Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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5.5.54
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None
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RHEL6 / CentOS6 - tested with centos/6 VM base image for Vagrant which is CentOS 6.8 at this point
Description
service mysql start bails out with weird error message from the new mysqld_safe_helper binary when having log-error option set in either [mysqld] or [mysqld_safe] section of my.cnf. Whether log-error is used with an explicit file name argument or not doesn't matter. Also when not having log-error in the config file at all mysqld_safe_helper is still throwing an error, but in this case the service startup script reports SUCCESS instead of ERROR
The error message is
# service mysql start
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Starting MySQL.161228 12:32:33 mysqld_safe Logging to '/var/lib/mysql/localhost.localdomain.err'.
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161228 12:32:33 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
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/usr/bin/mysqld_safe_helper: Can't create/write to file '' (Errcode: -597589344)
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(Jira does not show this, but the actual file name shown in the error message is the unicode placeholder character for code point U+0001, and not just an empty string)
The actual error code varies and is usually a large positive or negative value, but not a valid error code.
When looking at strace output the parameters passed to mysqld_safe_helper look fine:
execve("/usr/bin/mysqld_safe_helper", ["/usr/bin/mysqld_safe_helper", "mysql", "log", "/var/lib/mysql/localhost.localdomain.err"], ["TERM=xterm", "PATH=/sbin:/usr/sbin:/bin:/usr/bin:/usr/bin", "PWD=/usr", "SHLVL=2", "MYSQL_HOME=/usr", "_=/usr/bin/mysqld_safe_helper"]) = 0
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Also when running mysqld_safe_helper with the same arguments manually it works as expected without throwing an error at all:
/usr/bin/mysqld_safe_helper mysql log /var/lib/mysql/localhost.localdomain.err
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Also when passing in an invalid file name a correct error message is displayed (^A here was entered using CTRL-V CTRL-A, so it is really 0x01
/usr/bin/mysqld_safe_helper mysql log ^A
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/usr/bin/mysqld_safe_helper: Can't create/write to file '' (Errcode: 13)
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(again the file name in the actual error message is the U+0001 unicode placeholder, and not just an empty string)
Attachments
Issue Links
- relates to
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- Closed
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Activity
How to reproduce:
- set up VM
vagrant init centos/6vagrant upvagrant ssh
- in VM shell
sudo bashcat > /etc/yum.repos.d/mariadb.repo <<EOF[mariadb]name = MariaDBbaseurl = http://yum.mariadb.org/5.5/centos6-amd64gpgkey=https://yum.mariadb.org/RPM-GPG-KEY-MariaDBgpgcheck=1EOFyum install MariaDB-serverservice mysql start
Turns out the actual problem is SELINUX=enforcing mode preventing changing the effective user ID for this new binary unknown to it.
from failing invocations strace:
4888 execve("/usr/bin/mysqld_safe_helper", ["/usr/bin/mysqld_safe_helper", "mysql", "log", "/var/lib/mysql/localhost.localdo"...], [/* 6 vars */] <unfinished ...>
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[...]
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4888 setgroups(1, [499]) = -1 EPERM (Operation not permitted)
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4888 setgid(499) = -1 EPERM (Operation not permitted)
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4888 write(2, "/usr/bin/mysqld_safe_helper", 27) = 27
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4888 write(2, ": ", 2) = 2
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4888 write(2, "Can't create/write to file '\1' ("..., 51) = 51
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4888 write(2, "\n", 1) = 1
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4888 clock_gettime(CLOCK_REALTIME, {1483100529, 629773869}) = 0
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4888 exit_group(1)
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So the failure is understandable now ... not the source of the misleading error message though as it seems to stem from my_set_user() and not related to file system access at all ...
Service startup now also fails after removing log-error from the configuration file again, so this is not a reliable workaround either ...