BUT don’t edit it just yet. What is the contents of that file?
If you do need to change it do
sudo systemctl edit mariadb
and add the line… You need to include the right section - [service] I expect.
ProtectHome=false
[edit]
Actually my service file is as below before any update and ProtectHome =true
Compare this to yours.
pi@emonpi:~ $ cat /lib/systemd/system/mariadb.service
#
# /etc/systemd/system/mariadb.service
#
# This file is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
#
# Thanks to:
# Daniel Black
# Erkan Yanar
# David Strauss
# and probably others
[Unit]
Description=MariaDB 10.3.17 database server
Documentation=man:mysqld(8)
Documentation=https://mariadb.com/kb/en/library/systemd/
After=network.target
[Install]
WantedBy=multi-user.target
Alias=mysql.service
Alias=mysqld.service
[Service]
##############################################################################
## Core requirements
##
Type=notify
# Setting this to true can break replication and the Type=notify settings
# See also bind-address mysqld option.
PrivateNetwork=false
##############################################################################
## Package maintainers
##
User=mysql
Group=mysql
# To allow memlock to be used as non-root user if set in configuration
CapabilityBoundingSet=CAP_IPC_LOCK
# Prevent writes to /usr, /boot, and /etc
ProtectSystem=full
# Doesn't yet work properly with SELinux enabled
# NoNewPrivileges=true
PrivateDevices=true
# Prevent accessing /home, /root and /run/user
ProtectHome=true
# Execute pre and post scripts as root, otherwise it does it as User=
PermissionsStartOnly=true
ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld
# Perform automatic wsrep recovery. When server is started without wsrep,
# galera_recovery simply returns an empty string. In any case, however,
# the script is not expected to return with a non-zero status.
# It is always safe to unset _WSREP_START_POSITION environment variable.
# Do not panic if galera_recovery script is not available. (MDEV-10538)
ExecStartPre=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION"
ExecStartPre=/bin/sh -c "[ ! -e /usr/bin/galera_recovery ] && VAR= || \
VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ] \
&& systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1"
# Needed to create system tables etc.
# ExecStartPre=/usr/bin/mysql_install_db -u mysql
# Start main service
# MYSQLD_OPTS here is for users to set in /etc/systemd/system/mariadb.service.d/MY_SPECIAL.conf
# Use the [Service] section and Environment="MYSQLD_OPTS=...".
# This isn't a replacement for my.cnf.
# _WSREP_NEW_CLUSTER is for the exclusive use of the script galera_new_cluster
ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION
ExecStartPost=/etc/mysql/debian-start
# Unset _WSREP_START_POSITION environment variable.
ExecStartPost=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION"
KillSignal=SIGTERM
# Don't want to see an automated SIGKILL ever
SendSIGKILL=no
# Restart crashed server only, on-failure would also restart, for example, when
# my.cnf contains unknown option
Restart=on-abort
RestartSec=5s
UMask=007
##############################################################################
## USERs can override
##
##
## by creating a file in /etc/systemd/system/mariadb.service.d/MY_SPECIAL.conf
## and adding/setting the following under [Service] will override this file's
## settings.
# Useful options not previously available in [mysqld_safe]
# Kernels like killing mysqld when out of memory because its big.
# Lets temper that preference a little.
# OOMScoreAdjust=-600
# Explicitly start with high IO priority
# BlockIOWeight=1000
# If you don't use the /tmp directory for SELECT ... OUTFILE and
# LOAD DATA INFILE you can enable PrivateTmp=true for a little more security.
PrivateTmp=false
##
## Options previously available to be set via [mysqld_safe]
## that now needs to be set by systemd config files as mysqld_safe
## isn't executed.
##
# Number of files limit. previously [mysqld_safe] open-file-limit
LimitNOFILE=16364
# Maximium core size. previously [mysqld_safe] core-file-size
# LimitCore=
# Nice priority. previously [mysqld_safe] nice
# Nice=-5
# Timezone. previously [mysqld_safe] timezone
# Environment="TZ=UTC"
# Library substitutions. previously [mysqld_safe] malloc-lib with explicit paths
# (in LD_LIBRARY_PATH) and library name (in LD_PRELOAD).
# Environment="LD_LIBRARY_PATH=/path1 /path2" "LD_PRELOAD=
# Flush caches. previously [mysqld_safe] flush-caches=1
# ExecStartPre=sync
# ExecStartPre=sysctl -q -w vm.drop_caches=3
# numa-interleave=1 equalivant
# Change ExecStart=numactl --interleave=all /usr/sbin/mysqld......
# crash-script equalivent
# FailureAction=
Hi @borpin, thanks Brian. I’m on low-write 9.8.8 and yes my SQL DB is in /home/pi/data/mysql I gather the problem is something to do with that but I don’t understand what. I’m confused about what is wrong and what I need to do about it.
I tried creating /etc/systemd/system/mariadb.service.d/override.conf with the contents:
[service]
ProtectHome=false
but it doesn’t seem to make any difference when I restart the DB:
Jun 13 13:55:51 emonpi mysqld[8396]: 2020-06-13 13:55:51 1995755312 [Warning] Can't create test file /home/pi/data/mysql/emonpi.lower-test
Firstly it is a bad idea to create the file manually especially in the /etc/systemd/ folder. Note the source file is in lib. Hence the suggestion of mine to use sudo systemctl edit.
When you restarted the service did you get a warning?
You are basically starting the service as it was before, it doesn’t yet know to include the override. If you do a systemctl status mariadb.service it will tell you if you are using the override file.
Try that command then
sudo systemctl daemon-reload
Then the status again. I expect it will list the override file then (and it may start!).
Probably the default service file was changed on update - we have seen it before.
I strongly suggest you consider updating to Buster from Stretch - it does ideally mean a new card, but the USB import makes it relatively painless. Also there are lots of underlying fixes (such as moving data out of home) introduced since 9.x.
At some point, something will break that cannot be fixed.
Well, stretch is just about to start its two years of LTS so I think upgrading to buster on a system I’d like to stay as stable as possible is premature. What worked should keep working. I trust Debian / Raspberry Pi OS to produce sensible updates within the release, and applications built on it should continue to run. As regards emoncms, I don’t believe my changes to the flot library have been pulled into upstream yet (ever?) so I will have to reapply those whenever I do upgrade, and I have logging sorted to my satisfaction, so I’m pretty happy with what I have.
