我已经使用 rsnapshot 很多年了，从来没有遇到过问题，但我搞不清楚这个问题。版本是 1.4.2。
我在 rsnapshot.conf 中有以下内容：
retain alpha 8
retain beta 7
retain gamma 8
retain delta 12
..以及 crontab 中的以下内容：
0 11,12,14,16,18,20 * * * /usr/bin/rsnapshot alpha
00 22 * * * /usr/bin/rsnapshot beta
30 2 * * 5 /usr/bin/rsnapshot gamma
00 6 1 * * /usr/bin/rsnapshot delta
Beta 版和 alpha 版作业运行完美：
root@host1:/Backup/rsnapshot_backups# ls -lt
drwxr-xr-x+ 3 root root 4096 Oct 30 18:06 alpha.0
drwxr-xr-x+ 3 root root 4096 Oct 30 16:09 alpha.1
drwxr-xr-x+ 3 root root 4096 Oct 30 14:14 alpha.2
drwxr-xr-x+ 3 root root 4096 Oct 30 12:10 alpha.3
drwxr-xr-x+ 3 root root 4096 Oct 30 11:09 alpha.4
drwxr-xr-x+ 3 root root 4096 Oct 29 20:06 alpha.5
drwxr-xr-x+ 3 root root 4096 Oct 29 18:06 alpha.6
drwxr-xr-x+ 3 root root 4096 Oct 29 16:09 alpha.7
drwxr-xr-x+ 3 root root 4096 Oct 28 18:10 beta.0
drwxr-xr-x+ 3 root root 4096 Oct 27 18:06 beta.1
drwxr-xr-x+ 3 root root 4096 Oct 26 18:08 beta.2
drwxr-xr-x+ 3 root root 4096 Oct 25 18:09 beta.3
drwxr-xr-x+ 3 root root 4096 Oct 24 18:12 beta.4
drwxr-xr-x+ 3 root root 4096 Oct 23 18:16 beta.5
drwxr-xr-x+ 3 root root 4096 Oct 22 18:23 beta.6
但是 gamma 和 delta 从未运行。我做错了什么？
来自 rsnapshot.log：
[2017-10-27T02:30:02] /usr/bin/rsnapshot gamma: started
[2017-10-27T02:30:02] echo 2250 > /var/run/rsnapshot.pid
[2017-10-27T02:30:02] /Backup/rsnapshot_backups/beta.6 not present (yet), nothing to copy
[2017-10-27T02:30:02] rm -f /var/run/rsnapshot.pid
[2017-10-27T02:30:02] /usr/bin/rsnapshot gamma: completed successfully
它抱怨无法找到 beta.6 但我已经确认该目录存在。