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我正在尝试执行 apt-get upgrade 命令，但出现以下错误:
Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/^(.*?)(\\)?\${ <-- HERE ([^{}]+)}(.*)$/ at /usr/share/perl5/Debconf/Question.pm line 72.
Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\${ <-- HERE ([^}]+)}/ at /usr/share/perl5/Debconf/Config.pm line 30.
Extracting templates from packages: 100%
Preconfiguring packages ...
Setting up hostname (3.16ubuntu2) ...
insserv: warning: script 'friendly-recovery' missing LSB tags and overrides
insserv: Default-Start undefined, assuming empty start runlevel(s) for script `friendly-recovery'
insserv: Default-Stop undefined, assuming empty stop runlevel(s) for script `friendly-recovery'
insserv: warning: script 'cron' missing LSB tags and overrides
insserv: Default-Start undefined, assuming empty start runlevel(s) for script `cron'
insserv: Default-Stop undefined, assuming empty stop runlevel(s) for script `cron'
insserv: warning: script 'sshd' missing LSB tags and overrides
insserv: script sshd: service sshd already provided!
insserv: There is a loop between service monit and sshd if stopped
insserv: loop involving service sshd at depth 2
insserv: loop involving service monit at depth 1
insserv: Stopping ssh depends on monit and therefore on system facility `$all' which can not be true!
insserv: exiting now without changing boot order!
update-rc.d: error: insserv rejected the script header
dpkg: error processing package hostname (--configure):
subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
hostname
E: Sub-process /usr/bin/dpkg returned an error code (1)
请帮我解决一下。这是服务器，我的所有操作都停滞不前。