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logind: make sure there's always a getty available on TTY6
Previously, if X allocated all 6 TTYs (for multi-session for example) no getty would be available anymore to guarantee console-based logins. With the new ReserveVT= switch in logind.conf we can now choose one VT (6 by default) that will always be subject to autovt-style activation, i.e. we'll always have a getty on TTY6, and X will never take possession of it.
This commit is contained in:
Lennart Poettering
parent
4db17f291c
commit
98a77df5fe
4
TODO
4
TODO
@ -55,10 +55,10 @@ F18:
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* selinux: merge systemd selinux access controls (dwalsh)
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* make logind reserve tty6 or so for text logins, so that gdm never picks it up
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Features:
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* move cryptsetup key caching into kernel keyctl?
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* make nspawn work without terminal
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* hw watchdog: optionally try to use the preset watchdog timeout instead of always overriding it
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@ -71,14 +71,15 @@
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<listitem><para>Takes a positive
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integer. Configures how many virtual
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terminals to allocate by default that
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-- when switched to --
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terminals (VTs) to allocate by default
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that -- when switched to and
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previously unused --
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<literal>autovt</literal> services are
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automatically spawned on. These
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services are instantiated from the
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template
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template unit
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<filename>autovt@.service</filename>
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with the virtual terminal TTY name,
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for the respective VT TTY name,
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e.g. <filename>autovt@tty4.service</filename>. By
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default
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<filename>autovt@.service</filename>
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@ -86,15 +87,49 @@
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<filename>getty@.service</filename>,
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i.e. login prompts are started
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dynamically as the user switches to
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unused virtual terminals. This
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parameter hence controls how many
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gettys are available on the virtual
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terminals. Defaults to 6. When set to
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unused virtual terminals. Hence, this
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parameter controls how many login
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<literal>gettys</literal> are
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available on the VTs. If a VT is
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already used by some other subsystem
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(for example a graphical login) this
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kind of activation will not be
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attempted. Note that the VT configured
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in <varname>ReserveVT=</varname> is
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always subject to this kind of
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activation, even if it is not one of
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VTs configured with the
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<varname>NAutoVTs=</varname>
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directive. Defaults to 6. When set to
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0, automatic spawning of
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<literal>autovt</literal> services is
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disabled. </para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>ReserveVT=</varname></term>
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<listitem><para>Takes a positive
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integer. Configures the number of one
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virtual terminal that shall
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unconditionally be reserved for
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<filename>autovt@.service</filename>
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activation (see above). The VT
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selected with this option will be
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marked busy unconditionally so that no
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other subsystem will allocate it. This
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functionality is useful to ensure that
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regardless how many VTs are allocated
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by other subsystems one login
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<literal>getty</literal> is always
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available. Defaults to 6 (with other
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words: there'll always be a
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<literal>getty</literal> available on
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Alt-F6.). When set to 0, VT
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reservation is
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disabled.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>KillUserProcesses=</varname></term>
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@ -15,6 +15,7 @@ struct ConfigPerfItem;
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%includes
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%%
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Login.NAutoVTs, config_parse_unsigned, 0, offsetof(Manager, n_autovts)
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Login.ReserveVT, config_parse_unsigned, 0, offsetof(Manager, reserve_vt)
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Login.KillUserProcesses, config_parse_bool, 0, offsetof(Manager, kill_user_processes)
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Login.KillOnlyUsers, config_parse_strv, 0, offsetof(Manager, kill_only_users)
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Login.KillExcludeUsers, config_parse_strv, 0, offsetof(Manager, kill_exclude_users)
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@ -50,8 +50,10 @@ Manager *manager_new(void) {
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m->udev_vcsa_fd = -1;
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m->udev_button_fd = -1;
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m->epoll_fd = -1;
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m->reserve_vt_fd = -1;
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m->n_autovts = 6;
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m->reserve_vt = 6;
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m->inhibit_delay_max = 5 * USEC_PER_SEC;
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m->handle_power_key = HANDLE_NO_SESSION;
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m->handle_sleep_key = HANDLE_TTY_SESSION;
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@ -166,6 +168,9 @@ void manager_free(Manager *m) {
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if (m->epoll_fd >= 0)
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close_nointr_nofail(m->epoll_fd);
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if (m->reserve_vt_fd >= 0)
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close_nointr_nofail(m->reserve_vt_fd);
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strv_free(m->controllers);
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strv_free(m->reset_controllers);
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strv_free(m->kill_only_users);
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@ -948,20 +953,28 @@ int manager_spawn_autovt(Manager *m, int vtnr) {
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assert(m);
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assert(vtnr >= 1);
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if ((unsigned) vtnr > m->n_autovts)
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if ((unsigned) vtnr > m->n_autovts &&
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(unsigned) vtnr != m->reserve_vt)
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return 0;
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if ((unsigned) vtnr != m->reserve_vt) {
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/* If this is the reserved TTY, we'll start the getty
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* on it in any case, but otherwise only if it is not
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* busy. */
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r = vt_is_busy(vtnr);
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if (r < 0)
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return r;
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else if (r > 0)
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return -EBUSY;
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}
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if (asprintf(&name, "autovt@tty%i.service", vtnr) < 0) {
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log_error("Could not allocate service name.");
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r = -ENOMEM;
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goto finish;
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}
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r = bus_method_call_with_reply (
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m->bus,
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"org.freedesktop.systemd1",
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@ -980,6 +993,26 @@ finish:
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return r;
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}
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static int manager_reserve_vt(Manager *m) {
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_cleanup_free_ char *p = NULL;
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assert(m);
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if (m->reserve_vt <= 0)
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return 0;
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if (asprintf(&p, "/dev/tty%u", m->reserve_vt) < 0)
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return log_oom();
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m->reserve_vt_fd = open(p, O_RDWR|O_NOCTTY|O_CLOEXEC|O_NONBLOCK);
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if (m->reserve_vt_fd < 0) {
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log_warning("Failed to pin reserved VT: %m");
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return -errno;
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}
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return 0;
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}
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int manager_get_session_by_cgroup(Manager *m, const char *cgroup, Session **session) {
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Session *s;
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char *p;
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@ -1450,6 +1483,9 @@ int manager_startup(Manager *m) {
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/* Remove stale objects before we start them */
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manager_gc(m, false);
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/* Reserve the special reserved VT */
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manager_reserve_vt(m);
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/* And start everything */
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HASHMAP_FOREACH(seat, m->seats, i)
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seat_start(seat);
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@ -9,6 +9,7 @@
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[Login]
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#NAutoVTs=6
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#ReserveVT=6
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#KillUserProcesses=no
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#KillOnlyUsers=
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#KillExcludeUsers=root
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@ -68,6 +68,9 @@ struct Manager {
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unsigned n_autovts;
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unsigned reserve_vt;
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int reserve_vt_fd;
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Seat *vtconsole;
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char *cgroup_path;
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