1 | <?xml version="1.0" encoding="ISO-8859-1"?>
|
---|
2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
---|
3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
|
---|
4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
|
---|
5 | %general-entities;
|
---|
6 | ]>
|
---|
7 |
|
---|
8 | <sect1 id="upgradedb" xreflabel="Upgrade Database">
|
---|
9 | <?dbhtml filename="upgradedb.html"?>
|
---|
10 |
|
---|
11 | <sect1info>
|
---|
12 | <date>$Date$</date>
|
---|
13 | </sect1info>
|
---|
14 |
|
---|
15 | <title>Important notes about upgrading Database Server Software</title>
|
---|
16 |
|
---|
17 | <para>Lets start this chapter a bit dramatic with a screenshot
|
---|
18 | of an issue that really happened. Don't be scared if you read
|
---|
19 | this the first time, this issue will not occur if you are going
|
---|
20 | to install the software the first time:</para>
|
---|
21 |
|
---|
22 | <screen>$ sudo systemctl status postgresql
|
---|
23 | -- postgresql.service - PostgreSQL database server
|
---|
24 | Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; vendor preset: enabled)
|
---|
25 | Active: failed (Result: exit-code) since Tue 2021-10-26 17:11:53 CDT; 2min 49s ago
|
---|
26 | Process: 17336 ExecStart=/usr/bin/pg_ctl -s -D ${PGROOT}/data start -w -t 120 (code=exited, status=1/FAILURE)
|
---|
27 | CPU: 7ms
|
---|
28 |
|
---|
29 | Oct 26 17:11:53 SVRNAME systemd[1]: Starting PostgreSQL database server...
|
---|
30 | Oct 26 17:11:53 SRVNAME postgres[17338]: 2021-10-26 17:11:53.420 CDT [17338] FATAL: database files are incompatible with server
|
---|
31 | Oct 26 17:11:53 SRVNAME postgres[17338]: 2021-10-26 17:11:53.420 CDT [17338] DETAIL: The data directory was initialized by PostgreSQL version 13, which is not compatible with this version 14.0.
|
---|
32 | Oct 26 17:11:53 SRVNAME postgres[17336]: pg_ctl: could not start server
|
---|
33 | Oct 26 17:11:53 SRVNAME postgres[17336]: Examine the log output.
|
---|
34 | Oct 26 17:11:53 SRVNAME systemd[1]: postgresql.service: Control process exited, code=exited, status=1/FAILURE
|
---|
35 | Oct 26 17:11:53 SRVNAME systemd[1]: postgresql.service: Failed with result 'exit-code'.
|
---|
36 | Oct 26 17:11:53 SRVNAME systemd[1]: Failed to start PostgreSQL database server.</screen>
|
---|
37 |
|
---|
38 | <para>
|
---|
39 | If you like to avoid those situations like the one above finding
|
---|
40 | your database server software refusing to start, it is highly
|
---|
41 | recommended to read the following thoughts about how to upgrade
|
---|
42 | a DBMS (Database Management System) prior to actually doing the
|
---|
43 | upgrade.
|
---|
44 | </para>
|
---|
45 | <para>
|
---|
46 | The root cause of the issue shown above was an upgrade
|
---|
47 | of the server software to a newer major version but letting the
|
---|
48 | data files untouched. The admin was able to recover without any
|
---|
49 | loss of data.
|
---|
50 | </para>
|
---|
51 | <para>
|
---|
52 | Even if you are installing a DBMS the initial time, read this
|
---|
53 | section too, it might give you a guideline on how to set up backup
|
---|
54 | and restore procedures (at least the strategy for building
|
---|
55 | them) which are sufficient for your needs and for the safety
|
---|
56 | of your data.
|
---|
57 | </para>
|
---|
58 |
|
---|
59 | <sect2>
|
---|
60 | <title>Upgrade database server packages</title>
|
---|
61 |
|
---|
62 | <para>
|
---|
63 | Usually, DB systems work on a bunch of files which holds
|
---|
64 | the database metadata and the data itself. Those files
|
---|
65 | are highly optimized in their internal structures for use
|
---|
66 | by the server software. When upgrading such a server software,
|
---|
67 | it can happen that the server software expects a slightly
|
---|
68 | different file format than it has been created by previous
|
---|
69 | versions. In the best case, the new software can act on the
|
---|
70 | old format as well - while not benefitting from newer formats
|
---|
71 | which might result in better performance or of other improvements.
|
---|
72 | It can also happen that the new server software will reformat
|
---|
73 | the data files automatically at the first start.
|
---|
74 | </para>
|
---|
75 |
|
---|
76 | <para>
|
---|
77 | Unfortunatly, the most likly case is that the new server
|
---|
78 | software complains about invalid data file formats and exits.
|
---|
79 | When this happens and you have overwritten the installed server
|
---|
80 | software with the new one, you are kind of lost as you lsot the
|
---|
81 | software which can read the data files and the new software is
|
---|
82 | unwilling to do so.
|
---|
83 | </para>
|
---|
84 |
|
---|
85 | <para>
|
---|
86 | Changes in data file formats come usually beside major
|
---|
87 | version changes. But there is no guaranty. Before upgrading
|
---|
88 | the server software, check the documentation if there are
|
---|
89 | changes which will require a data file reformat.
|
---|
90 | </para>
|
---|
91 |
|
---|
92 | <para>
|
---|
93 | Of course, if you have databases with content which is not
|
---|
94 | easily to rebuild, it is always a good idea of creating backups
|
---|
95 | of the database from time to time. When going to upgrade the
|
---|
96 | server software, the time is quite good to run another backup.
|
---|
97 | </para>
|
---|
98 |
|
---|
99 | <sect3>
|
---|
100 | <title>Upgrade by backup and restore</title>
|
---|
101 |
|
---|
102 | <note>
|
---|
103 | <para>
|
---|
104 | A backup is meaningless if there is no verified process
|
---|
105 | to restore the data from this backup. When running a
|
---|
106 | database server, you should not only create backups but you
|
---|
107 | should also verify that the process you designed to fullfill
|
---|
108 | the restore task is working properly. When you encounter a
|
---|
109 | problem with the restore at the time you urgently have to
|
---|
110 | rely on the backup data, it is too late - your database are
|
---|
111 | in high danger at this moment.
|
---|
112 | </para>
|
---|
113 | </note>
|
---|
114 |
|
---|
115 | <para>
|
---|
116 | In general, most (all?) database server software provides
|
---|
117 | some basic tools to create backups of your data. Usually,
|
---|
118 | the backups created with those tools can be read by newer
|
---|
119 | versions of the software (here the restore tool). The other
|
---|
120 | way round (older resote tools can work with newer backup data)
|
---|
121 | is not defined and you should <emphasis>never</emphasis>
|
---|
122 | blindly assume that it would work. It might do, but usually
|
---|
123 | it doesn't.
|
---|
124 | </para>
|
---|
125 |
|
---|
126 | <para>
|
---|
127 | The most easiest way to upgrade your database files is to
|
---|
128 | </para>
|
---|
129 |
|
---|
130 | <itemizedlist>
|
---|
131 | <listitem>
|
---|
132 | <para>Create a full database backup using the old tools.</para>
|
---|
133 | <para>This step creates an offline copy of the database
|
---|
134 | files ready to be used for long term archiving, for desaster
|
---|
135 | recovery or just as a preparation for upgrade. This offline
|
---|
136 | backups consists of the full one-to-one copy of the current
|
---|
137 | database files or a backup of the files from a certain time
|
---|
138 | in history plus all journal data (that is Oracle(R)
|
---|
139 | terminology, its called "Continuous Archiving" or "write
|
---|
140 | ahead log (WAL)" in Postgresql) containing information about
|
---|
141 | changes made to the data content. The later are more quickly
|
---|
142 | to create if the DB software provides such kind of journal as
|
---|
143 | you only have to save the changes which are recorded in those
|
---|
144 | journals from the last backup upto now. The amount of data to
|
---|
145 | backup is much less than doing a full backup all the time.</para>
|
---|
146 | <para>In terms of upgrading a DB server software, it is
|
---|
147 | recommended to perform a full backup (which can be used for
|
---|
148 | subsequent incremental backups) but if the amount of data is
|
---|
149 | too big an incremental backup will be sufficient, too. Which
|
---|
150 | strategy is sufficient for you depends on the amount of data
|
---|
151 | stored in your DB (is it a few hundret of table rows or is it
|
---|
152 | hundrets of Terabyte. A full backup of the later one isn't done
|
---|
153 | quickly (and we assume that the underlaying system of such a DB
|
---|
154 | might not be a home brewed LFS anyhow).
|
---|
155 | To close the last gap to fully protect your data, create a backup
|
---|
156 | of the corresponding old binaries (and/or their sources) and
|
---|
157 | store it along with the data files to
|
---|
158 | make sure that there is a fallback solution if it comes to
|
---|
159 | the situation that newer software might not be able to read
|
---|
160 | ancient data.</para>
|
---|
161 | </listitem>
|
---|
162 | <listitem>
|
---|
163 | <para>Upgrade the server software</para>
|
---|
164 | <para>In this step, instructions to build the database
|
---|
165 | server software are executed just as they are shown in
|
---|
166 | subsequent sections talking about the DBMs like MariaDB or
|
---|
167 | Postgresql. This is building the software as
|
---|
168 | it is been done as usual in the BLFS book.</para>
|
---|
169 | </listitem>
|
---|
170 | <listitem>
|
---|
171 | <para>Restore the database by using the new tools.</para>
|
---|
172 | <para>To restore the data, the tools of the newly installed
|
---|
173 | server software is used. During the restore process, the new
|
---|
174 | tools will create and/or upgrade the data files in the
|
---|
175 | format the software expects them to be. At this moment it is
|
---|
176 | assumed that newer software is capable to read old data.</para>
|
---|
177 | </listitem>
|
---|
178 | </itemizedlist>
|
---|
179 |
|
---|
180 | <para>
|
---|
181 | Since you have already a backup procedure in place (and you
|
---|
182 | have tested your restore procedure, don't you?), this way might
|
---|
183 | be the easiest way to upgrade as you are going to use your wellknown
|
---|
184 | processes to upgrade just as you allways do - at least in terms
|
---|
185 | of the backup and restore.
|
---|
186 | </para>
|
---|
187 |
|
---|
188 | </sect3>
|
---|
189 |
|
---|
190 | <sect3>
|
---|
191 | <title>Upgrade data file by using system tools</title>
|
---|
192 |
|
---|
193 | <para>
|
---|
194 | Some database systems (for instance Postgresql) provides
|
---|
195 | a tool which can reformat (=upgrade) the existing database
|
---|
196 | files to the new format. Since the upgrading tool has to
|
---|
197 | be used from the new server software (the old one cannot
|
---|
198 | know anything about a new file format), the old software
|
---|
199 | might be overwritten due to installation of the new software.
|
---|
200 | </para>
|
---|
201 |
|
---|
202 | <para>
|
---|
203 | In case you have to restore a backup (may be because running
|
---|
204 | the upgrade tool failed) you have to reinstall the old version
|
---|
205 | to get back the access to your data.
|
---|
206 | </para>
|
---|
207 |
|
---|
208 | <para>
|
---|
209 | Even though those tools might work one the actual database
|
---|
210 | files, it is still highly recommended to create a full backup
|
---|
211 | before running them. Any case of failure might result in a
|
---|
212 | serious damage of the database files.
|
---|
213 | </para>
|
---|
214 |
|
---|
215 | </sect3>
|
---|
216 |
|
---|
217 | </sect2>
|
---|
218 |
|
---|
219 | <sect2>
|
---|
220 | <title>Notes for specific DBMS</title>
|
---|
221 |
|
---|
222 | <sect3>
|
---|
223 | <title>PostgreSQL</title>
|
---|
224 |
|
---|
225 | <!-- might add some advanced notes for the DBMS here -->
|
---|
226 |
|
---|
227 | <para>Upstream documentation for Backup & Restore:
|
---|
228 | <ulink url="https://www.postgresql.org/docs/current/backup.html"/>
|
---|
229 | </para>
|
---|
230 |
|
---|
231 | </sect3>
|
---|
232 |
|
---|
233 | <sect3>
|
---|
234 | <title>MariaDB</title>
|
---|
235 |
|
---|
236 | <!-- might add some advanced notes for the DBMS here -->
|
---|
237 |
|
---|
238 | <para>Upstream documentation for Backup & Restore:
|
---|
239 | <ulink url="https://mariadb.com/kb/en/backup-and-restore-overview/"/>
|
---|
240 | </para>
|
---|
241 |
|
---|
242 | </sect3>
|
---|
243 |
|
---|
244 | <sect3>
|
---|
245 | <title>Sqlite</title>
|
---|
246 |
|
---|
247 | <!-- might add some advanced notes for the DBMS here -->
|
---|
248 |
|
---|
249 | <para>Don't underestimate <application>Sqlite</application>, it
|
---|
250 | is a feature rich DBMS. The main difference to the two big
|
---|
251 | players above is that Sqlite does not provide access via a
|
---|
252 | network API. Sqlite databases are files always stored on the
|
---|
253 | same machine as the running program which reads/writes the
|
---|
254 | database. The manipulation of data content is done via API calls
|
---|
255 | to library functions directly within the program.</para>
|
---|
256 |
|
---|
257 | <para>In the upstream documentation you may find the
|
---|
258 | following useful:</para>
|
---|
259 |
|
---|
260 | <para>Documentation of the sqlite3 command line tool:
|
---|
261 | <ulink url="https://www.sqlite.org/cli.html"/>
|
---|
262 | </para>
|
---|
263 | <para>Documentation of backup API calls:
|
---|
264 | <ulink url="https://www.sqlite.org/backup.html"/>
|
---|
265 | </para>
|
---|
266 |
|
---|
267 | <para>Unfortunatly, there is no dedicated chapter in the
|
---|
268 | upstream documentation talking about backup & restore but
|
---|
269 | there are several articles about it somewhere else in the
|
---|
270 | Internet. One example is shown below.</para>
|
---|
271 |
|
---|
272 | <para>Documentation for Backup & Restore:
|
---|
273 | <ulink url="https://database.guide/backup-sqlite-database/"/>
|
---|
274 | </para>
|
---|
275 |
|
---|
276 | </sect3>
|
---|
277 |
|
---|
278 | <sect3>
|
---|
279 | <title>Berkeley DB</title>
|
---|
280 |
|
---|
281 | <!-- might add some advanced notes for the DBMS here -->
|
---|
282 |
|
---|
283 | <para>Just like <application>Sqlite</application> this
|
---|
284 | software acts on local database files meaning there is no
|
---|
285 | network interface, too.</para>
|
---|
286 |
|
---|
287 | <para>The relevant resources for Backup & Restore a Berkeley DB
|
---|
288 | are the man pages for <filename>db_dump</filename> and its
|
---|
289 | counterpart <filename>db_load</filename>.</para>
|
---|
290 |
|
---|
291 | </sect3>
|
---|
292 | </sect2>
|
---|
293 |
|
---|
294 | </sect1>
|
---|