URL:
https://github.com/SSSD/sssd/pull/5370
Title: #5370: nss: Use posix_fallocate() to alloc memcache file
deastoe commented:
"""
With the repro described on the ticket, we now observe the failures in sssd_nss.log but
sssd_nss successfully starts up without memcache functionality.
```
(2020-10-14 16:05:59): [nss] [sss_mmap_cache_init] (0x0100): Fast 'PASSWD' mmap
cache: timeout = 300, slots = 209712
(2020-10-14 16:05:59): [nss] [sss_mmap_cache_init] (0x0020): Failed to allocate file
/var/lib/sss/mc/passwd: 28(No space left on device)
(2020-10-14 16:05:59): [nss] [setup_memcaches] (0x0020): Failed to initialize passwd mmap
cache: 'No space left on device'
(2020-10-14 16:05:59): [nss] [sss_mmap_cache_init] (0x0100): Fast 'GROUP' mmap
cache: timeout = 300, slots = 157284
(2020-10-14 16:05:59): [nss] [sss_mmap_cache_init] (0x0020): Failed to allocate file
/var/lib/sss/mc/group: 28(No space left on device)
(2020-10-14 16:05:59): [nss] [setup_memcaches] (0x0020): Failed to initialize group mmap
cache: 'No space left on device'
(2020-10-14 16:05:59): [nss] [sss_mmap_cache_init] (0x0100): Fast 'INITGROUPS'
mmap cache: timeout = 300, slots = 262140
(2020-10-14 16:05:59): [nss] [sss_mmap_cache_init] (0x0020): Failed to allocate file
/var/lib/sss/mc/initgroups: 28(No space left on device)
(2020-10-14 16:05:59): [nss] [setup_memcaches] (0x0020): Failed to initialize initgroups
mmap cache: 'No space left on device'
```
```
sudo systemctl status sssd
● sssd.service - System Security Services Daemon
Loaded: loaded (/lib/systemd/system/sssd.service; disabled; vendor preset: enabled)
Active: active (running) since Wed 2020-10-14 16:05:59 GMT; 5min ago
Main PID: 17576 (sssd)
Tasks: 3 (limit: 2362)
CPU: 65ms
CGroup: /system.slice/sssd.service
├─17576 /usr/sbin/sssd -i --logger=files
├─17577 /usr/libexec/sssd/sssd_be --domain foo --uid 0 --gid 0 --logger=files
└─17578 /usr/libexec/sssd/sssd_nss --uid 0 --gid 0 --logger=files
```
"""
See the full comment at
https://github.com/SSSD/sssd/pull/5370#issuecomment-708518591