`postgresql` and some other reverse dependencies of `libandroid-shmem` do not work

tracker for libandroid-shmem support in termux-docker.

pkg upgrade
pkg install postgresql
mkdir $PREFIX/var/lib/postgresql
initdb $PREFIX/var/lib/postgresql

~ $ initdb $PREFIX/var/lib/postgresql
The files belonging to this database system will be owned by user "system".
This user must also own the server process.

The database cluster will be initialized with locale "C.UTF-8".
The default text search configuration will be set to "english".

Data page checksums are enabled.

fixing permissions on existing directory /data/data/com.termux/files/usr/var/lib/postgresql ... ok
creating subdirectories ... ok
selecting dynamic shared memory implementation ... mmap
selecting default "max_connections" ... 20
selecting default "shared_buffers" ... 400kB
selecting default time zone ... UTC
creating configuration files ... ok
running bootstrap script ... 2026-06-28 22:47:14.195 UTC [39441] FATAL:  could not create shared memory segment: No such file or directory
2026-06-28 22:47:14.195 UTC [39441] DETAIL:  Failed system call was shmget(key=98242661, size=56, 03600).
child process exited with exit code 1
initdb: removing contents of data directory "/data/data/com.termux/files/usr/var/lib/postgresql"

Related:

• https://github.com/termux/libandroid-shmem/issues/13

Reproduce the failure with the listed pkg, initdb, and PostgreSQL commands in the termux-docker environment. Then read the linked libandroid-shmem issue and trace how PostgreSQL's shared-memory call is handled; done means PostgreSQL initialization completes without the reported shmget failure.