Sonny's questions

I am migrating a web application that was previously running on Ubuntu 12.04 LTS. It makes extensive use of /dev/shm/. I'm finding that the application data is disappearing from /dev/shm/ on the Ubuntu 16.04 LTS server.

Is there some sort of garbage collection that's deleting the files and directories from there? I see that 12.04 is configured with this symbolic link: /dev/shm -> /run/shm, whereas 16.04 has exactly the opposite: /run/shm -> /dev/shm. I don't see how that would make any difference, though.

UPDATES

• I suspected AppArmor, but removing it did not change the behavior
• The removal of the directory structures seems to happen every five minutes
• Directories with files in them eventually get deleted, but not as quickly
• I'm suspecting the age of the files/directories affects deletion
• It looks like this guy is experiencing the same issue.

Background

/etc/mysql/my.cnf is a symbolic link to /etc/alternatives/my.cnf

/etc/alternatives/my.cnf is mostly comments, but has this at the bottom:

!includedir /etc/mysql/conf.d/
!includedir /etc/mysql/mysql.conf.d/

/etc/mysql/conf.d/ has the files: mysql.cnf and mysqldump.cnf
/etc/mysql/mysql.conf.d/ has the files: mysqld.cnf and mysqld_safe_syslog.cnf

I've found that /etc/mysql/mysql.conf.d/mysqld.cnf holds the configurations that I previously would in /etc/mysql/my.cnf.

Observations and Questions

It appears to me that these changes are an attempt to modularize the MySQL configuration. In order to maintain that modularization, it seems that the best practice would be to add an new file, overrides.cnf, to the /etc/mysql/mysql.conf.d/ directory, which contains only the configuration options that I want to add and change.

Am I on the correct path here?

I want to mitigate CVE-2016-3115. The report from OpenSSH states that the vulnerability exists when X11Forwarding is enabled. It shows as enabled in my /etc/ssh/sshd_config, but I don't know why. It's a server that I only access via SSH (PuTTY) and SFTP. What are the possible issues that could come from disabling X11Forwarding?

PCI compliance will fail when the CVE-2015-5352 vulnerability is present. OpenSSH 6.9 fixes this vulnerability, but none of the supported versions of Ubuntu (12.04, 14.04, 15.04 and 15.10) have been patched.

What is the best way to address this vulnerability?

I would like a tail -f type of behavior that reads the entire file and then continues to follow it as it's written to.

SOLUTION

Based on the answer I accepted, this works: tail -f -n +1 {filename}

Why it works: The -f option continues to "follow" the file and output new lines as they are written to the file. The -n +1 instructs tail to start reading the file from the first line. Using -n -10 would start with the last ten lines of the file.