Centos7中修改主机名的方法

hostname临时修改主机名

hostname XXX

hostnamectl永久修改主机名

hostnamectl XXX

修改的内容实际是文件/etc/hostname

三种主机名的区别

man hostnamectl
This tool distinguishes three different hostnames: 
the high-level "pretty" hostname which might include all kinds of special characters (e.g. "Lennart's Laptop"), 
the static hostname which is used to initialize the kernel hostname at boot (e.g. "lennarts-laptop"), 
and the transient hostname which is a default received from network configuration. If a static hostname is set, and is valid (something other than localhost), then the transient hostname is not used.

Centos7中，hostnamectl --static命令读取的实际是/etc/hostname文件的内容

hostnamectl源码参考：https://github.com/systemd/systemd
hostnamectl --static函数调用梳理如下：

DEFINE_MAIN_FUNCTION(run);
hostnamectl_main func table
get_or_set_hostname
get_hostname_based_on_flag
get_one_name(bus, "StaticHostname", NULL);
sd_bus_get_property
sd_bus_call_method
sd_bus_call_methodv();
static const BusObjectImplementation manager_object = {
        "/org/freedesktop/hostname1",
        "org.freedesktop.hostname1",
        .vtables = BUS_VTABLES(hostname_vtable),
};
hostname_vtable
SD_BUS_PROPERTY("StaticHostname", "s", property_get_static_hostname, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE)
property_get_static_hostname 
context_read_etc_hostname
read_etc_hostname
int read_etc_hostname(const char *path, char **ret) {
        _cleanup_fclose_ FILE *f = NULL;
        assert(ret);
        if (!path)
                path = "/etc/hostname";
        f = fopen(path, "re");
        if (!f)
                return -errno;
        return read_etc_hostname_stream(f, ret);
}

可以看出，最终调用read_etc_hostname读取/etc/hostname的内容