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location Virginia
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visits member for 5 years, 7 months
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Nov
10
comment How much SWAP space on a high memory system?
@warren: I have Tomcat instances, each in excess of 3GiB, yet using no swap (and one is using hugepages, and thus can't be swapped). Not sure what you're talking about.
Nov
7
comment Long Distance Networking Options
When running your PVC conduit, please remember to install extra pull strings.
Oct
28
comment How to monitor internet traffic on a Linksys E3000 router
There are third-party firmware images for your router which will give you that functionality (if it isn't already built in). I'm sure the folks on SuperUser will know more. You can "flag" your own question for migration if you'd like.
Oct
14
comment Cutting down network noise on an industrial control network
You don't even necessarily need routing if your control PC (operator interface) can do VLAN trunking to be on both VLANs. Or if the operator interface only needs to be on the control VLAN.
Oct
13
comment Accurate, Unspoofable Time Source
Setting up your own atomic clock is not hard, you can just go buy one (look for a "frequency standard"). Its expensive, though.
Oct
5
comment Computer Networks bonus: find MTU less than 1500
@Stefan: I'm somewhat surprised you can't find one anywhere, though I suppose the last time I had one (temporarily) in a network I was using, it was painful. A lot of people configure firewalls to break PMTUd, yet leave it enabled on their servers. Or at least did back in the early 2000s.
Oct
4
comment Computer Networks bonus: find MTU less than 1500
You probably want to do two pings—one with a fairly small packet and one with the larger (1500 byte packet), and see which hosts only respond to the small one. Two pings will be much quicker than a traceroute.
Oct
4
comment Computer Networks bonus: find MTU less than 1500
PPPoE (e.g., DSL lines) is a good place to try.
Oct
4
comment Transfer 10TB of files from USA -> UK datacenter
rsync restart time scales with number of files (mainly from stat time, in my experience), not with total data. I would expect no significant wait (several minutes at most). Though my experience with rsync tops at a little under 5TB.
Sep
30
comment Setting the From header makes mail() take a long time to send
This probably isn't really a programming question, as I think its far more likely due to your server's MTA configuration. I'm going to vote to send this to Serverfault, because I think they're much more likely to know how to fix this.
Sep
30
comment SSH connection keeps crashing
Its probably firewall related. You wouldn't happen to be dropping ICMP, in particular ICMP fragmentation needed messages, would you? (BTW: this question will hopefully be moved to Serverfault—where it is on-topic—soon. You don't need to do anything, the moderators here will take care of it)
Sep
27
comment how to investigate real problem with TX packet drops in linux?
@Sergey: You're doing TCP, so you're supposed to adjust your delays based on the ACKs. As for the kernel interface, ifconfig gets it (on Linux) from /proc/net/dev. You can also use the more modern /sys/class/net/venet0/statistics/*
Sep
27
comment how to investigate real problem with TX packet drops in linux?
@sashang: I'm pretty sure there is no PHY, that v standing for virtual or virtualized. I would guess dropped in this case means that a buffer filled up (e.g., sending faster than the hypervisor can handle)
Sep
15
comment Odd POTS fax issue
OK, they all have separate lines (wires) to the PBX, correct? If so, it does sound like something is up with the PBX. Maybe it gets confused when an incoming fax rings all lines and shortly after one of the fax machines wants an outgoing line. Sounds like you'll have to deal with the PBX, unfortunately. Or just make everyone send with one fax machine only.
Sep
15
comment Check file integrity while writing
@Julien Vehent: Data isn't really piped through ionice. It just does an ioprio_set syscall, then an exec to call the real program. ionice is just like nice, except it changes the IO priority instead of the CPU priority.
Sep
15
answered OpenVPN client without redirect-gateway doing triangular routing and IP spoofing not working on Ubuntu
Sep
15
comment Odd POTS fax issue
When you say they're on the same line, what do you mean? A POTS line can only have one phone call at a time. Do you mean one telephone number? If you actually mean one line, then of course multiple things attempting to dial on the same line are going to break.
Sep
15
comment Can 3G networks be packet sniffed / analyzed?
$5mil is way more than it'd take, real number is probably several thousand, at most. Many of the ciphers used have been broken; the chipsets to receive cell signals are very cheap; etc.
Sep
15
comment portable unix way to join strings with separator
Considering OP wants to join parameters, that'd be perl -E 'say join(shift, @ARGV)' -- delim str1 str2 str3 ... The perl one-liner you've posted doesn't actually do anything (well, it changes $_, but that isn't passed into or out of the one liner). You probably wanted to pass -p as well.
Aug
4
comment Fastest/scalable way to serve static files?
@user658911 let us continue this discussion in chat