SUBGID(5)

📦
version 4.20.0.arch1 · 19 versions
, in arch rolling

💖 SUBGID(5) — the vibe ✨

okay bestie, welcome to the subgid manual page, aka the configuration for subordinate group ids. it lives in the File Formats and Configuration corner of the manual-verse and honestly? it's giving underrated icon. let's get into it 🫶

🌸 NAME 🌸

subgid — the configuration for subordinate group ids. that's it, that's the name, periodt.

✨ DESCRIPTION ✨

so. Subgid authorizes a group id to map ranges of group ids from its namespace into child namespaces. yes queen, delegation. 💅

the delegation of the subordinate gids can be configured via the subid field in the /etc/nsswitch.conf file. and listen — only one value can be set as the delegation source. one. singular. main character only. 👑

  • setting this field to files configures the delegation of gids to /etc/subgid
  • setting any other value treats the delegation as a plugin, following with a name of the form libsubid_$value.so
  • if the value or plugin is missing, then the subordinate gid delegation falls back to files (she's resilient, she's fine, she recovers 💅)
⚠️ note bestie, and this is important: newusers, useradd, and usermod will only create entries in /etc/subgid if subid delegation is managed via subid files. no files, no entries. simple as that. 🎀

🌈 LOCAL SUBORDINATE DELEGATION 🌈

each line in /etc/subgid contains a user name and a range of subordinate group ids that user is allowed to use. and it's specified with three fields delimited by colons (":"). the three fields are:

  • login name or UID
  • numerical subordinate group ID
  • numerical subordinate group ID count

that's it. three little colon-separated besties holding the whole thing together. 🥹

this file specifies the group IDs that ordinary users can use, with the newgidmap command, to configure gid mapping in a user namespace. iykyk. 🔥

multiple ranges may be specified per user — go off, stack them ranges, she can hold more than one. ✨

😭 okay but here's the cautionary tale: when large number of entries (10000-100000 or more) are defined in /etc/subgid, parsing performance penalty will become noticeable. in this case it is recommended to use UIDs instead of login names. benchmarks have shown speed-ups up to 20x. twenty. times. faster. that's not a vibe check, that's a whole vibe upgrade. 🚀

🎀 FILES 🎀

  • /etc/subgid — Per user subordinate group IDs.
  • /etc/subgid- — Backup file for /etc/subgid.

👑 SEE ALSO 👑

login.defs(5), newgidmap(1), newuidmap(1), newusers(8), subuid(5), useradd(8), userdel(8), usermod(8), user_namespaces(7).

and that's the whole page, bestie!! you ate this read fr fr 💖 this little masterpiece is brought to you by shadow-utils 4.20.0, dated 07/30/2026 — mwah, love u, go configure some subordinate group ids responsibly 🦋🌸

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