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AKB

2017-Jan-13 04:15 UTC

Rsync tries to access unnecessary files/dirs after chrooting itself.

Hi.

While debugging some encfs errors in the logs, I realized they are
being generated because rsync (chrooted inside a encfs file system,
--reverse) is trying to access files like: /root/.popt, /etc/localtime
etc. This doesn't seem to be related to ID-name mapping as I already
have numeric ids enabled in config. Here is the relevant strace
output:

[pid 25549] chroot("/chroot")           = 0
[pid 25549] chdir("/")                  = 0
[pid 25549] setgid(0)                   = 0
[pid 25549] setgroups(1, [0])           = 0
[pid 25549] setuid(0)                   = 0
[pid 25549] setresuid(-1, 0, -1)        = 0
[pid 25549] geteuid()                   = 0
[pid 25549] write(3, "@RSYNCD: OK\n", 12) = 12
[pid 25549] select(4, [3], NULL, [3], {60, 0}) = 1 (in [3], left {59, 961500})
[pid 25549] read(3, "-", 1)             = 1
...........
...........
[pid 25549] select(4, [3], NULL, [3], {60, 0}) = 1 (in [3], left {59, 999994})
[pid 25549] read(3, "\0", 1)            = 1
[pid 25549] open("/usr/etc/popt", O_RDONLY) = -1 ENOENT (No such file
or directory)
[pid 25549] open("/etc/popt", O_RDONLY) = -1 ENOENT (No such file or
directory)
[pid 25549] stat("/etc/popt.d", 0x7ffdf53cf1c0) = -1 ENOENT (No such
file or directory)
[pid 25549] open("/root/.popt", O_RDONLY) = -1 ENOENT (No such file or
directory)
[pid 25549] stat("/etc/localtime", 0x7ffdf53cd4e0) = -1 ENOENT (No
such file or directory)
[pid 25549] open("/etc/localtime", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No
such file or directory)
[pid 25549] write(4, "2017/01/13 03:44:20 [25549] rsyn"..., 86) = 86
[pid 25549] fcntl(3, F_GETFL)           = 0x802 (flags O_RDWR|O_NONBLOCK)
[pid 25549] fcntl(3, F_GETFL)           = 0x802 (flags O_RDWR|O_NONBLOCK)
[pid 25549] write(3, "\16", 1)          = 1
[pid 25549] write(3, "\24MxX", 4)       = 4
[pid 25549] brk(0x7fef0557c000)         = 0x7fef0557c000
[pid 25549] select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 883408})
[pid 25549] read(3, "\4\0\0\7\0\0\0\0", 32768) = 8
[pid 25549] open("/etc/localtime", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No
such file or directory)
[pid 25549] write(4, "2017/01/13 03:44:20 [25549] buil"..., 47) = 47
[pid 25549] chdir("/")                  = 0
[pid 25549] lstat(".", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
[pid 25549] mmap(NULL, 266240, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fef05033000
[pid 25549] mmap(NULL, 266240, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fef04f55000
[pid 25549] openat(AT_FDCWD, ".",
O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
[pid 25549] getdents(5, /* 2 entries */, 32768) = 48
[pid 25549] getdents(5, /* 0 entries */, 32768) = 0
[pid 25549] close(5)                    = 0
[pid 25549] select(4, [3], [3], [3], {60, 0}) = 1 (out [3], left {59, 999991})
[pid 25549] write(3, "\17\0\0\7\31\1.\0\0\20X\374Kx\355A\0\0\0", 19) =
19
[pid 25549] select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 960181})
[pid 25549] read(3, "\1\0\0\7\0", 32768) = 5
[pid 25549] select(4, [3], [3], [3], {60, 0}) = 1 (out [3], left {59, 999993})
[pid 25549] write(3, "\1\0\0\7\0", 5)   = 5
[pid 25549] select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 961272})
[pid 25549] read(3, "\2\0\0\7\0\0", 32768) = 6
[pid 25549] select(4, [3], [3], [3], {60, 0}) = 1 (out [3], left {59, 999993})
[pid 25549] write(3, "\2\0\0\7\0\0", 6) = 6
[pid 25549] select(4, [3], [3], [3], {60, 0}) = 1 (out [3], left {59, 999994})
[pid 25549] write(3, "\17\0\0\7\0\23\0\0\36\0\0\0\0\0\1\0\0\0\0", 19)
= 19
[pid 25549] select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 883181})
[pid 25549] read(3, "\1\0\0\7\0", 32768) = 5
[pid 25549] rt_sigaction(SIGUSR1, {SIG_IGN, [], SA_RESTORER,
0x7fef043e50e0}, NULL, 8) = 0
[pid 25549] rt_sigaction(SIGUSR2, {SIG_IGN, [], SA_RESTORER,
0x7fef043e50e0}, NULL, 8) = 0
[pid 25549] open("/etc/localtime", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No
such file or directory)
[pid 25549] write(4, "2017/01/13 03:44:20 [25549] sent"..., 75) = 75

Can this be prevented on rsync side? On every access to a non-existing
file/dir, the underlying fs (encfs) generates a error in the logs.

Thanks.

AKB

2017-Jan-13 13:13 UTC

head link

Rsync tries to access unnecessary files/dirs after chrooting itself.

Please ignore. The issue wasn't rsync's fault. Rsync daemon was being
launched from a different process using execv which resulted in these side
effects. Rsync launched on its own is working as expected.

-----Original Message-----
From: rsync [mailto:rsync-bounces at lists.samba.org] On Behalf Of AKB
Sent: Friday, January 13, 2017 9:45 AM
To: rsync at lists.samba.org
Subject: Rsync tries to access unnecessary files/dirs after chrooting itself.

Hi.

While debugging some encfs errors in the logs, I realized they are being
generated because rsync (chrooted inside a encfs file system,
--reverse) is trying to access files like: /root/.popt, /etc/localtime etc. This
doesn't seem to be related to ID-name mapping as I already have numeric ids
enabled in config. Here is the relevant strace
output:

[pid 25549] chroot("/chroot")           = 0
[pid 25549] chdir("/")                  = 0
[pid 25549] setgid(0)                   = 0
[pid 25549] setgroups(1, [0])           = 0
[pid 25549] setuid(0)                   = 0
[pid 25549] setresuid(-1, 0, -1)        = 0
[pid 25549] geteuid()                   = 0
[pid 25549] write(3, "@RSYNCD: OK\n", 12) = 12 [pid 25549] select(4,
[3], NULL, [3], {60, 0}) = 1 (in [3], left {59, 961500})
[pid 25549] read(3, "-", 1)             = 1
...........
...........
[pid 25549] select(4, [3], NULL, [3], {60, 0}) = 1 (in [3], left {59, 999994})
[pid 25549] read(3, "\0", 1)            = 1
[pid 25549] open("/usr/etc/popt", O_RDONLY) = -1 ENOENT (No such file
or directory) [pid 25549] open("/etc/popt", O_RDONLY) = -1 ENOENT (No
such file or directory) [pid 25549] stat("/etc/popt.d",
0x7ffdf53cf1c0) = -1 ENOENT (No such file or directory) [pid 25549]
open("/root/.popt", O_RDONLY) = -1 ENOENT (No such file or
directory)
[pid 25549] stat("/etc/localtime", 0x7ffdf53cd4e0) = -1 ENOENT (No
such file or directory) [pid 25549] open("/etc/localtime",
O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) [pid 25549] write(4,
"2017/01/13 03:44:20 [25549] rsyn"..., 86) = 86
[pid 25549] fcntl(3, F_GETFL)           = 0x802 (flags O_RDWR|O_NONBLOCK)
[pid 25549] fcntl(3, F_GETFL)           = 0x802 (flags O_RDWR|O_NONBLOCK)
[pid 25549] write(3, "\16", 1)          = 1
[pid 25549] write(3, "\24MxX", 4)       = 4
[pid 25549] brk(0x7fef0557c000)         = 0x7fef0557c000
[pid 25549] select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 883408})
[pid 25549] read(3, "\4\0\0\7\0\0\0\0", 32768) = 8 [pid 25549]
open("/etc/localtime", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file
or directory) [pid 25549] write(4, "2017/01/13 03:44:20 [25549]
buil"..., 47) = 47
[pid 25549] chdir("/")                  = 0
[pid 25549] lstat(".", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
[pid 25549] mmap(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0x7fef05033000 [pid 25549] mmap(NULL, 266240, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fef04f55000 [pid 25549] openat(AT_FDCWD,
".", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5 [pid 25549]
getdents(5, /* 2 entries */, 32768) = 48 [pid 25549] getdents(5, /* 0 entries
*/, 32768) = 0
[pid 25549] close(5)                    = 0
[pid 25549] select(4, [3], [3], [3], {60, 0}) = 1 (out [3], left {59, 999991})
[pid 25549] write(3, "\17\0\0\7\31\1.\0\0\20X\374Kx\355A\0\0\0", 19) =
19 [pid 25549] select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 960181})
[pid 25549] read(3, "\1\0\0\7\0", 32768) = 5 [pid 25549] select(4,
[3], [3], [3], {60, 0}) = 1 (out [3], left {59, 999993})
[pid 25549] write(3, "\1\0\0\7\0", 5)   = 5
[pid 25549] select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 961272})
[pid 25549] read(3, "\2\0\0\7\0\0", 32768) = 6 [pid 25549] select(4,
[3], [3], [3], {60, 0}) = 1 (out [3], left {59, 999993}) [pid 25549] write(3,
"\2\0\0\7\0\0", 6) = 6 [pid 25549] select(4, [3], [3], [3], {60, 0}) =
1 (out [3], left {59, 999994}) [pid 25549] write(3,
"\17\0\0\7\0\23\0\0\36\0\0\0\0\0\1\0\0\0\0", 19) = 19 [pid 25549]
select(4, [3], [], [3], {60, 0}) = 1 (in [3], left {59, 883181}) [pid 25549]
read(3, "\1\0\0\7\0", 32768) = 5 [pid 25549] rt_sigaction(SIGUSR1,
{SIG_IGN, [], SA_RESTORER, 0x7fef043e50e0}, NULL, 8) = 0 [pid 25549]
rt_sigaction(SIGUSR2, {SIG_IGN, [], SA_RESTORER, 0x7fef043e50e0}, NULL, 8) = 0
[pid 25549] open("/etc/localtime", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No
such file or directory) [pid 25549] write(4, "2017/01/13 03:44:20 [25549]
sent"..., 75) = 75

Can this be prevented on rsync side? On every access to a non-existing file/dir,
the underlying fs (encfs) generates a error in the logs.

Thanks.

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