[Pkg-libvirt-maintainers] Bug#787973: Please don't use systemctl status in postinst

[Michael Biebl]

Package: libvirt-daemon-system
Version: 1.2.16-2
Severity: normal

Hi,

I noticed the following in postinst:

        # Force virtlockd to reexec if enabled
        if [ -d /run/systemd/system ] && systemctl status virtlockd.service >/dev/null; then
           systemctl reload virtlockd.service
        fi


using systemctl status is bad, since it accesses the journal, which can
be quite costly.
If you only want to test if a service is active, you can use
systemctl is-active -q virtlockd.service, which is much more
lightweight.
The -q makes sure, you don't need to suppress stdout.

if [ -d /run/systemd/system ] && systemctl is-active -q virtlockd.service ; then
           systemctl reload virtlockd.service
        fi

Or even simpler for your use case
        if [ -d /run/systemd/system ] ; then
           systemctl reload-or-try-restart -q virtlockd.service
        fi

I think reload-or-try-restart does already exactly what you want.

Cheers,
Michael

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'stable'), (200, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.0.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.utf8, LC_CTYPE=de_DE.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libvirt-daemon-system depends on:
ii  adduser              3.113+nmu3
ii  gettext-base         0.19.4-1
ii  init-system-helpers  1.23
ii  libapparmor1         2.9.2-3
ii  libaudit1            1:2.4-1+b1
ii  libavahi-client3     0.6.31-5
ii  libavahi-common3     0.6.31-5
ii  libblkid1            2.26.2-6
ii  libc6                2.19-18
ii  libcap-ng0           0.7.6-1
ii  libdbus-1-3          1.8.18-1
ii  libdevmapper1.02.1   2:1.02.90-2.2
ii  libgnutls-deb0-28    3.3.15-5
ii  libnl-3-200          3.2.24-2
ii  libnl-route-3-200    3.2.24-2
ii  libnuma1             2.0.10-1
ii  librados2            0.80.9-2
ii  librbd1              0.80.9-2
ii  libsasl2-2           2.1.26.dfsg1-13
ii  libselinux1          2.3-2
ii  libssh2-1            1.5.0-2+b1
ii  libsystemd0          220-5~test0
ii  libvirt-clients      1.2.16-2
ii  libvirt-daemon       1.2.16-2
ii  libvirt0             1.2.16-2
ii  libxen-4.4           4.4.1-9
ii  libxml2              2.9.2+dfsg1-3
ii  libyajl2             2.1.0-2
ii  logrotate            3.8.7-2
ii  policykit-1          0.105-8

Versions of packages libvirt-daemon-system recommends:
ii  bridge-utils  1.5-9
ii  dmidecode     2.12-4
ii  dnsmasq-base  2.72-3.1+b1
ii  ebtables      2.0.10.4-3
ii  iproute2      3.16.0-2
ii  iptables      1.4.21-2+b1
ii  parted        3.2-7
pn  pm-utils      <none>

Versions of packages libvirt-daemon-system suggests:
pn  apparmor    <none>
pn  auditd      <none>
ii  nfs-common  1:1.2.8-9
ii  radvd       1:2.11-1
ii  systemd     220-5~test0
pn  systemtap   <none>

-- Configuration Files:
/etc/libvirt/qemu.conf [Errno 13] Keine Berechtigung: u'/etc/libvirt/qemu.conf'
/etc/libvirt/qemu/networks/default.xml [Errno 13] Keine Berechtigung: u'/etc/libvirt/qemu/networks/default.xml'

-- no debconf information