我配置了以下参数，但重新启动后，这些值返回到预览值。
如何将它们配置为永久？
echo 500 > /proc/sys/vm/dirty_expire_centisecs
echo 3 > /proc/sys/vm/dirty_background_ratio
echo 100 > /proc/sys/vm/dirty_writeback_centisecs
顺便说一句，该文件中不存在参数
more /etc/sysctl.conf
# /etc/sysctl.conf
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
kernel.shmall = 5767168
kernel.shmmax = 4294967295
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
fs.file-max = 6815744
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default = 1048576
net.core.rmem_max = 4194304
net.core.wmem_default = 1048576
net.core.wmem_max = 4194304
net.ipv4.ip_local_port_r