7,697 reputation
12253
bio website tltech.com
location United States
age 35
visits member for 5 years, 6 months
seen Dec 11 at 18:55

{{Hacker}}

I own a small, successful security consulting business. But by day I work for a really big company, doing really big things.

Nothing I write here represents the views of my employer, nor does it reflect any proprietary or confidental knowledge. In fact, practically all of it was written before I even started working there, so don't get too excited.


Jan
4
comment How can I add the “noatime” flag to my / filesystem without a reboot
With many versions of mount you can omit either the device or the mount point (your choice) and it will lookup the other.
Jan
3
comment linux procfs file times
Well, actually - I can tell you with certainty that your first paragraph is false. The proc filesystem type is not a real filesystem, and entries aren't "created" in response to system events the way they are, say, in udev. Instead, the OS responds to queries (e.g. file and directory access) by synthesizing and returning the correct data on-the-spot. It's not so much an object as it is an API. It may cache results, but it never creates an actual in-memory or on-disk file structure anywhere.
Nov
29
comment Use IPtables or null route for blacklisting about 1 million IP addresses?
@pQd after previous failures with iptables et al., I implemented a solution in apache using a RewriteMap with Berkeley database. But my my fastest mechanism using iptables in a loop loaded about 100 rules per second, while iptables-restore did the whole set in about 4 seconds. This is on a top-of-the-line desktop computer. The RewriteMap mechanism has an undetectably low impact on performance.
Nov
28
comment Use IPtables or null route for blacklisting about 1 million IP addresses?
@pQd - Yes, and not even by a small margin. Adding 1M rules 1 at a time takes about 6 hours, while iptables-restore is almost immediate.
Nov
28
comment Use IPtables or null route for blacklisting about 1 million IP addresses?
This is a very good approach. Obviously it requires a bit of processing to maintain, but it's the right idea, I think.
Nov
28
comment Use IPtables or null route for blacklisting about 1 million IP addresses?
Converting the client's server architecture to BSD isn't really an option. Thinking out of the box at least, though.
Nov
26
comment Use IPtables or null route for blacklisting about 1 million IP addresses?
As far as I've seen, ipset tops out at 65k IP addresses. Is there any set type that can handle 1M entries?
Nov
2
comment How to keep cron from stampeding?
Instead, just have cron run a single script that executes all your commands in turn. In fact, it's such a common need that there's a standard script called run-parts that ships with most cron installations to do specifically that. See @AndrewSchulman's answer.
Oct
25
comment How do concurrent filesystems work?
@KaitlynMcmordie Disks have to keep track of which blocks are used and which blocks are free separately from where they track which files are using which blocks. It's a performance thing. If you've got space marked as allocated that doesn't match a file or worse, used space marked as free, then that's a problem.
Oct
24
comment How delete the content of a directory in Centos
Note that this doesn't hidden files/directories within MYFOLDER
Sep
20
comment SSH session logging
This is people SSHing from their own workstations into various computers owned by people all over the world. So like I said, remote logging simply isn't a possiblity; it all has to be on the workstation.
Sep
20
comment Development HTTP server with fastcgi support
It's the configuration file I was hoping to avoid.
Sep
18
comment Convert ext4 partition to NTFS
You can actually convert in-place from ext2/3/4 to btrfs, and then roll-back to ext if you want. It does this setting up the btrfs structures in the free space of your ext filesystem, so your drive can be formatted with both at the same time.
Sep
8
comment Linux = Is there something like a “Java Shell” instead of other linux shells?
There's a mighty big difference between using java as your command shell and using java as a scripting language.
Sep
8
comment Bash variable assignment using another variable as part
Also works within quotes: FILENAME="${DB}_$(date +%s)" if you want to embed stars or spaces or something.
Sep
8
comment NginX & PHP-FPM, random 502
Aside from the answers already given, check for situations where a PHP request is making another PHP request (e.g. via CURL) to the same web server. Doing so can be disastrous.
May
26
comment How Often Do Windows Servers Need to be Restarted?
The 32-bit timer issue is valid, but it's an issue that individual software vendors need to carefully avoid in their own code. Windows is no longer susceptible to failures related to this timer (as it was in the past), but if you have software installed that does not account for timer rollback, then it can cause unanticipated effects.
May
9
comment setting up subdomains on nginx
@Ran: Looks about right.
May
9
comment PHP-based emailer
@Zakman411: See additional comments
May
9
comment setting up subdomains on nginx
Each server { } section should have its own location / { } clause. They won't conflict.