Обратился клиент с проблемой неработающих бекапов в ISPmanager 5 Lite. Для выяснения проблемы, смотрим логи панели управления, которые отвечают за бекап, соответственно:

/usr/local/mgr5/var/backup2_cgi.log  
/usr/local/mgr5/var/backup2_cp.log  
/usr/local/mgr5/var/backup2_import.log 
/usr/local/mgr5/var/backup2.log  
/usr/local/mgr5/var/backup2_system.log

Искал так

grep ERROR /usr/local/mgr5/var/backup2*.log  

В моем случае я обошелся проверкой только /usr/local/mgr5/var/backup2.log и следом /usr/local/mgr5/var/backup2_cp.log

Как выявилось, проблема элементарна — на удаленном хранилище закончилось дисковое пространство

Jun 18 04:39:35 [16061:1] main INFO Put /usr/local/mgr5/var/backup/ispmgr/******.tgz.part1
Jun 18 04:39:35 [27034:1] main ERROR No disk space left on storage. Size limit: 106300440576
Jun 18 04:40:35 [27034:1] main ERROR No disk space left on storage. Size limit: 106300440576
Jun 18 04:41:35 [27034:1] main ERROR No disk space left on storage. Size limit: 106300440576
Jun 18 04:41:36 [16982:1] libmgr EXTINFO Command line argument 'path' add value 'var/backup/ispmgr'
Jun 18 04:41:36 [16982:1] libmgr EXTINFO Command line argument 'date' add value '2018-06-18'
Jun 18 04:41:36 [16982:1] libmgr EXTINFO Command line argument 'size-limit' add value '106300440576'
Jun 18 04:41:36 [16982:1] libmgr EXTINFO Command line argument 'count-limit' add value '7:7'
Jun 18 04:41:36 [16982:1] main INFO Size control server is ready. Date: 2018-06-18
Jun 18 04:42:20 [17872:1] libmgr EXTINFO Command line argument 'info-file' add value 'var/backup/ispmgr/******/2018-06-18/2018-06-18.******.info.******'
Jun 18 04:42:20 [27034:1] main ERROR No disk space left on storage. Size limit: 106300440576
Jun 18 04:43:20 [18247:1] libmgr EXTINFO Command line argument 'info-file' add value 'var/backup/ispmgr/******/2018-06-18/2018-06-18.******.info.mJMC9y'
Jun 18 04:43:20 [18247:1] main INFO Put /usr/local/mgr5/var/backup/ispmgr/******/2018-06-18/******.tgz.part1
Jun 18 04:43:20 [27034:1] main ERROR No disk space left on storage. Size limit: 106300440576
Jun 18 04:44:20 [27034:1] main ERROR No disk space left on storage. Size limit: 106300440576
Jun 18 04:44:20 [18698:1] main INFO Delete /usr/local/mgr5/var/backup/ispmgr/******/2018-06-18/2018-06-18.******.info.mJMC9y
Jun 18 04:44:21 [18705:1] libmgr EXTINFO Command line argument 'path' add value 'var/backup/ispmgr'
Jun 18 04:44:21 [18705:1] libmgr EXTINFO Command line argument 'date' add value '2018-06-18'
Jun 18 04:44:21 [18705:1] libmgr EXTINFO Command line argument 'size-limit' add value '106300440576'
Jun 18 04:44:21 [18705:1] libmgr EXTINFO Command line argument 'count-limit' add value '7:7'
Jun 18 04:44:21 [18705:1] main INFO Size control server is ready. Date: 2018-06-18
Jun 18 04:47:27 [20060:1] libmgr EXTINFO Command line argument 'info-file' add value 'var/backup/ispmgr/******/2018-06-18/2018-06-18.******.PqHjzO'
Jun 18 04:49:27 [27034:1] main ERROR No disk space left on storage. Size limit: 106300440576