[debian-mysql] Bug#742900: systemd service file for mysqld

[Christian McHugh]

I've got mysql running with a systemd service file on my machine. As was
suggested earlier in the bug report, I started with the fedora scripts so
there may be some fedoraisms to check on. The only problem I had just using
them was an issue with mysql-wait-ready where the ping line was improperly
formated resulting in usage info getting printed out. As you can see, I
added a little bit of extra output around that section to help debug.
Since /usr/bin/mysqld_safe sources /etc/mysql/debian.cnf and systemd runs
everything as the mysql user, I also had to chgrp mysql
/etc/mysql/debian.cnf; chmod g+r /etc/mysql/debian.cnf.



####################### mysql.service
# For more info about custom unit files, see systemd.unit(5) or
#
http://fedoraproject.org/wiki/Systemd#How_do_I_customize_a_unit_file.2F_add_a_custom_unit_file.3F

# For example, if you want to increase mysql's open-files-limit to 10000,
# you need to increase systemd's LimitNOFILE setting, so create a file named
# "/etc/systemd/system/mariadb.service.d/limits.conf" containing:
#       [Service]
#       LimitNOFILE=10000

[Unit]
Description=MySQL database server
After=syslog.target network.target

[Service]
Type=simple
User=mysql
Group=mysql

ExecStartPre=/usr/bin/mysql-prepare-db-dir %n
# Note: we set --basedir to prevent probes that might trigger SELinux
alarms,
# per bug #547485
ExecStart=/usr/bin/mysqld_safe --basedir=/usr
ExecStartPost=/usr/bin/mysql-wait-ready $MAINPID

# Give a reasonable amount of time for the server to start up/shut down
TimeoutSec=300

# Security
PrivateTmp=yes
#InaccessibleDirectories=/boot /.config /home/backups /home/bill
/home/sleeper /lib32 /media /mnt /opt /proc /root /srv /sys
#ReadOnlyDirectories=/bin /etc /sbin /usr
#CapabilityBoundingSet=~CAP_SYS_PTRACE
#DeviceAllow=/dev/null rw
#NoNewPrivileges=yes

[Install]
WantedBy=multi-user.target



####################### /usr/bin/mysql-prepare-db-dir
#!/bin/sh

# This script creates the mysql data directory during first service start.
# In subsequent starts, it does nothing much.

# extract value of a MySQL option from config files
# Usage: get_mysql_option SECTION VARNAME DEFAULT
# result is returned in $result
# We use my_print_defaults which prints all options from multiple files,
# with the more specific ones later; hence take the last match.
get_mysql_option(){
        result=`/usr/bin/my_print_defaults "$1" | sed -n "s/^--$2=//p" |
        tail -n 1`
        if [ -z "$result" ]; then
            # not found, use default
            result="$3"
        fi
}

# Defaults here had better match what mysqld_safe will default to
get_mysql_option mysqld datadir "/var/lib/mysql"
datadir="$result"
get_mysql_option mysqld_safe log-error "/var/log/mysql/error.log"
errlogfile="$result"
get_mysql_option mysqld socket "$datadir/mysql.sock"
socketfile="$result"

# Absorb configuration settings from the specified systemd service file,
# or the default "mysqld" service if not specified
SERVICE_NAME="$1"
if [ x"$SERVICE_NAME" = x ]
then
    SERVICE_NAME=mysqld.service
fi

myuser=`systemctl show -p User "${SERVICE_NAME}" |
  sed 's/^User=//'`
if [ x"$myuser" = x ]
then
    myuser=mysql
fi

mygroup=`systemctl show -p Group "${SERVICE_NAME}" |
  sed 's/^Group=//'`
if [ x"$mygroup" = x ]
then
    mygroup=mysql
fi

# Set up the errlogfile with appropriate permissions
touch "$errlogfile"
chown "$myuser:$mygroup" "$errlogfile"
chmod 0640 "$errlogfile"
#[ -x /sbin/restorecon ] && /sbin/restorecon "$errlogfile"

# We check if there is already a process using the socket file,
# since otherwise this systemd service file could report false
# positive result when starting and mysqld_safe could remove
# a socket file, which actually uses a different daemon.
if fuser "$socketfile" > /dev/null ; then
    echo "Socket file $socketfile exists." >&2
    echo "Is another MySQL daemon already running with the same unix
    socket?" >&2
    exit 1
fi

# Make the data directory
if [ ! -d "$datadir/mysql" ] ; then
    # First, make sure $datadir is there with correct permissions
    # (note: if it's not, and we're not root, this'll fail ...)
    if [ ! -e "$datadir" -a ! -h "$datadir" ]
    then
        mkdir -p "$datadir" || exit 1
    fi
    chown "$myuser:$mygroup" "$datadir"
    chmod 0755 "$datadir"
#    [ -x /sbin/restorecon ] && /sbin/restorecon "$datadir"

    # Now create the database
    echo "Initializing MySQL database"
    /usr/bin/mysql_install_db --datadir="$datadir" --user="$myuser"
    ret=$?
    if [ $ret -ne 0 ] ; then
        echo "Initialization of MySQL database failed." >&2
        echo "Perhaps /etc/my.cnf is misconfigured." >&2
        # Clean up any partially-created database files
        if [ ! -e "$datadir/mysql/user.frm" ] ; then
            rm -rf "$datadir"/*
        fi
        exit $ret
    fi
    # In case we're running as root, make sure files are owned properly
    chown -R "$myuser:$mygroup" "$datadir"
fi

exit 0



####################### /usr/bin/mysql-wait-ready
#!/bin/sh

# This script waits for mysqld to be ready to accept connections
# (which can be many seconds or even minutes after launch, if there's
# a lot of crash-recovery work to do).
# Running this as ExecStartPost is useful so that services declared as
# "After mysqld" won't be started until the database is really ready.

# Service file passes us the daemon's PID (actually, mysqld_safe's PID)
daemon_pid="$1"

# extract value of a MySQL option from config files
# Usage: get_mysql_option SECTION VARNAME DEFAULT
# result is returned in $result
# We use my_print_defaults which prints all options from multiple files,
# with the more specific ones later; hence take the last match.
get_mysql_option(){
result=`/usr/bin/my_print_defaults "$1" | sed -n "s/^--$2=//p" |
tail -n 1`
if [ -z "$result" ]; then
    # not found, use default
    result="$3"
fi
}

# Defaults here had better match what mysqld_safe will default to
get_mysql_option mysqld datadir "/var/lib/mysql"
datadir="$result"
get_mysql_option mysqld socket "/var/lib/mysql/mysql.sock"
socketfile="$result"

# Wait for the server to come up or for the mysqld process to disappear
ret=0
while /bin/true; do
MYSQLDRUNNING=0
if [ -d "/proc/${daemon_pid}" ] ; then
    MYSQLDRUNNING=1
fi
RESPONSE=`/usr/bin/mysqladmin --no-defaults --socket="$socketfile"
--user=UNKNOWN_MYSQL_USER ping 2>&1`
mret=$?
if [ $mret -eq 0 ] && [ $MYSQLDRUNNING -eq 1 ]; then
    break
fi
# exit codes 1, 11 (EXIT_CANNOT_CONNECT_TO_SERVICE) are expected,
# anything else suggests a configuration error
if [ $mret -ne 1 -a $mret -ne 11 ]; then
            echo "Received bad response from mysql..."
            echo "$RESPONSE"
            echo "$mret"
    ret=1
    break
fi
# "Access denied" also means the server is alive
echo "$RESPONSE" | grep -q "Access denied for user" && break

# Check process still exists
if ! /bin/kill -0 $daemon_pid 2>/dev/null; then
            echo "Process does not exist"
    ret=1
    break
fi
sleep 1
done

exit $ret
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