Here is the strace of guix-daemon: strace: Process 21446 attached select(4, [3], NULL, NULL, NULL) = 1 (in [3]) accept(3, {sa_family=AF_UNIX}, [128->2]) = 4 fcntl(4, F_GETFD) = 0 fcntl(4, F_SETFD, FD_CLOEXEC) = 0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = -1 EOPNOTSUPP (Operation not supported) setsockopt(4, SOL_TCP, TCP_QUICKACK, [1], 4) = -1 EOPNOTSUPP (Operation not supported) getsockopt(4, SOL_SOCKET, SO_PEERCRED, {pid=21666, uid=1000, gid=1000}, [12]) = 0 write(2, "accepted connection from pid 216"..., 46) = 46 clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f49fcf761d0) = 21672 strace: Process 21672 attached [pid 21446] close(4 [pid 21672] set_robust_list(0x7f49fcf761e0, 24 [pid 21446] <... close resumed> ) = 0 [pid 21672] <... set_robust_list resumed> ) = 0 [pid 21446] select(4, [3], NULL, NULL, NULL [pid 21672] close(3) = 0 [pid 21672] setsid() = 21672 [pid 21672] rt_sigaction(SIGCHLD, {sa_handler=SIG_DFL, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7f49fb8f2250}, {sa_handler=0x408f90, sa_mask=~[KILL STOP RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7f49fb8f2250}, 8) = 0 [pid 21672] rt_sigaction(SIGIO, {sa_handler=SIG_IGN, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7f49fb8f2250}, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0 [pid 21672] getpid() = 21672 [pid 21672] fcntl(4, F_SETOWN, 21672) = 0 [pid 21672] fcntl(4, F_GETFL) = 0x2 (flags O_RDWR) [pid 21672] fcntl(4, F_SETFL, O_RDWR|O_ASYNC) = 0 [pid 21672] read(4, "cxin\0\0\0\0", 32768) = 8 [pid 21672] write(4, "oixd\0\0\0\0a\1\0\0\0\0\0\0", 16) = 16 [pid 21672] read(4, "a\1\0\0\0\0\0\0", 32768) = 8 [pid 21672] --- SIGIO {si_signo=SIGIO, si_code=SI_KERNEL} --- [pid 21672] read(4, "\0\0\0\0\0\0\0\0\1\0\0\0\0\0\0\0", 32768) = 16 [pid 21672] rt_sigaction(SIGIO, {sa_handler=0x4096f0, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7f49fb8f2250}, {sa_handler=SIG_IGN, sa_mask=~[KILL STOP RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7f49fb8f2250}, 8) = 0 [pid 21672] select(5, [4], NULL, NULL, {tv_sec=0, tv_usec=0}) = 0 (Timeout) [pid 21672] lstat("/gnu/store", {st_dev=makedev(254, 0), st_ino=261483, st_mode=S_IFDIR|S_ISVTX|0775, st_nlink=812, st_uid=0, st_gid=999, st_blksize=4096, st_blocks=2864, st_size=1462272, st_atime=2018-01-30T05:08:01-0500.005440398, st_mtime=2018-01-30T21:58:20-0500.717328223, st_ctime=2018-01-30T21:58:20-0500.717328223}) = 0 [pid 21672] getuid() = 0 [pid 21672] statfs("/gnu/store", {f_type=EXT2_SUPER_MAGIC, f_bsize=4096, f_blocks=2370105, f_bfree=678352, f_bavail=552196, f_files=610800, f_ffree=439747, f_fsid={val=[1197410366, 3135970965]}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_RELATIME}) = 0 [pid 21672] lstat("/gnu/store/.links", {st_dev=makedev(254, 0), st_ino=261484, st_mode=S_IFDIR|0755, st_nlink=2, st_uid=0, st_gid=0, st_blksize=4096, st_blocks=29704, st_size=15196160, st_atime=2018-01-30T05:09:07-0500.734306527, st_mtime=2018-01-30T21:58:20-0500.657327505, st_ctime=2018-01-30T21:58:20-0500.657327505}) = 0 [pid 21672] lstat("/var/guix/profiles", {st_dev=makedev(254, 0), st_ino=261476, st_mode=S_IFDIR|0755, st_nlink=3, st_uid=0, st_gid=0, st_blksize=4096, st_blocks=8, st_size=4096, st_atime=2018-01-30T05:07:50-0500.201299582, st_mtime=1969-12-31T19:00:01-0500, st_ctime=2016-01-17T02:42:03-0500.994173793}) = 0 [pid 21672] lstat("/var/guix/temproots", {st_dev=makedev(254, 0), st_ino=261481, st_mode=S_IFDIR|0755, st_nlink=2, st_uid=0, st_gid=0, st_blksize=4096, st_blocks=8, st_size=4096, st_atime=2018-01-30T05:08:00-0500.989440189, st_mtime=2018-01-30T21:58:39-0500.313550723, st_ctime=2018-01-30T21:58:39-0500.313550723}) = 0 [pid 21672] lstat("/var/guix/db", {st_dev=makedev(254, 0), st_ino=261469, st_mode=S_IFDIR|0755, st_nlink=2, st_uid=0, st_gid=0, st_blksize=4096, st_blocks=8, st_size=4096, st_atime=2017-12-06T11:13:50-0500.709588501, st_mtime=2018-01-30T21:59:11-0500.449935220, st_ctime=2018-01-30T21:59:11-0500.449935220}) = 0 [pid 21672] lstat("/var/guix/gcroots", {st_dev=makedev(254, 0), st_ino=261474, st_mode=S_IFDIR|0755, st_nlink=3, st_uid=0, st_gid=0, st_blksize=4096, st_blocks=8, st_size=4096, st_atime=2018-01-30T05:07:50-0500.201299582, st_mtime=2017-07-24T03:33:04-0400.151020803, st_ctime=2017-07-24T03:33:04-0400.151020803}) = 0 [pid 21672] getuid() = 0 [pid 21672] lstat("/var/guix/profiles/per-user", {st_dev=makedev(254, 0), st_ino=261477, st_mode=S_IFDIR|S_ISVTX|0777, st_nlink=4, st_uid=0, st_gid=0, st_blksize=4096, st_blocks=8, st_size=4096, st_atime=2018-01-30T21:57:51-0500.636980272, st_mtime=2016-01-17T03:24:24-0500.763756302, st_ctime=2018-01-30T21:59:58-0500.434480564}) = 0 [pid 21672] chmod("/var/guix/profiles/per-user", 01777) = 0 [pid 21672] socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3 [pid 21672] connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory) [pid 21672] close(3) = 0 [pid 21672] socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3 [pid 21672] connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory) [pid 21672] close(3) = 0 [pid 21672] futex(0x7f49fbe86190, FUTEX_WAKE_PRIVATE, 2147483647) = 0 [pid 21672] rt_sigaction(SIGIO, {sa_handler=SIG_IGN, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7f49fb8f2250}, {sa_handler=0x4096f0, sa_mask=~[KILL STOP RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7f49fb8f2250}, 8) = 0 [pid 21672] write(4, "ptxc\0\0\0\0E\0\0\0\0\0\0\0the group `guixb"..., 96) = 96 [pid 21672] exit_group(0) = ? [pid 21672] +++ exited with 0 +++ <... select resumed> ) = ? ERESTARTNOHAND (To be restarted if no handler) --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=21672, si_uid=0, si_status=0, si_utime=0, si_stime=0} --- wait4(-1, NULL, WNOHANG, NULL) = 21672 wait4(-1, NULL, WNOHANG, NULL) = -1 ECHILD (No child processes) rt_sigreturn({mask=[]}) = -1 EINTR (Interrupted system call) select(4, [3], NULL, NULL, NULL