It seems that on a Ubuntu 14.04 machine the user mysql cannot access anything. It is not writing logs nor reading files. Witness:

 - bruno():mysql$ cat /etc/passwd | grep mysql
mysql:x:116:127:MySQL Server,,,:/nonexistent:/bin/false

 - bruno():mysql$ sudo mysql_install_db
Installing MySQL system tables...
140818 18:16:50 [ERROR] Can't read from messagefile '/usr/share/mysql/english/errmsg.sys'
140818 18:16:50 [ERROR] Aborting
140818 18:16:50 [Note] 

Installation of system tables failed!  Examine the logs in
/var/lib/mysql for more information.

...boilerplate trimmed...

 - bruno():mysql$ ls -la /usr/share/mysql/english/errmsg.sys
-rw-r--r-- 1 root root 59535 Jul 29 13:40 /usr/share/mysql/english/errmsg.sys
 - bruno():mysql$ wc -l /usr/share/mysql/english/errmsg.sys
16 /usr/share/mysql/english/errmsg.sys

Here we have seen that mysql cannot read /usr/share/mysql/english/errmsg.sys even though the permissions are open to read it, and in fact the regular login user can read the file (with wc). Additionally, MySQL is not writing any logs:

 - bruno():mysql$ ls -la /var/log/mysql
total 8
drwxr-s---  2 mysql adm    4096 Aug 18 16:10 .
drwxrwxr-x 18 root  syslog 4096 Aug 18 16:10 ..

What might cause this user to not be able to access anything? What can I do about it?