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user-sessions: do not remove /etc/nologin

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pam_nologin looks for /etc/nologin and /run/nologin.
user-sessions creates (and removes) /run/nologin, but also removes
/etc/nologin. (This behaviour is unchanged since the introduction
of the binary in e92787416c691c3f34f47349e5eae3fa68eae856.)

By not removing pam_nologin we fully drop compatibility with PAM < 1.1.
This has the advantage that now /etc/nologin can be used by administrator to
disable user logins, e.g. for extended maintanance. We already specified
PAM >= 1.1.2 as dependency, so this was already covered.

The makes the code match the man page.

Fixes #26965.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2023-03-25 11:34:47 +01:00 committed by Lennart Poettering
parent dc2b3f9469
commit a78413baae
2 changed files with 14 additions and 11 deletions
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12
src/shared/fileio-label.c
View File

@ -23,9 +23,15 @@ int write_string_file_atomic_label_ts(const char *fn, const char *line, struct t
int create_shutdown_run_nologin_or_warn(void) {
int r;
/* This is used twice: once in systemd-user-sessions.service, in order to block logins when we actually go
* down, and once in systemd-logind.service when shutdowns are scheduled, and logins are to be turned off a bit
* in advance. We use the same wording of the message in both cases. */
/* This is used twice: once in systemd-user-sessions.service, in order to block logins when we
* actually go down, and once in systemd-logind.service when shutdowns are scheduled, and logins are
* to be turned off a bit in advance. We use the same wording of the message in both cases.
*
* Traditionally, there was only /etc/nologin, and we managed that. Then, in PAM 1.1
* support for /run/nologin was added as alternative
* (https://github.com/linux-pam/linux-pam/commit/e9e593f6ddeaf975b7fe8446d184e6bc387d450b).
* 13 years later we stopped managing /etc/nologin, leaving it for the administrator to manage.
*/
r = write_string_file_atomic_label("/run/nologin",
"System is going down. Unprivileged users are not permitted to log in anymore. "

13
src/user-sessions/user-sessions.c
View File

@ -15,7 +15,7 @@
#include "string-util.h"
static int run(int argc, char *argv[]) {
int r, k;
int r;
if (argc != 2)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
@ -29,14 +29,11 @@ static int run(int argc, char *argv[]) {
if (r < 0)
return r;
if (streq(argv[1], "start")) {
r = unlink_or_warn("/run/nologin");
k = unlink_or_warn("/etc/nologin");
if (r < 0)
return r;
return k;
/* We only touch /run/nologin. See create_shutdown_run_nologin_or_warn() for details. */
} else if (streq(argv[1], "stop"))
if (streq(argv[1], "start"))
return unlink_or_warn("/run/nologin");
if (streq(argv[1], "stop"))
return create_shutdown_run_nologin_or_warn();
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Unknown verb '%s'.", argv[1]);