配置文件详解

[Journal]
#Storage=persistent
Storage=persistent
#Compress=yes
#Seal=yes
#SplitMode=uid
#SyncIntervalSec=5m
#RateLimitInterval=30s
#RateLimitBurst=1000
#SystemMaxUse=
#SystemKeepFree=
#SystemMaxFileSize=
#RuntimeMaxUse=
#RuntimeKeepFree=
#RuntimeMaxFileSize=
#MaxRetentionSec=
#MaxFileSec=1month
ForwardToSyslog=yes
ForwardToKMsg=no
ForwardToConsole=no
#ForwardToWall=yes
#TTYPath=/dev/console
MaxLevelStore=debug
MaxLevelSyslog=debug
MaxLevelKMsg=notice
MaxLevelConsole=info
#MaxLevelWall=emerg

SplitMode:Controls whether to split up journal files per user. One of "uid", "login" and "none". If "uid", all users will get each their own journal
           files regardless of whether they possess a login session or not, however system users will log into the system journal. If "login", actually
           logged-in users will get each their own journal files, but users without login session and system users will log into the system journal. If
           "none", journal files are not split up by user and all messages are instead stored in the single system journal. Note that splitting up journal
           files by user is only available for journals stored persistently. If journals are stored on volatile storage (see above), only a single journal
           file for all user IDs is kept. Defaults to "uid".

Seal:默认开启，保护journal file日志文件不会被篡改，sealing key可以通过：journalctl(1)'s --setup-keys命令获得，Forward Secure Sealing (FSS) for all persistent journal files is enabled.

SYSLOG(3)

Journal Export Format

Note that this document describes the binary serialization format of journals only, as used for transfer across the network. For interfacing with web technologies there's the Journal JSON Format. The binary format on disk is documented as Journal File Format. Before reading on, please make sure you are aware of the basic properties of journal entries, in particular realize that they may include binary non-text data (though usually don't), and the same field might have multiple values assigned within the same entry (though usually hasn't).

这么看journal有几种格式：

  • ‘binary serialization format’，also 'Journal Export Format',used for transfer across the network
  • 'Journal JSON Format',For interfacing with web technologies
  • 'binary format ',he binary format on disk is documented as Journal File Format

systemd-journald行为方式

lsof -p $(pidof /usr/lib/systemd/systemd-journald)

[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#cat /etc/systemd/journald.conf
[Journal]
Storage=persistent
#Compress=yes
#Seal=yes
#SplitMode=uid
#SyncIntervalSec=5m
#RateLimitInterval=30s
#RateLimitBurst=1000
#SystemMaxUse=
#SystemKeepFree=
SystemMaxFileSize=8M
SystemMaxFiles=4
#RuntimeMaxUse=
#RuntimeKeepFree=
#RuntimeMaxFileSize=
#MaxRetentionSec=
#MaxFileSec=1month
ForwardToSyslog=yes
ForwardToKMsg=no
ForwardToConsole=no
#ForwardToWall=yes
#TTYPath=/dev/console
MaxLevelStore=debug
MaxLevelSyslog=debug
MaxLevelKMsg=notice
MaxLevelConsole=info
#MaxLevelWall=emerg

SystemMaxFiles 参数貌似没有起到作用！！！

[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#ll
total 180280
-rw-r-----  1 root root 8388608 Sep 13 17:23 system@95b85109e44b4ea89ce66e094c94279b-0000000000004e88-00053c5ff5809def.journal
-rw-r-----  1 root root 8388608 Sep 13 17:25 system@95b85109e44b4ea89ce66e094c94279b-0000000000006e68-00053c602bb61502.journal
-rw-r-----  1 root root 8388608 Sep 13 17:27 system@95b85109e44b4ea89ce66e094c94279b-0000000000009f12-00053c60322d04c3.journal
-rw-r-----  1 root root 8388608 Sep 13 17:29 system@95b85109e44b4ea89ce66e094c94279b-000000000000cb31-00053c6038479d6c.journal
-rw-r-----  1 root root 8388608 Sep 13 17:29 system@95b85109e44b4ea89ce66e094c94279b-000000000000f4be-00053c603ebe24f1.journal
-rw-r-----  1 root root 8388608 Sep 13 17:30 system@95b85109e44b4ea89ce66e094c94279b-000000000001160d-00053c6041a0db53.journal
-rw-r-----  1 root root 8388608 Sep 13 17:31 system@95b85109e44b4ea89ce66e094c94279b-0000000000013963-00053c6045174c27.journal
-rw-r-----  1 root root 8388608 Sep 13 17:32 system@95b85109e44b4ea89ce66e094c94279b-00000000000158cf-00053c604839c78f.journal
-rw-r-----  1 root root 8388608 Sep 13 17:33 system@95b85109e44b4ea89ce66e094c94279b-0000000000016f16-00053c6049a0781f.journal
-rw-r-----  1 root root 8388608 Sep 13 17:33 system@95b85109e44b4ea89ce66e094c94279b-0000000000019a25-00053c604e8e6c3e.journal
-rw-r-----  1 root root 8388608 Sep 13 17:35 system@95b85109e44b4ea89ce66e094c94279b-000000000001a953-00053c604eca2bf0.journal
-rw-r-----  1 root root 8388608 Sep 13 17:37 system@95b85109e44b4ea89ce66e094c94279b-000000000001d162-00053c6054d3d62b.journal
-rw-r-----  1 root root 8388608 Sep 13 17:39 system@95b85109e44b4ea89ce66e094c94279b-000000000001fb55-00053c605bd49733.journal
-rw-r-----  1 root root 8388608 Sep 13 17:40 system.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:23 user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000004ef3-00053c5ffc035f5e.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:29 user-120063@eca90592d5664b05b2105e0c4e422d85-000000000000d096-00053c60386fd583.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:30 user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000012a78-00053c60434097e3.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:33 user-120063@eca90592d5664b05b2105e0c4e422d85-00000000000176ad-00053c604a4e7164.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:39 user-120063@eca90592d5664b05b2105e0c4e422d85-000000000001fda6-00053c605c2d0517.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:40 user-120063.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:23 user-122575@a0ae95f91a2f430d8869228a5c1d142f-0000000000004eb3-00053c5ff957f41a.journal
-rw-r-----+ 1 root root 8388608 Sep 13 17:40 user-122575.journal

[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#du -sh *
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000004e88-00053c5ff5809def.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000006e68-00053c602bb61502.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000009f12-00053c60322d04c3.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000000cb31-00053c6038479d6c.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000000f4be-00053c603ebe24f1.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001160d-00053c6041a0db53.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000013963-00053c6045174c27.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-00000000000158cf-00053c604839c78f.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000016f16-00053c6049a0781f.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000019a25-00053c604e8e6c3e.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001a953-00053c604eca2bf0.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001d162-00053c6054d3d62b.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001fb55-00053c605bd49733.journal
8.1M    system.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000004ef3-00053c5ffc035f5e.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000000d096-00053c60386fd583.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000012a78-00053c60434097e3.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-00000000000176ad-00053c604a4e7164.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000001fda6-00053c605c2d0517.journal
8.0M    user-120063.journal
8.0M    user-122575@a0ae95f91a2f430d8869228a5c1d142f-0000000000004eb3-00053c5ff957f41a.journal
8.0M    user-122575.journal

前面SystemMaxFileSize=8M，

现在修改为如下：

SystemMaxFileSize=20M，然后执行：systemctl daemon-reload;systemctl restart systemd-journald;

继续狂打日志：for i in seq 1 20000;do logger -p authpriv.info hello$i;done

按照我的猜想，后面的文件最大，应该只有20M左右了吧，于是开始打日志，打了一会儿，发现还是8M，多打一会儿日志后，后面滚动的文件大小确实差不多是20M了，看来不是立即生效，很让人费解；

如下，你可以看到滚动后产生的靠近20M的文件了，但是，还是不知道究竟什么时候开始删除之前的文件；究竟可以保存多少个文件？？？

[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#du -sh *
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000004e88-00053c5ff5809def.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000006e68-00053c602bb61502.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000009f12-00053c60322d04c3.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000000cb31-00053c6038479d6c.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000000f4be-00053c603ebe24f1.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001160d-00053c6041a0db53.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000013963-00053c6045174c27.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-00000000000158cf-00053c604839c78f.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000016f16-00053c6049a0781f.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000019a25-00053c604e8e6c3e.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001a953-00053c604eca2bf0.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001d162-00053c6054d3d62b.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-000000000001fb55-00053c605bd49733.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000022537-00053c6062d58196.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000024f10-00053c6069d64213.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-00000000000278e2-00053c6070d787d1.journal
17M     system@95b85109e44b4ea89ce66e094c94279b-000000000002a1a4-00053c607a097db8.journal
8.0M    system.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000004ef3-00053c5ffc035f5e.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000000d096-00053c60386fd583.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000012a78-00053c60434097e3.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-00000000000176ad-00053c604a4e7164.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000001fda6-00053c605c2d0517.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000024151-00053c60674ac34c.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000026981-00053c606e1343f0.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000002a927-00053c607ff1def4.journal
8.0M    user-120063.journal
8.0M    user-122575@a0ae95f91a2f430d8869228a5c1d142f-0000000000004eb3-00053c5ff957f41a.journal
8.0M    user-122575.journal

另外发现，之前将journal文件改为persistent后，/run/log/journal/613fd1717b844226af5ea83f4849d6dd目录下的文件的数量并没有随即自动删除。

root@srmbuffer010242252156.cloud.dg /run/log/journal/613fd1717b844226af5ea83f4849d6dd]
#systemctl status systemd-journald
● systemd-journald.service - Journal Service
   Loaded: loaded (/usr/lib/systemd/system/systemd-journald.service; static; vendor preset: disabled)
   Active: active (running) since Tue 2016-09-13 17:47:23 CST; 12min ago
     Docs: man:systemd-journald.service(8)
           man:journald.conf(5)
 Main PID: 53736 (systemd-journal)
   Status: "Processing requests..."
   CGroup: /system.slice/systemd-journald.service
           └─53736 /usr/lib/systemd/systemd-journald

Sep 13 17:47:23 srmbuffer010242252156.cloud.dg systemd-journal[53736]: Permanent journal is using 216.0M (max allowed 4.0G, trying to leave 4.0G free…t 4.0G).
Sep 13 17:47:23 srmbuffer010242252156.cloud.dg systemd-journal[53736]: Journal started

当前可以发现，现在已经使用了216.0M ，但是最多可以使用4.0G；

于是，我们修改：

SystemMaxUse=100M

看看什么报错：

#systemctl daemon-reload;
#systemctl restart systemd-journald
[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#systemctl status systemd-journald
● systemd-journald.service - Journal Service
   Loaded: loaded (/usr/lib/systemd/system/systemd-journald.service; static; vendor preset: disabled)
   Active: active (running) since Tue 2016-09-13 18:02:15 CST; 6s ago
     Docs: man:systemd-journald.service(8)
           man:journald.conf(5)
 Main PID: 5270 (systemd-journal)
   Status: "Processing requests..."
   CGroup: /system.slice/systemd-journald.service
           └─5270 /usr/lib/systemd/systemd-journald

Sep 13 18:02:15 srmbuffer010242252156.cloud.dg systemd-journal[5270]: Permanent journal is using 264.0M (max allowed 100.0M, trying to leave 4.0G fre…264.0M).
Sep 13 18:02:15 srmbuffer010242252156.cloud.dg systemd-journal[5270]: Journal started

结果，发现没有什么报错，反而是/var/log/journal/目录下的，老旧的文件被删除了；

[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#du -sh *
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000022537-00053c6062d58196.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-0000000000024f10-00053c6069d64213.journal
8.1M    system@95b85109e44b4ea89ce66e094c94279b-00000000000278e2-00053c6070d787d1.journal
17M     system@95b85109e44b4ea89ce66e094c94279b-000000000002a1a4-00053c607a097db8.journal
17M     system@95b85109e44b4ea89ce66e094c94279b-000000000002c796-00053c608966f4f5.journal
8.1M    system.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000001fda6-00053c605c2d0517.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000024151-00053c60674ac34c.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-0000000000026981-00053c606e1343f0.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000002a927-00053c607ff1def4.journal
8.0M    user-120063@eca90592d5664b05b2105e0c4e422d85-000000000002c9a0-00053c608b0fc119.journal
8.0M    user-120063.journal
8.0M    user-122575.journal

[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#du -sh /var/log/journal/613fd1717b844226af5ea83f4849d6dd
121M    /var/log/journal/613fd1717b844226af5ea83f4849d6dd

按照这个逻辑，我继续写大量日志，应该找个目录大小不会增加了吧。只会删除老旧文件：

测试一下：

[root@srmbuffer010242252156.cloud.dg /var/log/journal/613fd1717b844226af5ea83f4849d6dd]
#for i in `seq 1 20000`;do logger -p authpriv.info test$i;done
Sep 13 18:41:35 srmbuffer010242252156.cloud.dg systemd-journal[5270]: Suppressed 18998 messages from /user.slice/user-122575.slice

哟呵，日志被抑制了；不过，看来，日志文件有多少个，是根据总的可用空间决定；比如：我们只有SystemMaxUse=100M可用空间，SystemMaxFileSize=20M设置单个journal文件大小只有20的话，那基本上只会保存5个历史文件左右；

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