ACCESS.CONF(5)

✨ NAME ✨

okay so bestie, access.conf is the login access control table file — it's literally the guest list at the door of your system, deciding who gets in and who gets politely told "no 💅". This is the access.conf(5) page from the Linux-PAM Manual, and yes it's iconic, we're getting into it. 🎀

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🌸 DESCRIPTION 🌸

The /etc/security/access.conf file specifies (user/group, host), (user/group, network/netmask), (user/group, tty), (user/group, X-$DISPLAY-value), or (user/group, pam-service-name) combinations for which a login will be either accepted or refused. That's the whole vibe. 🫶

When someone logs in, the file access.conf is scanned for the first entry that matches the (user/group, host) or (user/group, network/netmask) combination, or, in case of non-networked logins, the first entry that matches the (user/group, tty) combination, or in the case of non-networked logins without a tty, the first entry that matches the (user/group, X-$DISPLAY-value) or (user/group, pam-service-name/) combination. The permissions field of that table entry determines whether the login will be accepted or refused. First match wins, no takebacks. 😤

Each line of the login access control table has three fields separated by a ":" character (colon):

permission:users/groups:origins

Let's break down the trio, one by one 🦋:

• The first field, the permission field, can be either a "+" character (plus) for access granted or a "-" character (minus) for access denied. Yes, it's literally just a plus or a minus. Slay.
• The second field, the users/group field, should be a list of one or more login names, group names, uid, gid, or ALL (which always matches). To differentiate user entries from group entries, group entries should be written with brackets, e.g. (group) or (gid).
• The third field, the origins field, should be a list of one or more tty names (for non-networked logins), X $DISPLAY values or PAM service names (for non-networked logins without a tty), host names, domain names (begin with "."), host addresses, internet network numbers (end with "."), internet network addresses with network mask (where network mask can be a decimal number or an internet address also), ALL (which always matches) or LOCAL.

vibe check on LOCAL: the LOCAL keyword matches when the user connects without a network connection (e.g., su, login). A connection through the loopback device (e.g., ssh user@localhost) is considered a network connection, and thus, the LOCAL keyword does not match. sorry bestie, localhost is not "local" here, it's giving network. 💀

If supported by the system you can use @netgroupname in host or user patterns. The @@netgroupname syntax is supported in the user pattern only and it makes the local system hostname to be passed to the netgroup match call in addition to the user name. This might not work correctly on some libc implementations causing the match to always fail. 🙈

The EXCEPT operator makes it possible to write very compact rules. Obsessed.

If the nodefgroup is not set, the group file is searched when a name does not match that of the logged-in user. Only groups are matched in which users are explicitly listed. However the PAM module does not look at the primary group id of a user. (iykyk 👑)

The "#" character at start of line (no space at front) can be used to mark this line as a comment line. Note the "no space at front" part — that's not a suggestion, that's the rules. 😭

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💖 EXAMPLES 💖

These are some example lines which might be specified in /etc/security/access.conf. Copy the energy, not the mistakes 🧚

User root should be allowed to get access via cron, X11 terminal :0, tty1, ..., tty5, tty6.

+:root:crond :0 tty1 tty2 tty3 tty4 tty5 tty6

User root should be allowed to get access from hosts which own the IPv4 addresses. This does not mean that the connection have to be a IPv4 one, a IPv6 connection from a host with one of this IPv4 addresses does work, too. (no cap, that's the actual behaviour ✨)

+:root:192.168.200.1 192.168.200.4 192.168.200.9

+:root:127.0.0.1

User root should get access from network 192.168.201. where the term will be evaluated by string matching. But it might be better to use network/netmask instead. The same meaning of 192.168.201. is 192.168.201.0/24 or 192.168.201.0/255.255.255.0.

+:root:192.168.201.

User root should be able to have access from hosts foo1.bar.org and foo2.bar.org (uses string matching also).

+:root:foo1.bar.org foo2.bar.org

User root should be able to have access from domain foo.bar.org (uses string matching also).

+:root:.foo.bar.org

User root should be denied to get access from all other sources.

-:root:ALL

A user with uid 1003 and a group with gid 1000 should be allowed to get access from all other sources.

+:(1000) 1003:ALL

User foo and members of netgroup admins should be allowed to get access from all sources. This will only work if netgroup service is available.

+:@admins foo:ALL

User john and foo should get access from IPv6 host address.

+:john foo:2001:db8:0:101::1

User john and foo should get access from IPv6 link local host address.

+:john foo:fe80::de95:818c:1b55:7e42%eth1

User john should get access from IPv6 net/mask.

+:john:2001:db8:0:101::/64

Members of group wheel should be allowed to get access from all sources.

+:(wheel):ALL

Disallow console logins to all but the shutdown, sync and all other accounts, which are a member of the wheel group.

-:ALL EXCEPT (wheel) shutdown sync:LOCAL

All other users should be denied to get access from all sources.

-:ALL:ALL

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🦋 NOTES 🦋

The default separators of list items in a field are space, ',', and tabulator characters. Thus conveniently if spaces are put at the beginning and the end of the fields they are ignored. However if the list separator is changed with the listsep option, the spaces will become part of the actual item and the line will be most probably ignored. For this reason, it is not recommended to put spaces around the ':' characters. learn from our pain bestie 😭

An IPv6 link local host address must contain the interface identifier. IPv6 link local network/netmask is not supported.

Hostnames should be written as Fully-Qualified Host Name (FQHN) to avoid confusion with device names or PAM service names.

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🎀 SEE ALSO 🎀

pam_access(8), pam.d(5), pam(8)

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👑 AUTHORS 👑

Original login.access(5) manual was provided by Guido van Rooij which was renamed to access.conf(5) to reflect relation to default config file. iconic glow-up honestly.

Network address / netmask description and example text was introduced by Mike Becher <mike.becher@lrz-muenchen.de>. 💜

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and that's the whole page, bestie!! this came from [FIXME: source], dated 09/27/2026 — go forth and gatekeep your logins responsibly 🌈⭐🫶