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Director of Emerging Technology at BlackMesh Managed Hosting, longtime Linux aficionado, sometime Drupal developer (and d.o sysadmin), and occasional filesystem tinkerer.


Aug
24
comment How can I figure out if port 25 is blocked on my network?
John: "filtered" means that no response was received from the server. "Closed" means a TCP RST was received. The former usually indicates that a firewall has blocked the connection (as they rarely issue RSTs for their "deny" rules), while the latter typically indicates that there really is nothing listening on that port, albeit with the caveat that, with a bit of effort, a crafty net.admin can completely mess up that set of assumptions.
Aug
24
comment How can I figure out if port 25 is blocked on my network?
Slick! You can even specify a port with "-p", so it'd be "tcptraceroute -Tp 25 mydomain.tld" in this case. Thanks for the pointer.
Aug
17
comment Remotely view or logon as another user
First off, this is just patently wrong-headed. If you're the administrator, you can already impersonate someone with impunity, either by logging a message of any kind, or, if that's not sneaky enough, installing a driver that can do even scarier (and even harder-to-trace) things. Nothing the OQ is asking for is impossible at a technical level. Whether it's advisable, or violates ethics standards, or is more difficult than other potential solutions--those are separate questions that deserve proper airing. Simply saying, "sorry, nope, it's impossible," is neither helpful, nor even correct.
Aug
6
comment Vim Pattern replace
Try using a different delimiter for clarity, since you have "/" in your pattern: "%s#<created>\n\s*\w*@\w*\n</created>#newstring#".
Aug
5
comment change directory automatically on ssh login
It's possible, just probably not advisable. Something like replacing ssh with a small shell script or alias that passes the host name as a variable to be exported (a la "ssh -t user@host 'export connhostname=host; bash --login'"). But you're starting to get into very strange territory, indeed. Perhaps a better question is, WHY do you want this behavior?
Aug
5
comment How can I add more than 255 machines to a single Class C network?
In the original classing system, the two high-order bits determine the Class of the address. Having a netmask of 255.255.255.0 makes it Class C-sized, but it doesn't make it Class C.
Aug
5
comment Date of Recent RAM Upgrade (Optiplex 745 w/ XP Pro SP3)
Confirming, the BIOS should have a log event about it. I believe there's a tool to view/clear those log messages without rebooting for Dells, but if not, the BIOS setup screen accessible on bootup should have the option for which you're looking.
Jul
30
comment Is it risky to have a database server and a web server on the same machine?
I don't think anyone's saying that a two-box solution isn't safer. However, the question was whether that risk was, to quote the question, "big". The answer is obviously going to depend on circumstances--I wouldn't run an Internet-facing banking site on a single machine, for example. But a properly-locked down Web server, once compromised, should have no more or less access to its database server than it did before being compromised, and that principle is independent of whether the solution is on two machines or one. If that's not true, it's time to re-architect the system.
Jul
29
comment Forcing HTTPS from HTTP (Apache)
If you want to use mod_rewrite here, you should add the "QSA" flag. It'd be simpler to use mod_alias, however. I've posted an answer modified as such. It's also not a good idea to specify the non-SSL host's DocRoot as the SSL host's DocRoot; if someone gets past your Redirect, they're now browsing the SSL site without SSL. Finding an appropriate empty directory is left as an exercise to the reader, or you can add a <Directory /> stanza inside the non-SSL VHost with "deny from all" or similar if you'd prefer.
Jul
29
comment CPU load on CentOS Plesk server between 50-100% but processes only add up to around 10%
Load also includes time spent in uninterruptable sleep. One common source is NFS mounts. Got any of those? Separately, you never really mentioned--is the box responsive during all of this?
Jul
25
comment MySQL goes away when traffic volume spikes
On the off chance you haven't forgotten that you ever asked this question, or in case someone finds this page via a search, the most likely candidate for an answer, given your reply in this comment, is that you've got hanging MySQL connections that are clogging up the database server. Enforcing a wait_timeout or similar may be enough to mask the problem, but the real solution will be using SHOW PROCESSLIST and some detective work to figure out what piece of broken code is keeping the connection(s) open.
Jul
23
comment Why is there less latency on loopback than on a carp interface?
A packet sent to an on-box address, whether addressed through lo or an e{th,n} port, never hits the hardware in Linux, regardless. I can't speak authoritatively with regards to BSD, though.
Jul
22
comment Computer controlled winch
You'd still need some way to turn on the exhaust fan, though.
Jul
22
comment Computer controlled winch
I'd disagree; this is a pretty common topic in the sysadmin world--environmental monitoring and what the hell to do when said monitor goes off, other than to panic. We're in an N+2 facility now, but many people aren't, and a good backup plan is worth its weight in (not-dead) servers, no matter where you are.
Jul
21
comment HowTo install cURL on ISS 7, PHP5 and Win Server 03
Ah. In that case, check serverfault.com/questions/141091/how-to-install-php-curl-on-iis .
Jul
21
comment iptables redirected port 80 to 8080 - How to disallow direct access to port 8080?
Is there a reason not to simply run your Tomcat server on port 80 natively?
Jul
21
comment Stdout/stderr redirects in start-stop-daemon
Yep, so just replace the last two lines with: NCMD="exec $DAEMON $DAEMON_ARGS";start-stop-daemon -Sbmv --pidfile $PIDFILE --chdir ${DAEMON_DIR} --exec $DAEMON --startas /bin/sh -- $NCMD 1>>$APPLOG_FILE 2>>$ERRLOG_FILE
Jul
21
comment MySQL goes away when traffic volume spikes
Can you post some of the configuration and profiling information I requested in #161286? It'll really help us answer your question.
Jul
19
comment What's the most efficient way to set up an a remote desktop server with Linux?
Forwarded X is going to be faster than VNC, if you're bandwidth-constrained, in almost all circumstances.
Jul
19
comment What ports are needed for a Windows XP client to acces a folder on a SAMBA server?
It'll work like a charm. Only thing to be aware of is, if this is traversing the public Internet, there's a fair chance tcp/445 might be blocked by one of your ISPs on either end.