a situation of yearning to understand network throughput more clearly, but I can't seem to find information that makes it "click"
We have a few servers distributed geographically, running various versions of Windows. Assuming we always use one host (a desktop) as the source, when copying data from that host to other servers across the country, we see a high variance in speed. In some cases, we can copy data at 12MB/s consistently, in others, we're seeing 0.8 MB/s. It should be noted, after testing 8 destinations, we always seem to be at either 0.6-0.8MB/s or 11-12 MB/s. In the building we're primarily concerned with, we have an OC-3 connection to our ISP.
I know there are a lot of variables at play, but I guess I was hoping the experts here could help answer a few basic questions to help bolster my understanding.
1.) For older machines, running Windows XP, server 2003, etc, with a 100Mbps Ethernet card and 72 ms typical latency, does 0.8 MB/s sound at all reasonable? Or do you think that slow enough to indicate a problem?
2.) The classic "mathematical fastest speed" of "throughput = TCP window / latency," is, in our case, calculated to 0.8 MB/s (64Kb / 72 ms). My understanding is that is an upper bounds; that you would never expect to reach (due to overhead) let alone surpass that speed. In some cases though, we're seeing speeds of 12.3 MB/s. There are Steelhead accelerators scattered around the network, could those account for such a higher transfer rate?
3.) It's been suggested that the use SMB vs. SMB2 could explain the differences in speed. Indeed, as expected, packet captures show both being used depending on the OS versions in play, as we would expect. I understand what determines SMB2 being used or not, but I'm curious to know what kind of performance gain you can expect with SMB2.
My problem simply seems to be a lack of experience, and more importantly, perspective, in terms of what are and are not reasonable network speeds. Could anyone help impart come context/perspective?
Which Linux server distribution the best to run lamp server for production environment?
1. sharing hosting
2. virtual hosting
3. dedicated hosting
(Ubuntu server, redhat,....)
Thanks,
Yosef
Can anyone recommend a linux command line tool to monitor the number of bytes transferred between the local server and a specified IP address/port.
The equivalent tcpdump command would be:
tcpdump -s 0 -i any -w mycapture.trc port 80 host google.com
which outputs :
46 packets captured
131 packets received by filter
0 packets dropped by kernel
I'd like something similar that outputs:
54 bytes out, 176 bytes in
I'd like it to work on RHEL and be free/open-source. It would be good if there was an existing tool which I was just missing too!
I'm experimenting with large changes to Linux system runtime parameters exposed through the sysfs virtual file system.
What is the most efficient way to maintain these parameters so that they persist across reboots on a RHEL/CentOS-style system? Is it simply dumping commands into /etc/rc.local? Is there an init script that's well-suited for this? I'm also thinking about standardization from a configuration management perspective. Is there a clean sysfs equivalent to sysctl?
My proxy server runs on ip A and this is how people access my web service. The nginx configuration will redirect to a virtual machine on ip B.
For the proxy server on IP A, I have this in my sites-available
server {
listen 443;
ssl on;
ssl_certificate nginx.pem;
ssl_certificate_key nginx.key;
client_max_body_size 200M;
server_name localhost 127.0.0.1;
server_name_in_redirect off;
location / {
proxy_pass http://10.10.0.59:80;
proxy_redirect http://10.10.0.59:80/ /;
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
server {
listen 80;
rewrite ^(.*) https://$http_host$1 permanent;
server_name localhost 127.0.0.1;
server_name_in_redirect off;
location / {
proxy_pass http://10.10.0.59:80;
proxy_redirect http://10.10.0.59:80/ /;
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
The proxy_redirect was taken from how do I get nginx to forward HTTP POST requests via rewrite?
Everything that hits the public IP will hit 443 because of the rewrite. Internally, we are forwarding to 80 on the virtual machine.
But when I run a python script such as the one below to test our configuration
import requests
data = {'username': '....', 'password': '.....'}
url = 'http://IP_A/api/service/signup'
res = requests.post(url, data=data, verify=False)
print res
print res.json
print res.status_code
print res.headers
I am getting a 405 Method Not Allowed. In nginx we found that when it hit the internal server, the internal nginx was getting a GET request, even though in the original header we did a POST (this was shown in the Python script).
So it seems like rewrite has problem. Any idea how to fix this? When I commented out the rewrite, it hits 80 for sure, and it went through. Since rewrite was able to talk to our internal server, so rewrite itself has no issue. It's just the rewrite dropped POST to GET.
Thank you!
(This will also be asked on Nginx forum because this is a critical blocker...)
I have a server (serv05) at work with a public ip, hosting two KVM guests - vtest1 & vtest2 - in two different private network - 192.168.122.0 & 192.168.100.0 - respectively, this way:
[root@serv05 ~]# ip -o addr show | grep -w inet
1: lo inet 127.0.0.1/8 scope host lo
2: eth0 inet xxx.xxx.xx.197/24 brd xxx.xxx.xx.255 scope global eth0
4: virbr1 inet 192.168.100.1/24 brd 192.168.100.255 scope global virbr1
6: virbr0 inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
#
[root@serv05 ~]# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.100.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr1
xxx.xxx.xx.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
169.254.0.0 0.0.0.0 255.255.0.0 U 1002 0 0 eth0
0.0.0.0 xxx.xxx.xx.62 0.0.0.0 UG 0 0 0 eth0
I've also setup IP FORWARDing and Masquerading this way:
iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
iptables --append FORWARD --in-interface virbr0 -j ACCEPT
All works up to this point. If I want to remote access vtest1 (or vtest2) first I ssh to serv05 and then from there ssh to vtest1. Is there a way to setup a port forwarding so that vtest1 can be accessed directly from the outside world? This is what I probably need to setup:
external_ip (tcp port 4444) -> DNAT -> 192.168.122.50 (tcp port 22)
I know it's easily do'able using a SOHO router but can't figure out how can I do that on a Linux box. Any help form you guys?? Cheers!!
Update: 1
Now I've made ssh to listen to both of the ports:
[root@serv05 ssh]# netstat -tulpn | grep ssh
tcp 0 0 xxx.xxx.xx.197:22 0.0.0.0:* LISTEN 5092/sshd
tcp 0 0 xxx.xxx.xx.197:4444 0.0.0.0:* LISTEN 5092/sshd
and port 4444 is allowed in the iptables rules:
[root@serv05 sysconfig]# grep 4444 iptables
-A PREROUTING -i eth0 -p tcp -m tcp --dport 4444 -j DNAT --to-destination 192.168.122.50:22
-A INPUT -p tcp -m state --state NEW -m tcp --dport 4444 -j ACCEPT
-A FORWARD -i eth0 -p tcp -m tcp --dport 4444 -j ACCEPT
But I'm getting connection refused:
maci:~ santa$ telnet serv05 4444
Trying xxx.xxx.xx.197...
telnet: connect to address xxx.xxx.xx.197: Connection refused
telnet: Unable to connect to remote host
Any idea what's I'm still missing? Cheers!!
Folks,
I am new to using VMware, so please excuse if this is a newbie question.......
How can I netboot a guest Linux virtual machine ?
I'm using VMware server 2.0 running on a Linux host ( Fedora ).
Would appreciate any pointers…..
Cheers !!
S
Hey,
Around two days ago I saw someone working on a computer and alt-tabing to different OSs. Basically he had 3 "screens", one with Fedora, one with Windows XP, one with Mac OSX. How is that possible? I dont think it was a virtual machine.... sounds friggin awesome though.
Hey,
Around two days ago I saw someone working on a computer and alt-tabing to different OSs. Basically he had 3 "screens", one with Fedora, one with Windows XP, one with Mac OSX. How is that possible? I dont think it was a virtual machine.... sounds friggin awesome though.
I have about four or five machines in the Pentium 3-4 era and I'm interested in creating a Linux server comprised of these machines. The server's main purposes would be to host several low-medium traffic websites/services (voice and game), and share terabytes of data on a local network.
I could probably throw together one modern computer as a server and call it a day, but I'm interested in using these machines to do it instead. Where would I get started in this cluster/cloud setup?
I want to use Windows Server 2008 R2 as a host, and load RedHat as a guest OS.
Should I use VMWare, or does Windows have something built in that competes with VMWare?
Anyone know how to modify entries on the host file when it is being marked as read-only? I have tried unchecking "Read-only" but it says "Access is Denied". I'm runnin as the Administrator.
I'm running an install of CentOS 5.5 virtually and for some reason I only have 2 available screen resolutions - 800x600 and 640x480. Does anybody know how I can add some bigger resolutions?
I've had a look in /etc/X11/xorg.conf and it is knows that the graphics card is virtual, but even listing the resolutions that I want fails.
Here is the default screen section -
Secton "Screen"
Identifiew "Screen0"
Device "Videocard0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 24
EndSubSection
EndSection
And here is what I tried adding to SubSection "Display" -
Mode "1024x768" "1280x1024"
I'm trying to create a cron job that uses ssh to login to a remote server and run a script as a different user. I try:
* * * * * source $HOME/.keychain/$HOST-sh && sudo -u $USER $PATH/$SCRIPT
but this doesn't work because there is no -t option specified for ssh. The cron job needs to source the keychain file in order to work without a password, but I'm not sure where to include the -t option for ssh in this instance.
Please provide your tips and best practices for virtualizing SQL Server in VMWare ESX
I am interested in advanced configurations and settings.
Please provide reasoning behind your recommendations
Edit:
Just to clarify, I already have over 70 Virtual SQL servers in separate clusters using an ISCSI equallogic San -
What I am really looking for are those advanced configurations like:
How you configured your disks / RDM's
Do you make use of settings like
Mem.ShareScanGHz - http://communities.vmware.com/thread/143828 -
that are not well documented
I used to have this add-on but now I forgot what it's called. Basically it can track any website's load time, DNS seeking time, time from host to javascript execution and HTML rendering, things like that.
Got any suggestions for such an add-on for Firefox? Thanks.
I've noticed several articles that have claimed that QEMU is slower than VirtualBox (without hardware assistance) but several are years old, and the newest seemed to be from last year.
Is it true that QEMU is slower than VirtualBox?
If so why?
Are there any tricks to close the performance gap?
Some of my host systems do not have virtualization support so I'm especially interested in performance tips that work without the kernel module.
I am just trying to restore a mysql dump. Below are the command and error message.
Can anybody give me some clues how to approach this?
10:54:16 Restoring C:\Users\matcheek\Documents\dumps\Dump20120405-1.sql
Running: mysql.exe "--defaults-extra-file="d:\temp\tmpbvhy4i.cnf" " --host=127.0.0.1 --user=root --port=3306 --default-character-set=utf8 --comments < "C:\\Users\\matcheek\\Documents\\dumps\\Dump20120405-1.sql"
ERROR 2006 (HY000) at line 271: MySQL server has gone away
I am using mysqldump for a large database (several GB) and import the result from a pipe, please see commands below, does it do incremental pipe, or wait until the first one finishes then import? is this a good way of importing large db across servers? I know you can export gz it, then pscp it then import. Quick alternative are welcome
mysqldump -u root -ppass -q mydatabase | mysql -u root -ppass --host=xxx.xx.xxx.xx --port=3306 -C mydatabase
I need to set up an Ubuntu server as a router. However we need to make it wireless and wired. I need a WLAN adapter for the wireless part of the router.
I get my Internet connection on my server through my wireless adapter from my host but it automatically sees it as an Ethernet adapter instead of as a wireless adapter.
Is there any way of making a (virtual) wireless adapter on Ubuntu server 12.04 inside a hyper-v machine?
I am setting up Untangle in a Sun VirtualBox VM. I plan on using this machine as a transparent bridge to filter and monitor traffic on my network. I'm not sure how to configure the network adapters for the virtual machine under the Virtualbox's "Devices" menu so that it will function as a transparent bridge. I guess what I'm asking is, should both adapter 1 & 2 be set as Bridged adapters or what?
Any help is greatly appreciated.
I ssh on remote host but terminal performance is poor. Symbols I am typing are not shown immediately, but with some delay. Sometimes two symbols are shown at one time after delay.
I am trying to ping one of my local host and checking CPU process to see how "Ping of death" attack behaves. I tried to ping my other PC which is in local network with 192.168.44.2 IP Address. I tried this,
ping -l 5000 192.168.44.2
and I got error like this,
ping: -l flag: Operation not permitted
I am on MacOSX Lion. How can I remove this flag so machine can let me ping with preload?
Thanks for any direction!