Archive for the ‘Power User’ Category
Posted by jpluimers on 2020/06/11
Not being a proficient Linux programmer, I wondered what other means than learning gdb intrinsics I had to get more information about a segmentation fault.
A while back, pip list 2> /dev/null would cause a segmentation fault on my system (see [WayBack] Bug 1084812 – [aarch64] IPv4 DNS leading to segfaults).
It turns out that LD_PRELOAD was my friend (like TERM=xterm was a friend before):
LD_PRELOAD=libSegFault.so pip list 2> /dev/null
It indicated that the problem was in libc, which on opensuse is implemented by glibc.
This meant that the originally diagnosed problem was already accurately describing the symptoms.
Searching for glibc libSegFault.so didn’t reveal many useful links, so I’ve included the one making most sense to me here:
The cool thing: most of the links above come from [WayBack] segmentation fault – Can you get any program in Linux to print a stack trace if it segfaults? – Server Fault which I found when searching for linux find segmentation fault stack trace
That link explains both the LD_PRELOAD steps and gdb steps (:
An alternative is to use gdb directly: [WayBack] command line arguments – How do I run a program with commandline args using gdb within a bash script? – Stack Overflow:
gdb -ex=run --args pip list
--jeroen
Posted in *nix, C, Development, gcc, Linux, Power User, Software Development | Leave a Comment »
Posted by jpluimers on 2020/06/10
Sometimes you are stuck. Then this often helps, even outside the music industry:
[WayBack] Oblique strategies – defeat creative block: Draw random Oblique Strategy cards to break through creative block.
These are disruptive which is the whole point being stuck.
Obey the first and only rule: pick the first card and apply what it says.
- Do NOT fall for the urge to draw multiple cards.
- Do NOT make a list of all cards then choose from it.
Both above failures kill the randomness of the above strategy.
More on them at [WayBack] Oblique Strategies – Wikipedia
Via:
–jeroen
Read the rest of this entry »
Posted in Agile, Development, LifeHacker, Power User, Software Development | Leave a Comment »
Posted by jpluimers on 2020/06/10
A while ago, I had to execute a series of aliases of which the names were stored in an array. A simple for loop with en eval call did the job.
Then I found out there are at least two more ways of evaluation in bash, so here are just a few links giving me a head start if I ever dig this up again:
Note that looping over parameters is different than over an array: [WayBack] Loop through an array of strings in Bash? – Stack Overflow
ou can use it like this:
## declare an array variable
declare -a arr=("element1" "element2" "element3")
## now loop through the above array
for i in "${arr[@]}"
do
echo "$i"
# or do whatever with individual element of the array
done
# You can access them using echo "${arr[0]}", "${arr[1]}" also
Also works for multi-line array declaration
declare -a arr=("element1"
"element2" "element3"
"element4"
)
–jeroen
Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development | Leave a Comment »
Posted by jpluimers on 2020/06/09
This is part of a bash alias where I had to use quadruple backslash in order to escape it for sed:
# The sed with quad //// is to prevent 'unterminated substitute in regular expression':
alias x='... | sed "s/=.*/ \\\\/"'
This is needed because bash will escape \\\\ into \\ which sed then escapes to \.
The easiest way to find this is to replace the sed with echo to see the expansion.
References:
–jeroen
Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, sed, Software Development | 2 Comments »
Posted by jpluimers on 2020/06/08
Cool:
use command:
fsutil hardlink list MyFileName.txt
It lists all hardlinks to file with name MyFileName.txt.
Source: [WayBack] hardlink – How can I find hard links on Windows? – Super User
More information at [WayBack] Fsutil hardlink | Microsoft Docs on
fsutil hardlink create <NewFileName> <ExistingFileName>
fsutil hardlink list <Filename>
–jeroen
Posted in Power User, Windows, Windows 10, Windows 7, Windows 8, Windows 8.1 | Leave a Comment »
Posted by jpluimers on 2020/06/08
For a really nice overview of most basic and intermediate usage of ssh, read [WayBack] SSH Essentials: Working with SSH Servers, Clients, and Keys | DigitalOcean.
It is large (printed to PDF it is 30+ pages in either A4 or Letter format) but well worth reading as it covers a lot in manageable bits.
Does it mean I won’t write about ssh again?
I will continue, as most of my blog posts are relatively short highlighting a small thing at a time (that is how I learn best, hopefully some of you do as well).
It does not explain really advanced stuff (like ProxyCommand), so here is a start of things I want to learn more about:
–jeroen
Posted in *nix, *nix-tools, Power User, ssh/sshd | Leave a Comment »
Posted by jpluimers on 2020/06/05
On my research list: find out why a Local Administrator on Windows 10 Professional x64 did get “access denied” just when executing wmic:
–jeroen
Posted in Power User, Windows | Leave a Comment »
Posted by jpluimers on 2020/06/05
If you want to harden your ssh server, read at least [WayBack] sshd_config – How to configure the OpenSSH server | SSH.COM.
After that use some ssh tools to check your config from the outside world. They work in a similar way as the TLS/SSL/https scans from Source: SSL Server Test (Powered by Qualys SSL Labs) or these console based scans and documentation references:
Simiarly for SSH:
Then read further on more in depth SSH topics around key management:
–jeroen
Posted in Encryption, Hashing, https, HTTPS/TLS security, OpenSSL, Power User, Security, testssl.sh | Leave a Comment »
The Wiert Corner - irregular stream of stuff 