我们已经知道，centos7上建议使用sytemd进行资源限制。
本文主要介绍如何使用systemd进行用户级资源限制。
以orange用户为例。
方案一 临时有效
配置如下：
# systemctl set-property user-1000.slice MemoryLimit=200M
# systemctl daemon-reload一般情况下，以上设置就可以了。
但有时还是会遇到以下问题：
# systemctl set-property user-1000.slice MemoryLimit=200M
Failed to set unit properties on user-1000.slice: Unit user-1000.slice is not loaded.
User with id 1007 not logged in. First login as that user then set limits解决办法
首先使用
# systemctl start user-1000.slice再进行设置
# systemctl set-property user-1000.slice MemoryLimit=200M
# systemctl daemon-reload方案二 永久生效
首先，编写slice文件user-1000.slice
其中1000是orange用户的uid，可用命令查看
# id -u username文件内容如下
[Unit]
Description=orange user.slice
[Slice]
MemoryAccounting=true
MemoryLimit=200M其次，拷贝到指定位置
# cp user-1000.slice /usr/lib/systemd/system启用
# systemctl start user-1000.slice重新加载配置
# systemctl daemon-reload查看系统中的slice
# systemctl -t slice
UNIT LOAD ACTIVE SUB DESCRIPTION
-.slice loaded active active Root Slice
system-getty.slice loaded active active system-getty.slice
system-selinux\x2dpolicy\x2dmigrate\x2dlocal\x2dchanges.slice loaded active active system-selinux\x2dpolicy\x2dmigrate\x2dlocal\x2dchanges.slice
system.slice loaded active active System Slice
user-0.slice loaded active active User Slice of root
user-1000.slice loaded active active orange user.slice
user.slice loaded active active User and Session Slice
LOAD = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB = The low-level unit activation state, values depend on unit type.
7 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.查看某个具体的slice
# systemctl status user-1000.slice -l
● user-1000.slice - orange user.slice
Loaded: loaded (/usr/lib/systemd/system/user-1000.slice; static; vendor preset: disabled)
Drop-In: /etc/systemd/system/user-1000.slice.d
└─50-MemoryLimit.conf
Active: active since 四 2018-08-02 15:17:01 CST; 1min 40s ago
Memory: 1.5M (limit: 200.0M)
CGroup: /user.slice/user-1000.slice
└─session-14973.scope
└─56361 /export/servers/orange-agent/orange-guard/orange-guard -c cfg.json
8月 02 15:17:01 A02-R05-I79-201-3V98WK2.ORANGE.LOCAL systemd[1]: Created slice orange user.slice.
8月 02 15:17:01 A02-R05-I79-201-3V98WK2.ORANGE.LOCAL systemd[1]: Starting orange user.slice.
8月 02 15:17:01 A02-R05-I79-201-3V98WK2.ORANGE.LOCAL CROND[56324]: (orange) CMD (`which taskset` -c `source /export/servers/orange-agent/run_cpus.sh && cpus` /export/servers/orange-agent/super_guard.sh >> /export/servers/orange-agent/orange-agent/var/app.log 2>&1 &)
8月 02 15:18:01 A02-R05-I79-201-3V98WK2.ORANGE.LOCAL CROND[56925]: (orange) CMD (`which taskset` -c `source /export/servers/orange-agent/run_cpus.sh && cpus` /export/servers/orange-agent/super_guard.sh >> /export/servers/orange-agent/orange-agent/var/app.log 2>&1 &)经过以上设置后，orange用户启动的所有进程占用的物理内存之和不能超过200M，如果超过，进程机会被kill。
如果进程因为OOM被kill，会在/var/log/message中发现记录。
如何查看某个进程受哪些资源限制条件
# cat /proc/PID/cgroup
11:memory:/user-1000.slice
10:perf_event:/
9:devices:/user.slice
8:hugetlb:/
7:blkio:/user.slice
6:cpuset:/
5:freezer:/
4:pids:/
3:cpuacct,cpu:/user.slice
2:net_prio,net_cls:/
1:name=systemd:/user.slice/user-1000.slice/session-8569.scope参考
centos7 user.slice
https://stackoverflow.com/questions/47367886/cgroup-configuration-in-centos-7
centos 7 systemd资源限制举例
https://www.certdepot.net/rhel7-get-started-cgroups/
Table 10.1. Available systemd Unit Types
Table 10.2. Systemd Unit Files Locations
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/chap-managing_services_with_systemd
service文件参考
/usr/lib/systemd/system/ssh.service