Redhat and most major Linux distros such as Suse have adapted new Linux Kernel 3. Since release of Red Hat Enterprise Linux 7, Redhat replaces Linux Kernel 3 with the legacy kernel 2.6 in RHEL 6.7 and prior versions. Kernel 3 has improved handling of system services and runlevels. Kernel 2.6 System V "init" script for managing runlevels and "service", "chkconfig" commands for managing services have been replaced with "systemd" in Kernel 3.
Essential Commands:
I have collected a list of useful new commands to manage services, startup processes and runlevels for Linux Kernel 3.
Starting a service
Previously in RHEL 6 and prior:
# /etc/init.d/auditd start
Starting auditd: [ OK ]
Now in RHEL 7:
# systemctl start vsftpd.service
Stopping a service
Previously in RHEL 6 and prior:
# /etc/init.d/vsftpd stop
Stopping vsftpd: [ OK ]
# systemctl stop vsftpd.service
Check the service status
Previously in RHEL 6 and prior:
# /etc/init.d/vsftpd status
vsftpd (pid 1309) is running...
Now in RHEL 7:
# systemctl status vsftpd.service
vsftpd.service - Vsftpd ftp daemon
Loaded: loaded (/usr/lib/systemd/system/vsftpd.service; disabled)
Active: active (running) since Sat 2015-08-22 12:45:00 EDT; 12s ago
Process: 8217 ExecStart=/usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf (code=exited, status=0/SUCCESS)
Main PID: 8218 (vsftpd)
CGroup: /system.slice/vsftpd.service
└─8218 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
Aug 22 12:45:00 localhost.localdomain systemd[1]: Starting Vsftpd ftp daemon...
Aug 22 12:45:00 localhost.localdomain systemd[1]: Started Vsftpd ftp daemon.
Previously in RHEL 6 and prior:
# chkconfig vsftpd on
Now in RHEL 7:
# systemctl enable vsftpd.service
ln -s '/usr/lib/systemd/system/vsftpd.service' '/etc/systemd/system/multi-user.target.wants/vsftpd.service'
Disable a service at boot
Previously in RHEL 6 and prior:
# chkconfig vsftpd off
Now in RHEL 7:
# systemctl disable vsftpd.service
rm '/etc/systemd/system/multi-user.target.wants/vsftpd.service'
Show list of services starting during boot
Previously in RHEL 6 and prior:
# chkconfig --list
NetworkManager 0:off 1:off 2:on 3:on 4:on 5:on 6:off
abrt-ccpp 0:off 1:off 2:off 3:on 4:off 5:on 6:off
abrtd 0:off 1:off 2:off 3:on 4:off 5:on 6:off
acpid 0:off 1:off 2:on 3:on 4:on 5:on 6:off
atd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
auditd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
autofs 0:off 1:off 2:off 3:on 4:on 5:on 6:off
blk-availability 0:off 1:on 2:on 3:on 4:on 5:on 6:off
certmonger 0:off 1:off 2:off 3:on 4:on 5:on 6:off
cpuspeed 0:off 1:on 2:on 3:on 4:on 5:on 6:off
crond 0:off 1:off 2:on 3:on 4:on 5:on 6:off
Now in RHEL 7:
# systemctl list-unit-files –type=service
UNIT FILE STATE
abrt-ccpp.service enabled
abrt-oops.service enabled
abrt-pstoreoops.service disabled
abrt-vmcore.service enabled
abrt-xorg.service enabled
abrtd.service enabled
accounts-daemon.service enabled
alsa-restore.service static
alsa-state.service static
alsa-store.service static
anaconda-direct.service static
anaconda-nm-config.service static
anaconda-noshell.service static
anaconda-shell@.service static
anaconda-sshd.service static
anaconda-tmux@.service static
anaconda.service static
arp-ethers.service disabled
atd.service enabled
auditd.service enabled
auth-rpcgss-module.service static
autovt@.service disabled
Show the current runlevel(now "target")
systemd uses 'targets' instead of runlevels. By default, there are two main targets:
multi-user.target: former runlevel 3
graphical.target: former runlevel 5
Previously in RHEL 6 and prior:
# cat /etc/inittab
id:5:initdefault:
Now in RHEL 7:
# systemctl get-default
multi-user.target
Change the default runlevel(target)
To change from runlevel 3 to 5(target multi-user.target to graphical.target),
Previously in RHEL 6 and prior change the runlevel number in inittab file, e.g. from runlevel 5 to 3:
# cat /etc/inittab
id:3:initdefault:
Now in RHEL 7 the location of default runlevel is in "/etc/systemd/system/default.target" and it can be set by following command:
# systemctl set-default graphical.target
rm '/etc/systemd/system/default.target'
ln -s '/usr/lib/systemd/system/graphical.target' '/etc/systemd/system/default.target'
# systemctl get-default
graphical.target
graphical.target
Although legacy commands are still supported in RHEL 7 for time being for compatibility reasons but they may not have full power and will discounted in near future.
Legacy commands have been provided with a hint to new commands. e.g:
# chkconfig --list
Note: This output shows SysV services only and does not include native
systemd services. SysV configuration data might be overridden by native
systemd configuration.
If you want to list systemd services use 'systemctl list-unit-files'.
To see services enabled on particular target use
'systemctl list-dependencies [target]'.
netconsole 0:off 1:off 2:off 3:off 4:off 5:off 6:off
network 0:off 1:off 2:on 3:on 4:on 5:on 6:off
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