sudo editör /usr/share/applications/defaults.list 

editör = kullandığınız metin editörü
Xfce' de burada bir liste mevcut mu bilmiyorum. Eğer varsa, içeriğini isteğinize göre düzenleyebilirsiniz.
Daha kolay bir yöntemi varsa, bilen arkadaşlar yardımcı olacaktır.

Malesef mevcut değil. Her seferinde sağ tıklayıp dosyaları o şekilde açıyorum. Genelde sağ tıkla varsayılan atadıktan sonra bir sıkıntı olmuyor; ama bazen bir program kurduğunuzda o programın gerekliliği olan bazı uygulamalar varsayılanları değişitirebiliyor. Geçen gün mousepad bir dosya türüne varsayılan olarak atanmış bende dikkat etmeden açınca sistem tıkandı.

/home/Kullanıcı_Adı/.config/mimeapps.list

Bu şekilde bir dosya mevcut mu?

Evet bir dosya var. Bu dosya üzerinden mi istediğim dosya türüne göre değişiklikler yapacağım.

Evet, bu dosyayı düzenleyebilirsiniz.

[Default Applications]
application/rtf=abiword.desktop
application/x-abiword=abiword.desktop
text/abiword=abiword.desktop
text/richtext=abiword.desktop
text/rtf=abiword.desktop
text/x-abiword=abiword.desktop
text/x-xml-abiword=abiword.desktop
x-content/blank-bd=brasero-nautilus.desktop
x-content/blank-dvd=brasero-nautilus.desktop
x-content/blank-cd=brasero-nautilus.desktop
x-content/blank-hddvd=brasero-nautilus.desktop
application/x-dia-diagram=dia.desktop
image/bmp=eog.desktop
image/gif=eog.desktop
image/jpeg=eog.desktop
image/jpg=eog.desktop
image/pjpeg=eog.desktop
image/png=eog.desktop
image/svg+xml=eog.desktop
image/svg+xml-compressed=eog.desktop
image/x-bmp=eog.desktop
image/x-gray=eog.desktop
image/x-icb=eog.desktop
image/x-ico=eog.desktop
image/x-pcx=eog.desktop
image/x-png=eog.desktop
image/x-portable-anymap=eog.desktop
image/x-portable-bitmap=eog.desktop
image/x-portable-graymap=eog.desktop
image/x-portable-pixmap=eog.desktop
image/x-xbitmap=eog.desktop
image/x-xpixmap=eog.desktop
image/vnd.wap.wbmp=eog.desktop
image/g3fax=gimp.desktop
image/x-compressed-xcf=gimp.desktop
image/x-fits=gimp.desktop
image/x-icon=gimp.desktop
image/x-psd=gimp.desktop
image/x-sgi=gimp.desktop
image/x-sun-raster=gimp.desktop
image/x-tga=gimp.desktop
image/x-xcf=gimp.desktop
image/x-xwindowdump=gimp.desktop
application/pdf=evince.desktop
application/x-bzpdf=evince.desktop
application/x-gzpdf=evince.desktop
application/postscript=evince.desktop
application/x-bzpostscript=evince.desktop
application/x-gzpostscript=evince.desktop
image/x-eps=evince.desktop
image/x-bzeps=evince.desktop
image/x-gzeps=evince.desktop
application/x-dvi=evince.desktop
application/x-bzdvi=evince.desktop
application/x-gzdvi=evince.desktop
image/vnd.djvu=evince.desktop
image/tiff=evince.desktop
application/x-cbr=evince.desktop
application/x-cbz=evince.desktop
application/x-cb7=evince.desktop
text/calendar=evolution.desktop
text/x-vcard=evolution.desktop
application/mbox=evolution.desktop
message/rfc822=evolution.desktop
x-scheme-handler/mailto=evolution.desktop
application/x-7z-compressed=org.gnome.FileRoller.desktop
application/x-7z-compressed-tar=org.gnome.FileRoller.desktop
application/x-ace=org.gnome.FileRoller.desktop
application/x-alz=org.gnome.FileRoller.desktop
application/x-ar=org.gnome.FileRoller.desktop
application/x-arj=org.gnome.FileRoller.desktop
application/x-bzip=org.gnome.FileRoller.desktop
application/x-bzip-compressed-tar=org.gnome.FileRoller.desktop
application/x-bzip1=org.gnome.FileRoller.desktop
application/x-bzip1-compressed-tar=org.gnome.FileRoller.desktop
application/x-cabinet=org.gnome.FileRoller.desktop
application/x-cd-image=org.gnome.FileRoller.desktop
application/x-compress=org.gnome.FileRoller.desktop
application/x-compressed-tar=org.gnome.FileRoller.desktop
application/x-cpio=org.gnome.FileRoller.desktop
application/x-deb=org.gnome.FileRoller.desktop
application/x-ear=org.gnome.FileRoller.desktop
application/x-gtar=org.gnome.FileRoller.desktop
application/x-gzip=org.gnome.FileRoller.desktop
application/x-java-archive=org.gnome.FileRoller.desktop
application/x-lha=org.gnome.FileRoller.desktop
application/x-lhz=org.gnome.FileRoller.desktop
application/x-lzip=org.gnome.FileRoller.desktop
application/x-lzip-compressed-tar=org.gnome.FileRoller.desktop
application/x-lzma=org.gnome.FileRoller.desktop
application/x-lzma-compressed-tar=org.gnome.FileRoller.desktop
application/x-lzop=org.gnome.FileRoller.desktop
application/x-lzop-compressed-tar=org.gnome.FileRoller.desktop
application/x-rar=org.gnome.FileRoller.desktop
application/x-rar-compressed=org.gnome.FileRoller.desktop
application/x-rpm=org.gnome.FileRoller.desktop
application/x-rzip=org.gnome.FileRoller.desktop
application/x-tar=org.gnome.FileRoller.desktop
application/x-tarz=org.gnome.FileRoller.desktop
application/x-stuffit=org.gnome.FileRoller.desktop
application/x-war=org.gnome.FileRoller.desktop
application/x-xz=org.gnome.FileRoller.desktop
application/x-xz-compressed-tar=org.gnome.FileRoller.desktop
application/x-zip=org.gnome.FileRoller.desktop
application/x-zip-compressed=org.gnome.FileRoller.desktop
application/x-zoo=org.gnome.FileRoller.desktop
application/zip=org.gnome.FileRoller.desktop
multipart/x-zip=org.gnome.FileRoller.desktop
text/plain=org.gnome.gedit.desktop
text/css=org.gnome.gedit.desktop
text/javascript=org.gnome.gedit.desktop
text/mathml=org.gnome.gedit.desktop
text/x-c++hdr=org.gnome.gedit.desktop
text/x-c++src="org.gnome.gedit.desktop"
text/x-csrc="org.gnome.gedit.desktop"
text/x-chdr=org.gnome.gedit.desktop
text/x-dtd=org.gnome.gedit.desktop
text/x-java=org.gnome.gedit.desktop
text/x-javascript=org.gnome.gedit.desktop
text/x-makefile=org.gnome.gedit.desktop
text/x-moc=org.gnome.gedit.desktop
text/x-pascal=org.gnome.gedit.desktop
text/x-patch=org.gnome.gedit.desktop
text/x-perl=org.gnome.gedit.desktop
text/x-php=org.gnome.gedit.desktop
text/x-python=org.gnome.gedit.desktop
text/x-sql=org.gnome.gedit.desktop
text/x-tcl=org.gnome.gedit.desktop
text/x-tex=org.gnome.gedit.desktop
text/xml=org.gnome.gedit.desktop
application/javascript=org.gnome.gedit.desktop
application/x-cgi=org.gnome.gedit.desktop
application/x-javascript=org.gnome.gedit.desktop
application/x-perl=org.gnome.gedit.desktop
application/x-php=org.gnome.gedit.desktop
application/x-python=org.gnome.gedit.desktop
application/x-shellscript=org.gnome.gedit.desktop
application/xml=org.gnome.gedit.desktop
application/xml-dtd=org.gnome.gedit.desktop
application/x-font-ttf=org.gnome.font-viewer.desktop
application/x-font-pcf=org.gnome.font-viewer.desktop
application/x-font-type1=org.gnome.font-viewer.desktop
application/x-font-otf=org.gnome.font-viewer.desktop
application/x-gnumeric=gnumeric.desktop
application/tab-separated-values=gnumeric.desktop
text/tab-separated-values=gnumeric.desktop
text/csv=gnumeric.desktop
text/x-csv=gnumeric.desktop
application/vnd.lotus-1-2-3=gnumeric.desktop
application/x-123=gnumeric.desktop
application/x-applix-spreadsheet=gnumeric.desktop
application/x-mps=gnumeric.desktop
application/x-oleo=gnumeric.desktop
application/x-planperfect=gnumeric.desktop
application/x-quattropro=gnumeric.desktop
application/x-sc=gnumeric.desktop
application/x-sylk=gnumeric.desktop
application/x-xbase=gnumeric.desktop
text/html=iceweasel.desktop
application/xhtml+xml=iceweasel.desktop
application/rss+xml=iceweasel.desktop
application/rdf+xml=iceweasel.desktop
x-scheme-handler/http=iceweasel.desktop
x-scheme-handler/https=iceweasel.desktop
application/vnd.oasis.opendocument.spreadsheet=libreoffice-calc.desktop
application/vnd.oasis.opendocument.spreadsheet-flat-xml=libreoffice-calc.desktop
application/vnd.oasis.opendocument.spreadsheet-template=libreoffice-calc.desktop
application/vnd.sun.xml.calc=libreoffice-calc.desktop
application/vnd.sun.xml.calc.template=libreoffice-calc.desktop
application/msexcel=libreoffice-calc.desktop
application/vnd.ms-excel=libreoffice-calc.desktop
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet=libreoffice-calc.desktop
application/vnd.ms-excel.sheet.macroenabled.12=libreoffice-calc.desktop
application/vnd.openxmlformats-officedocument.spreadsheetml.template=libreoffice-calc.desktop
application/vnd.ms-excel.template.macroenabled.12=libreoffice-calc.desktop
application/vnd.ms-excel.sheet.binary.macroenabled.12=libreoffice-calc.desktop
application/x-dbf=libreoffice-calc.desktop
text/spreadsheet=libreoffice-calc.desktop
application/vnd.oasis.opendocument.graphics=libreoffice-draw.desktop
application/vnd.oasis.opendocument.graphics-flat-xml=libreoffice-draw.desktop
application/vnd.oasis.opendocument.graphics-template=libreoffice-draw.desktop
application/vnd.sun.xml.draw=libreoffice-draw.desktop
application/vnd.sun.xml.draw.template=libreoffice-draw.desktop
application/vnd.visio=libreoffice-draw.desktop

application/vnd.oasis.opendocument.presentation=libreoffice-impress.desktop
application/vnd.oasis.opendocument.presentation-flat-xml=libreoffice-impress.desktop
application/vnd.oasis.opendocument.presentation-template=libreoffice-impress.desktop
application/vnd.sun.xml.impress=libreoffice-impress.desktop
application/vnd.sun.xml.impress.template=libreoffice-impress.desktop
application/mspowerpoint=libreoffice-impress.desktop
application/vnd.ms-powerpoint=libreoffice-impress.desktop
application/vnd.openxmlformats-officedocument.presentationml.presentation=libreoffice-impress.desktop
application/vnd.ms-powerpoint.presentation.macroenabled.12=libreoffice-impress.desktop
application/vnd.openxmlformats-officedocument.presentationml.template=libreoffice-impress.desktop
application/vnd.ms-powerpoint.template.macroenabled.12=libreoffice-impress.desktop
application/vnd.openxmlformats-officedocument.presentationml.slide=libreoffice-impress.desktop
application/vnd.openxmlformats-officedocument.presentationml.slideshow=libreoffice-impress.desktop
application/vnd.oasis.opendocument.formula=libreoffice-math.desktop
application/vnd.sun.xml.math=libreoffice-math.desktop
application/vnd.oasis.opendocument.text=libreoffice-writer.desktop
application/vnd.oasis.opendocument.text-flat-xml=libreoffice-writer.desktop
application/vnd.oasis.opendocument.text-template=libreoffice-writer.desktop
application/vnd.oasis.opendocument.text-web=libreoffice-writer.desktop
application/vnd.oasis.opendocument.text-master=libreoffice-writer.desktop
application/vnd.sun.xml.writer=libreoffice-writer.desktop
application/vnd.sun.xml.writer.template=libreoffice-writer.desktop
application/vnd.sun.xml.writer.global=libreoffice-writer.desktop
eapplication/vnd.ms-word=libreoffice-writer.desktop
application/x-doc=libreoffice-writer.desktop
application/x-hwp=libreoffice-writer.desktop
application/vnd.wordperfect=libreoffice-writer.desktop
application/wordperfect=libreoffice-writer.desktop
application/vnd.lotus-wordpro=libreoffice-writer.desktop
application/vnd.openxmlformats-officedocument.wordprocessingml.document=libreoffice-writer.desktop
application/vnd.ms-word.document.macroenabled.12=libreoffice-writer.desktop
application/vnd.openxmlformats-officedocument.wordprocessingml.template=libreoffice-writer.desktop
application/vnd.ms-word.template.macroenabled.12=libreoffice-writer.desktop
x-content/software=nautilus-autorun-software.desktop
inode/directory=org.gnome.Nautilus.desktop
application/x-gnome-saved-search=org.gnome.Nautilus.desktop
x-content/audio-player=rhythmbox.desktop
x-content/audio-cdda=sound-juicer.desktop
application/mxf=org.gnome.Totem.desktop
application/ogg=org.gnome.Totem.desktop
application/ram=org.gnome.Totem.desktop
application/sdp=org.gnome.Totem.desktop
application/smil=org.gnome.Totem.desktop
application/smil+xml=org.gnome.Totem.desktop
application/vnd.ms-wpl=org.gnome.Totem.desktop
application/vnd.rn-realmedia=org.gnome.Totem.desktop
application/x-extension-m4a=org.gnome.Totem.desktop
application/x-extension-mp4=org.gnome.Totem.desktop
application/x-flac=org.gnome.Totem.desktop
application/x-flash-video=org.gnome.Totem.desktop
application/x-matroska=org.gnome.Totem.desktop
application/x-netshow-channel=org.gnome.Totem.desktop
application/x-ogg=org.gnome.Totem.desktop
application/x-quicktime-media-link=org.gnome.Totem.desktop
application/x-quicktimeplayer=org.gnome.Totem.desktop
application/x-shorten=org.gnome.Totem.desktop
application/x-smil=org.gnome.Totem.desktop
application/xspf+xml=org.gnome.Totem.desktop
audio/3gpp=org.gnome.Totem.desktop
audio/ac3=org.gnome.Totem.desktop
audio/AMR=org.gnome.Totem.desktop
audio/AMR-WB=org.gnome.Totem.desktop
audio/basic=org.gnome.Totem.desktop
audio/flac=org.gnome.Totem.desktop
audio/midi=org.gnome.Totem.desktop
audio/mp4=org.gnome.Totem.desktop
audio/mpeg=org.gnome.Totem.desktop
audio/mpegurl=org.gnome.Totem.desktop
audio/ogg=org.gnome.Totem.desktop
audio/prs.sid=org.gnome.Totem.desktop
audio/vnd.rn-realaudio=org.gnome.Totem.desktop
audio/x-ape=org.gnome.Totem.desktop
audio/x-flac=org.gnome.Totem.desktop
audio/x-gsm=org.gnome.Totem.desktop
audio/x-it=org.gnome.Totem.desktop
audio/x-m4a=org.gnome.Totem.desktop
audio/x-matroska=org.gnome.Totem.desktop
audio/x-mod=org.gnome.Totem.desktop
audio/x-mp3=org.gnome.Totem.desktop
audio/x-mpeg=org.gnome.Totem.desktop
audio/x-mpegurl=org.gnome.Totem.desktop
audio/x-ms-asf=org.gnome.Totem.desktop
audio/x-ms-asx=org.gnome.Totem.desktop
audio/x-ms-wax=org.gnome.Totem.desktop
audio/x-ms-wma=org.gnome.Totem.desktop
audio/x-musepack=org.gnome.Totem.desktop
audio/x-pn-aiff=org.gnome.Totem.desktop
audio/x-pn-au=org.gnome.Totem.desktop
audio/x-pn-realaudio=org.gnome.Totem.desktop
audio/x-pn-realaudio-plugin=org.gnome.Totem.desktop
audio/x-pn-wav=org.gnome.Totem.desktop
audio/x-pn-windows-acm=org.gnome.Totem.desktop
audio/x-realaudio=org.gnome.Totem.desktop
audio/x-real-audio=org.gnome.Totem.desktop
audio/x-sbc=org.gnome.Totem.desktop
audio/x-scpls=org.gnome.Totem.desktop
audio/x-speex=org.gnome.Totem.desktop
audio/x-tta=org.gnome.Totem.desktop
audio/x-vorbis=org.gnome.Totem.desktop
audio/x-vorbis+ogg=org.gnome.Totem.desktop
audio/x-wav=org.gnome.Totem.desktop
audio/x-wavpack=org.gnome.Totem.desktop
audio/x-xm=org.gnome.Totem.desktop
image/vnd.rn-realpix=org.gnome.Totem.desktop
image/x-pict=org.gnome.Totem.desktop
misc/ultravox=org.gnome.Totem.desktop
text/google-video-pointer=org.gnome.Totem.desktop
text/x-google-video-pointer=org.gnome.Totem.desktop
video/3gpp=org.gnome.Totem.desktop
video/dv=org.gnome.Totem.desktop
video/fli=org.gnome.Totem.desktop
video/flv=org.gnome.Totem.desktop
video/mp2t=org.gnome.Totem.desktop
video/mp4=org.gnome.Totem.desktop
video/mp4v-es=org.gnome.Totem.desktop
video/mpeg=org.gnome.Totem.desktop
video/msvideo=org.gnome.Totem.desktop
video/ogg=org.gnome.Totem.desktop
video/quicktime=org.gnome.Totem.desktop
video/vivo=org.gnome.Totem.desktop
video/vnd.divx=org.gnome.Totem.desktop
video/vnd.rn-realvideo=org.gnome.Totem.desktop
video/vnd.vivo=org.gnome.Totem.desktop
video/webm=org.gnome.Totem.desktop
video/x-anim=org.gnome.Totem.desktop
video/x-avi=org.gnome.Totem.desktop
video/x-flc=org.gnome.Totem.desktop
video/x-fli=org.gnome.Totem.desktop
video/x-flic=org.gnome.Totem.desktop
video/x-flv=org.gnome.Totem.desktop
video/x-m4v=org.gnome.Totem.desktop
video/x-matroska=org.gnome.Totem.desktop
video/x-mpeg=org.gnome.Totem.desktop
video/x-ms-asf=org.gnome.Totem.desktop
video/x-ms-asx=org.gnome.Totem.desktop
video/x-msvideo=org.gnome.Totem.desktop
video/x-ms-wm=org.gnome.Totem.desktop
video/x-ms-wmv=org.gnome.Totem.desktop
video/x-ms-wmx=org.gnome.Totem.desktop
video/x-ms-wvx=org.gnome.Totem.desktop
video/x-nsv=org.gnome.Totem.desktop
video/x-ogm+ogg=org.gnome.Totem.desktop
video/x-theora+ogg=org.gnome.Totem.desktop
video/x-totem-stream=org.gnome.Totem.desktop
x-content/video-dvd=org.gnome.Totem.desktop
x-content/video-vcd=org.gnome.Totem.desktop
x-content/video-svcd=org.gnome.Totem.desktop
x-scheme-handler/pnm=org.gnome.Totem.desktop
x-scheme-handler/mms=org.gnome.Totem.desktop
x-scheme-handler/net=org.gnome.Totem.desktop
x-scheme-handler/rtp=org.gnome.Totem.desktop
x-scheme-handler/rtsp=org.gnome.Totem.desktop
x-scheme-handler/mmsh=org.gnome.Totem.desktop
x-scheme-handler/uvox=org.gnome.Totem.desktop
x-scheme-handler/icy=org.gnome.Totem.desktop
x-scheme-handler/icyx=org.gnome.Totem.desktop
x-scheme-handler/ghelp=yelp.desktop
x-scheme-handler/help=yelp.desktop
x-scheme-handler/info=yelp.desktop
x-scheme-handler/man=yelp.desktop

Burada gnome ait örnek bir default.list içeriği var. Siz en azından sık kullandığınız uygulama uzantılarına göre ihtiyacınız olanları düzenleyebilirsiniz. Bu listeyi size, uzantılar hakkında fikir vermek için paylaşıyorum. Birebir aynısını kullanamazsınız. Burada = işaretinden sonra ki bölüme kendi kullanmak istediğiniz programı yazacaksınız.
  Tavsiyem bu tür düzenlemeleri harici bir bellek veya bulut servisler üzerine depolamanız. Böylelikle tekrar kurulum yaptığınızda yeniden düzenleme derdiniz olmaz.

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