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Posted by jpluimers on 2020/01/13
From a while back: [WayBack] ⚡Julia Evans⚡ on Twitter : made a perf cheat sheet from @brendangregg’s fantastic brendangregg.com/perf.html you can print it at …
References:
The latter has a lot of examples and even more explanation all around the below picture.
–jeroen
Posted in *nix, *nix-tools, Development, Linux, Power User, Profiling-Performance-Measurement | Leave a Comment »
Posted by jpluimers on 2019/12/23
For my link archive: [WayBack] imagemagick – Command line convert webp to jpg? – Unix & Linux Stack Exchange
All these archives contain both the
cwebpanddwebpprecompiled executables, along with thelibwebp.alibrary and C headers (the latter allowing you to add WebP encoding or decoding to your own programs).
cwebp — Compress an image file to a WebP filedwebp — Decompress a WebP file to an image file–jeroen
Posted in *nix, *nix-tools, Development, Encoding, Google, GoogleWebP, Image Editing, Power User, Software Development, The Gimp, WebP | Leave a Comment »
Posted by jpluimers on 2019/12/20
Cool: Magic SysRq key – Wikipedia
The magic SysRq key is a key combination understood by the Linux kernel, which allows the user to perform various low-level commands regardless of the system’s state. It is often used to recover from freezes, or to reboot a computer without corrupting the filesystem.[1] Its effect is similar to the computer’s hardware reset button (or power switch) but with many more options and much more control.
Sometimes reading fluffy fluff posts teaches you new things, so be sure to read this one:
[WayBack] I just got trolled by my cat, hard. Last night i left my linux laptop open and running while watching TV in the other room. I came back to find Marley … – Stephen Shirley – Google+
…
I started looking through the kernel logs from last night, to see if there was any indication of the issue starting. And then i saw it. One innocent line that said:
Dec 18 21:26:52 x240 kernel: [373001.156356] sysrq: SysRq : Emergency Remount R/O
The fluffy dumbass had somehow hit the Sysrq [0] key combo to mount all filesystems read-only. This is an old, low-level when-all-else-fails facility for dealing with an linux unresponsive system, and fluff-for-brains Marley had somehow hit alt+fn+s+u.
Sigh.
Via: [Archive.is] I just got trolled by my cat, hard. Last night i left my linux laptop open and running while watching TV in the other room. I came back to find Marley … – Kristian Köhntopp – Google+
–jeroen
Posted in *nix, *nix-tools, Keyboards and Keyboard Shortcuts, Linux, Power User | Leave a Comment »
Posted by jpluimers on 2019/12/16
The answers at [WayBack] CHMOD – Applying Different Permissions For Files vs. Directories – Server Fault describe various ways to do this. Depending in why/when you want to change them you’d probably favour different ones, so be sure to read the answers.
I mostly use these combinations:
find . -type d -exec chmod 700 {} \; find . -type f -exec chmod 600 {} \;
and
find . -type d -exec chmod 775 {} \; find . -type f -exec chmod 664 {} \;
And since I forget how to do ocatal too often:
commonly used permissions:
Permission COMMAND --------- ------------------ rwxrwxrwx chmod 777 filename rwxrwxr-x chmod 775 filename rwxr-xr-x chmod 755 filename rw-rw-rw- chmod 666 filename rw-rw-r-- chmod 664 filename rw-r--r-- chmod 644 filenamepermissions are divided into 3 divisions. The first rwx is for the owner. The next 3 is for the group. The last 3 is for everyone else.
rwx------ owner permissions - read, write, executable ---rwx--- group permissions - rwx ------rwx other permissions - rwx
–jeroen
Posted in *nix, Power User | Leave a Comment »
Posted by jpluimers on 2019/12/03
Many unix tools that report sizes in bytes can convert them to either IEC or SI readable formats.
For github.com/jpluimers/btrfs-du/blob/master/btrfs-du I wrote about last week, I also wanted that kind of behaviour. So I did some research and came up with the code and test cases below.
Note that depending on the bitness of your system, bash integer numeric values are limited in size; see [WayBack] What is the maximum value of a numeric bash shell variable? – Super User.
So I wrote a small
bashscript for that too, which needed also gave me the opportunity to show how a perpetual while loop as explained by [WayBack] bash – “while :” vs. “while true” – Stack Overflow.Two things that always bite me with these short scripts are expressions (done through [WayBack]Arithmetic Expansion) and comparisons (through[WayBack] Other Comparison Operators).
The IEC suffixes contain one extra i to indicate binary and – next to the ISO notation that were already ISO defined – made it into the ISO 80000 standard since 2008. Here is a comparison list from [WayBack] Binary prefix – Wikipedia:
Most tools nowadays default to binary IEC suffixes for byte sizes, though disk manufacturers still use SI suffixes because, well then they appear bigger but aren’t. Just for comparison, look at the numbers from [WayBack] File size – Wikipedia and [WayBack] IEC and SI Size Notations – AN!Wiki where I got the test cases from:
Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development | Leave a Comment »
Posted by jpluimers on 2019/11/26
Hopefully I’ve been able to integrate some of the ideas in the links below in github.com/jpluimers/btrfs-du/blob/master/btrfs-du
One of the features I wanted there was to be able to add optional switches like --raw, --iec or --si to it similar to what as the btrfs qgroup show subcommand has.
It seems possible with bash, but it is not trivial, at least not for me as a non-frequent bash user, so here are some links to get me started:
In retrospect, other languages than bash might have been a better choice for a script like that (:
–jeroen
PS, some btrfs references:
Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development | Leave a Comment »
Posted by jpluimers on 2019/11/25
In case I ever need to view the archived /var/adm/backup/rpmdb files again: [WayBack] rpm – Suse: Restore Packages List from /var/adm/backup/rpmdb/Packages-20160323 .gz – Server Fault
–jeroen
Posted in *nix, Power User, rpm | Leave a Comment »
Posted by jpluimers on 2019/11/20
One day, on a legacy Linux system, logrotate managed to skip some files in the middle of a sequence in /var/log.
Since I didn’t have time to sort out the cause (the system was being phased out), I used this to compress the rest of the log-files (dated in 2017):
sudo -u bash
pushd /var/log
ls | grep -vw xz | grep "\-20......$" | xargs -L 1 ls -alh
After that you can execute this in the same directory:
ls | grep -vw xz | grep "\-20......$" | xargs -L 1 time xz
It skips any xz files and includes only files in the year 2017.
I occasionally tracked progress with this:
ls -alh /var/log/ | grep -v xz | less
That got back a few gigabytes of disk space, just enough to help me migrate the system away.
–jeroen
Posted in *nix, *nix-tools, bash, logrotate, Power User | Leave a Comment »
Posted by jpluimers on 2019/11/15
When you see messages like below in your bind named.d logs then you’ve a Jekyll and Hyde network config: part of it says it supports IPv6, but in reality doesn’t as “2001:500:127::30” is the IPv6 of the generic TLD servers.
In my case a brain-dead TP-Link switch.
04-Dec-2016 13:05:48.008 lame-servers: network unreachable resolving 'c.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.008 lame-servers: network unreachable resolving 'd.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.008 lame-servers: network unreachable resolving 'e.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.008 lame-servers: network unreachable resolving 'f.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.008 lame-servers: network unreachable resolving 'g.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.009 lame-servers: network unreachable resolving 'h.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.009 lame-servers: network unreachable resolving 'i.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.009 lame-servers: network unreachable resolving 'j.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.009 lame-servers: network unreachable resolving 'k.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.009 lame-servers: network unreachable resolving 'l.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
04-Dec-2016 13:05:48.009 lame-servers: network unreachable resolving 'm.gtld-servers.net/AAAA/IN': 2001:500:127::30#53
...
04-Dec-2016 13:24:13.500 lame-servers: network unreachable resolving './NS/IN': 2001:500:2f::f#53
A temporary solution is to run bind named.d in -4 mode (see examples for RHEL, CENTOS and OpenSuSE in the links below), but the actual solution is to get IPv6 working properly.
–jeroen
Posted in *nix, bind-named, Linux, Power User | Leave a Comment »
Posted by jpluimers on 2019/11/08
After all these years in the field, I still learned new tricks from [WayBack] 20 Cool Command Line Tricks for Windows and macOS which I have rephrased:
Windows
1) View installed drivers: [WayBack]
driverquery2) Watch Star Wars in ASCII: [WayBack]
telnet towel.blinkenlights.nl…
3) Save folder trees to disk:
tree(I had totally forgotten about this, probably because it leaves out a lot of directories and files)…
5) Show your Wi-Fi password [WayBack]
netsh wlan show profile SSID key=clear(replaceSSIDwith your network name; usenets wlan show profileto view the network names)…
7) Check your laptop’s battery health: [WayBack]
powercfg /batteryreportwhich will be in ” and hit Enter to generate the report, then%HOMEPATH%\battery-report.html8) View your Windows license key:
wmic path softwarelicensingservice get OA3xOriginalProductKey[WayBack]…
Mac OS X / macOS / however it is called now
1) Change the default screenshot type: [WayBack]
defaults write com.apple.screencapture type JPG(you can also useJP2(for JPEG2000),PNG,TIFFand others)2) Get your Mac to speak to you: use
say3) Add a message to the login screen:
sudo defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "your new text on the logon window"[WayBack]4) Play Tetris and other classics: start
emacs, then pressEscfollowed byX, type intetris,pong,snakeorsolitaire(to exitemacs, pressCtrl–Xfollowed byCtrl–C). There are [WayBack] more emacs games.5) Get a dictionary definition: run
curl dict://dict.org/d:word(wherewordis what you are after) which uses the [WayBack] dict protocol6) Keep macOS awake: [WayBack]
caffeinateoptionally followed by a-t##parameter where##is the number of seconds to not sleep.7) Show hidden files:
defaults write com.apple.finder AppleShowAllFiles -bool TRUE; killall Finderor use thisAppleShowAllFilesscript which I had forgotten about writing in the first place.…
10) Add Spaces to the Dock:
defaults write com.apple.dock persistent-apps -array-add ‘{”tile-type”=”spacer-tile”;}’; killall Dockrunning the command as many times as you want spaces. To get rid of a space you’ve added, just drag them to the Trash.
–jeroen
via: [WayBack] 20 Cool Command Line Tricks for Windows and macOS http://flip.it/SvcQlu – Joe C. Hecht – Google+
Posted in *nix, *nix-tools, Apple, cURL, Power User | Leave a Comment »
The Wiert Corner - irregular stream of stuff 