Veghead's Spell Book
Contents
- Cloaking Spells
- Containment Spells
- Debianicals
- Discworlde
- Perls of wisdom
- Remedies for nuisance
- Spells of the 6th order
- Shellmanship
- Videographical Spells
Containment Spells
Run a docker container, without launching the entrypoint
-
docker run -it --entrypoint '/bin/bash' mycontainer -s
root@6f3eca61s5cf4:/#
Cloaking Spells
Turn an empty partition into an encrypted LUKS device
- cryptsetup -y -v luksFormat /dev/sdbX
Set a passphrase for your LUKS device volume, and name it "mydrive"
- cryptsetup luksOpen /dev/sdbX mydrive
Show information about an encrypted LUKS device
- cryptsetup luksDump /dev/sdbX
- cryptsetup -v status mydrive
Force every sector to be encrypted, and then format it with ext4
- dd if=/dev/zero of=/dev/mapper/mydrive
- mkfs.ext4 /dev/mapper/mydrive
Mount encrypted LUKS volume
- mount /dev/mapper/mydrive /mnt
Unmount encrypted LUKS volume and secure it
- umount /dev/mapper/mydrive
- cryptsetup luksClose mydrive
Add subjectAltName (SAN) to home-made certs in OpenSSL.
These days, the Common Name (CN) is not the preferred way of matching certs to websites. Instead, the x509v3 option "Subject Alternative Name" is used. You can force this using the openssl.cfg file. From OpenSSL v1.1.1 you can add it directly on the command line instead. e.g.:
-
openssl req -new -subj "/C=US/CN=example.com" \ -addext "subjectAltName = DNS:www.example.com" \ -newkey rsa:4096 -keyout site.key -out site.req
Even if your CN is valid, some browsers (e.g. Chrome) can whinge with a ERR_CERT_COMMON_NAME_INVALID error, if there is no SAN.
Good description here.
Videographical Spells
Extract 40 seconds starting at 4:40 from biglongmovie.avi into clip.avi - recoding as xvid.
- ffmpeg -ss 00:04:40 -t 40 -i biglongmovie.avi -sameq -isync -acodec copy -vcodec libxvid -vsync 0 clip.avi
On a mac, take a divx and convert to something iMovie likes
- /Applications/ffmpegX.app/Contents/Resources/ffmpeg -i dixmovie.avi -sameq -vsync 0 happyimovie.mov
Convert divx to DVD style MPEG
- mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=dvd -vf scale=720:576,harddup -srate 48000 -af lavcresample=48000 -lavcopts vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:keyint=15:aspect=16/9:acodec=ac3:abitrate=192 -ofps 25 -o dvd.mpg mymovie.avi
Create a DVD image from an MPG
-
dvdauthor -o dvdimage -x dvd.xml
Example xml files:
Burn a DVD image in Linux/un*x
- chmod 500 AUDIO_TS VIDEO_TS; chmod 400 VIDEO_TS/*; growisofs -dvd-compat -Z /dev/scd0 -dvd-video .
Transcode a movie to a Roku-friendly MP4
- ffmpeg -i my_divx_or_xvid_or_whatever.avi -vcodec libx264 -acodec libfaac -ac 2 -ar 44100 -ab 128k -b 1000k -vpre medium my_divx_or_xvid_or_whatever.mp4
Extract an MPEG2 from a DVD image quickly
- mencoder dvd://1 -ovc copy -oac copy -of mpeg -o first-title-show.mpg
Perls of wisdom
Search and replace a regular expression in a bunch of files, keeping backups
- perl -pi.bak -e 's/oldthing/newthing/g' *
Remedies for nuisance
Prevent tar from including "._" files on MacOS
-
Set COPYFILE_DISABLE=1 in the environment e.g.
COPYFILE_DISABLE=1 tar zcvpf myarchive.tar.gz files
Prevent the annoying "... can automatically configure your Mac" Device Enrollment pop-up from appearing on Big Sur
- sudo touch /var/db/ConfigurationProfiles/Settings/.cloudConfigProfileInstalled
Do not be tempted to disable Signed System Volume (SSV) support!
Disable SIP (System Integrity Protection) on MacOS
- Boot into recovery mode (hold down Cmd-R during boot)
- Go to Utilities->Terminal
- csrutil disabled
- Reboot
Disable MacOS's obnoxious "The default interactive shell is now zsh." message
- Add export BASH_SILENCE_DEPRECATION_WARNING=1 to $HOME/.bash_profile
- Or install a much newer vesion of bash from homebrew: brew install bash
Shellmanship
Find all unique jpegs
Find all unique jpegs in your filesystem (from Seb).
- find / -type f -iregex '.*jpe*g$' | xargs sha1sum | sort | uniq -w 40 | cut -d " " -f3
MacOS tar and resource files
Prevent tar from including resource files with "._" (dot underscore) prefixes when creating archives.
- export COPYFILE_DISABLE=true
MacOS file resource magic
Extract an icon as a resource script
- DeRez -only icns IconFiles.icns > Icon.rsrc
Add a custom icon, stored as a resource script, to an existing file
-
Rez -append Icon.rsrc -o MyApp.pkg
SetFile -a C MyApp.pkg
Hide a file extenstion
- SetFile -a E MyApp.pkg
MacOS equivalent of strace
- dtruss -d /path/to/executable/you/want/to/examine
Discworlde
Making Hybrid CDs/DVDs on a mac
This will build an ISO image that will appear as a Windows CD on Windows machines and a Mac CD on Macs. We assume the current directory contains all the files you want to burn. In this case the Windows autorun files are hidden from the Mac and the Mac files are hidden from Windows.
- hdiutil makehybrid -iso -hfs -joliet -hide-hfs '{AutoRun.bmp,AutoRun.exe,AutoRun.inf,AutoRun.ini,Docs,Prerequisite,ReadMe,System32,System64,Tools}' -hfs-openfolder . -hide-joliet '{.DS_Store,.background,Applications,MyApp.app}' -hfs-volume-name 'My CD' -o ../NewDiskImage.iso .
Fix DiskUtility
Make DiskUtility stop lying and let you do what you want to do with your own partitions.
- defaults write com.apple.DiskUtility DUDebugMenuEnabled 1
Debianicals
SysV service maintenance
- update-rc.d -f SERVICENAME remove
- update-rc.d SERVICENAME start 20 2 3 4 5 . stop 80 0 1 6 .
- update-rc.d SERVICENAME defaults
Add missing key to APT to fix apt-get update
- gpg --keyserver wwwkeys.eu.pgp.net --recv-keys XXXXXXXXXXXXXXXX
- apt-key add /root/.gnupg/pubring.gpg
- apt-get update
Spells of the 6th order
Add an address to an interface
- ip a a fe80:ab7f:16d2:1::1 dev eth0
Add a /64 subnet to an interface
-
ip r a fe80:ab7f:16d2:1::/64 dev eth0
This is useful if you've been given a /48 from your ISP. In this (fictional) case, the block was fe80:ab7f:16d2::/48
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