Linux journald相关
[root@compute-2 ~]# cat /etc/os-release NAME="CentOS Linux" VERSION="7 (Core)" ID="centos" ID_LIKE="rhel fedora" VERSION_ID="7" PRETTY_NAME="CentOS Linux 7 (Core)" ANSI_COLOR="0;31" CPE_NAME="cpe:/o:centos:centos:7" HOME_URL="https://www.centos.org/" BUG_REPORT_URL="https://bugs.centos.org/" CENTOS_MANTISBT_PROJECT="CentOS-7" CENTOS_MANTISBT_PROJECT_VERSION="7" REDHAT_SUPPORT_PRODUCT="centos" REDHAT_SUPPORT_PRODUCT_VERSION="7" [root@compute-2 ~]# cat /etc/redhat-release CentOS Linux release 7.6.1810 (Core)
Links
https://www.freedesktop.org/software/systemd/man/journalctl.html
Save journal to files
- 令 journald 保存到文件中
默认journald保存到 /run/log/journal 下面,由于/run是个临时空间
所以该保存策略只有本次开机后的日志
对于某些场景的日志记录不足以满足需求(如机器异常关机,重新开机读取不了上一次的journal)
执行 mkdir /var/log/journal
等一会日志就会迁移到/var/log/journal下面了
不需要重启任何services
Save journal to /run/log
- 令 journald 只记录从开机后的信息到内存中,不保存到文件(默认)
systemctl stop systemd-journald.socket
systemctl stop systemd-journald.service
(注意区分先后顺序,先 stop systemd-journald.socket 再 stop systemd-journald.service )
因为
Warning: Stopping systemd-journald.service, but it can still be activated by: systemd-journald.socket
mv /var/log/journal /root/
systemctl start systemd-journald.socket
这时候 systemd-journald.service 应该也 be activated 了
journalctl --list-boots 也看到只有开机后的日志信息了(大误,是 systemctl start systemd-journald.socket 后的日志信息,因为旧的被迁走了 )
ps: 这种mv操作会导致 journal出现断层,也就是
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.
有一个能够弥补一点点的方法就是(毕竟 journal stop 掉的这个中间时间段,个人觉得日志是丢了的,没有去核对)
mv /var/log/journal /run/log/ systemctl start systemd-journald.socket journalctl --list-boots # 查看日志记录区间
其实 systemd-journald.socket 和 systemd-journald.service 其中一个执行 start 了另一个就会start了
Related environment variables
SYSTEMD_LESS
Override the options passed to less (by default "FRSXMK").
ssh 到linux节点后,export SYSTEMD_LESS=FRSMK
支持通过鼠标滚轮滑动查看 journal 日志
Related Commands
journalctl --list-boots
journalctl -b *********
journalctl -b ********* -n ***
journalctl -u **** # -u --unit=UNIT Show logs from the specified unit
journalctl -D #从指定目录读取日志文件(会被整合) -D --directory=PATH Show journal files from directory