Because I don't understand Ruby, but want to use the ruby based program mdl (markdownlint), I have installed it using snap.

While I can run the program, if I try and set up a customizations in a ~/.mdlrc file. I get the following error

 $ mdl README.md
 `read': Permission denied @ rb_sysopen - /home/mikeg/.mdlrc
         from /snap/mdl/171/lib/ruby/gems/2.4.0/gems/mixlib-config-3.0.6/lib/mixlib/config.rb:63:in
         from /snap/mdl/171/lib/ruby/gems/2.4.0/gems/mdl-0.10.0/lib/mdl/cli.rb:122:in
         from /snap/mdl/171/lib/ruby/gems/2.4.0/gems/mdl-0.10.0/lib/mdl.rb:16:in
         from /snap/mdl/171/lib/ruby/gems/2.4.0/gems/mdl-0.10.0/bin/mdl:10:in `<top
         from /snap/mdl/171/bin/mdl:23:in `load'
         from /snap/mdl/171/bin/mdl:23:in `<main>'

I don't understand where the permission issue comes from since

 $ ls -l ~/.mdlrc ~/.mdlrc.style.rb
 -rw-rw-r-- 1 mikeg mikeg 171 Aug 14 16:06 /home/mikeg/.mdlrc
 -rw-rw-r-- 1 mikeg mikeg   4 Aug 14 16:06 /home/mikeg/.mdlrc.style.rb


drwxr-xr-x 303 mikeg mikeg 65536 Aug 14 21:53 /home/mikeg

As a result, I can't figure out how to fix this. Can anyone help me.

Note that I'm running Mate 18.06. SELinux is not installed, but AppArmor is active and going through my /var/log/syslog* files I get

syslog.7.gz:Aug 17 09:08:40 XXXX kernel: [978608.742842] audit: type=1400 audit(1597669720.954:2800): apparmor="DENIED" operation="open" profile="snap.mdl.mdl" name="/home/mi/.mdlrc" pid=13189 comm="ruby" requested_mask="r" denied_mask="r" fsuid=1000 ouid=1000



  • Add the permissions of the parent directory to your question. – Nasir Riley Aug 15 '20 at 14:19
  • done. It's a personal machine. – mikemtnbikes Aug 15 '20 at 15:11
  • My mistake, I meant your home directory. Does /home/mikeg have 700 permissions? Add that to your question. – Nasir Riley Aug 15 '20 at 15:14
  • Is SELinux enabled? – Nasir Riley Aug 15 '20 at 15:57
  • Nope. Not even installed. ` $ getenforce Command 'getenforce' not found, but can be installed with: sudo apt install selinux-utils` – mikemtnbikes Aug 16 '20 at 13:27

@NasirRiely's question about SELinux was helpful in identifying the root cause of the issue which is a combination of apparmor permissions and snap. Apparently it can't read files in my home dir and installing the mdl snap --classic option didn't help (it was ignored for security reasons).

I started going down that rabbit hole, but decided to stop and simply install ruby and mdl using gems. That is,

$ sudo apt-get install ruby-full
$ gem install mdl

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