sync
A Linux system account: what it is, and which numbers it holds.
What this account is
Both distributions give this account /bin/sync as its login shell rather than an interactive one, so a session opened under it writes out pending filesystem changes and then ends. Debian places it at UID 4 in group 65534, nogroup, with home directory /bin; Alpine places it at UID 5 in group 0, root, with home directory /sbin. Whether such a login can be completed at all is not settled by this row. It depends on the password field in /etc/shadow and on how login services and PAM are configured. /etc/shells does not list this shell; some services consult that list and others ignore it.
Source: base-passwd 3.6.8 (passwd); alpine-baselayout passwd and group, aports; /etc/shells. Read 2026-08-08.
Sources
| Distribution | Source package | Package version | Commit | Read from source |
|---|---|---|---|---|
| Debian | base-passwd | 3.6.8 | a080557e1d59 | 2026-08-07 |
| Alpine Linux | alpine-baselayout | 3.7.2 | a9c597c5cee0 | 2026-08-07 |