|
12 | 12 | - It can be used to manage services such as **`START/STOP/RESTART/RELOAD`** as well as **`ENABLE/DISABLE`** services |
13 | 13 | during the system boot. |
14 | 14 | - It is also used to **`LIST AND MANAGE UNITS`** and **`LIST AND UPDATE TARGETS`** |
15 | | - |
| 15 | + |
16 | 16 |  |
17 | 17 |
|
18 | | - ### Systemctl Commands |
19 | | - |
20 | | - - To start a service use the start command, for example to start a docker service use **`systemctl start docker`** |
21 | | - |
22 | | - ``` |
23 | | - [~]$ systemctl start docker |
24 | | - ``` |
25 | | -
|
26 | | - - To stop a service use the stop command, for example to stop a docker service use **`systemctl stop docker`** |
27 | | - |
28 | | - ``` |
29 | | - [~]$ systemctl stop docker |
30 | | - ``` |
31 | | - - To restart a service use the restart command, for example to restart a docker service use **`systemctl restart docker`** this will stop and start again. |
32 | | -
|
33 | | - ``` |
34 | | - [~]$ systemctl restart docker |
35 | | - ``` |
36 | | - - To reload a service use the reload command, for example to reload a docker service use **`systemctl reload docker`**, this will reload all the configuration without interrupting the normal functionaltiy of the service |
37 | | - |
38 | | - ``` |
39 | | - [~]$ systemctl reload docker |
40 | | - ``` |
41 | | - - To enable a service and make it persistent accross reboots use the enable command, for example to enable a docker service use **`systemctl enable docker`** |
42 | | - |
43 | | - ``` |
44 | | - [~]$ systemctl enable docker |
45 | | - ``` |
46 | | -
|
47 | | - - To disable a service at boot use the disable command, for example to disable a docker service use **`systemctl disable docker`** command. |
48 | | - |
49 | | - ``` |
50 | | - [~]$ systemctl disable docker |
51 | | - ``` |
52 | | -
|
53 | | - - To know the status of the service use **`systemctl status docker`** command. This command provided the state of the service. If running properly is should show **`active (running)`** state as shown in screenshot below. |
54 | | - |
55 | | - ``` |
56 | | - [~]$ systemctl status docker |
57 | | - ``` |
58 | | -
|
59 | | - - Besides **`active (running)`** state there are few other state that you should be aware off. |
60 | | - |
61 | | -  |
62 | | -
|
63 | | - - Running **`systemctl daemon reload`** command after making changes to service unit file reloads the system manager configuration and makes the systemd aware of the changes. |
64 | | -
|
65 | | - - To edit the service file use command **`systemctl edit project-mercury.service --full`** this will open a text editor, you can make the changes and re-write the settings as needed, making changing this way applied immediately without running the **`systemctl daemon reload`** command |
66 | | - |
67 | | - ``` |
68 | | - [~]$ systemctl daemon-reload |
69 | | - ``` |
70 | | - ``` |
71 | | - [~]$ systemctl edit project-mercury.service --full |
72 | | - ``` |
73 | | - - To see the current runlevel use **`systemctl get-default`** |
74 | | - |
75 | | - ``` |
76 | | - [~]$ systemctl get default |
77 | | - ``` |
78 | | -
|
79 | | - - To change the runleve to a different target use **`systemctl set-default multi-user.target`** |
80 | | - |
81 | | - ``` |
82 | | - [~]$ systemctl set-default multi-user.target |
83 | | - ``` |
84 | | -
|
85 | | - - To list all the units that systemd has loaded use **`systemctl list-units --all`**, this lists all the unit which are active, inactive or anyother state. |
86 | | - |
87 | | - ``` |
88 | | - [~]$ systemctl list-units --all |
89 | | - ``` |
90 | | -
|
91 | | - - To list only active units use **`systemctl list-units`** command |
92 | | - |
93 | | - ``` |
94 | | - [~]$ systemctl list-units |
95 | | - ``` |
96 | | - |
97 | | -
|
98 | | - ## JOURNALCTL |
99 | | -
|
100 | | - - __Journalctl__ is a command for quering/viewing logs collected by systemd. |
101 | | - - The systemd-journald service is responsible for systemd’s log collection, and it retrieves messages from the kernel systemd services, and other sources. |
102 | | - - Very useful when you are troubleshooting issues with systemd services. |
103 | | - |
104 | | -  |
105 | | -
|
106 | | - - Using **`journalctl`** commands print all the log entries from oldest to the newest. |
107 | | - - Using **`journalctl -b`** command print all the logs from the current boot. |
108 | | - - Using **`journalctl -u docker.service`** command print all the logs specific to the unit specified, for example docker in this case. |
109 | | -
|
110 | | - ``` |
111 | | - [~]$ journalctl |
112 | | - ``` |
113 | | -
|
114 | | - ``` |
115 | | - [~]$ journalctl -b |
116 | | - ``` |
117 | | -
|
118 | | - ``` |
119 | | - [~]$ journalctl -u docker.service |
120 | | - ``` |
| 18 | +### Systemctl Commands |
| 19 | + |
| 20 | +- To start a service use the start command, for example to start a docker service use **`systemctl start docker`** |
| 21 | + |
| 22 | + ``` |
| 23 | + [~]$ systemctl start docker |
| 24 | + ``` |
| 25 | + |
| 26 | +- To stop a service use the stop command, for example to stop a docker service use **`systemctl stop docker`** |
| 27 | + |
| 28 | + ``` |
| 29 | + [~]$ systemctl stop docker |
| 30 | + ``` |
| 31 | +- To restart a service use the restart command, for example to restart a docker service use **`systemctl restart docker`** this will stop and start again. |
| 32 | + |
| 33 | + ``` |
| 34 | + [~]$ systemctl restart docker |
| 35 | + ``` |
| 36 | +- To reload a service use the reload command, for example to reload a docker service use **`systemctl reload docker`**, this will reload all the configuration without interrupting the normal functionaltiy of the service |
| 37 | + |
| 38 | + ``` |
| 39 | + [~]$ systemctl reload docker |
| 40 | + ``` |
| 41 | +- To enable a service and make it persistent accross reboots use the enable command, for example to enable a docker service use **`systemctl enable docker`** |
| 42 | + |
| 43 | + ``` |
| 44 | + [~]$ systemctl enable docker |
| 45 | + ``` |
| 46 | + |
| 47 | +- To disable a service at boot use the disable command, for example to disable a docker service use **`systemctl disable docker`** command. |
| 48 | + |
| 49 | + ``` |
| 50 | + [~]$ systemctl disable docker |
| 51 | + ``` |
| 52 | + |
| 53 | +- To know the status of the service use **`systemctl status docker`** command. This command provided the state of the service. If running properly is should show **`active (running)`** state as shown in screenshot below. |
| 54 | + |
| 55 | + ``` |
| 56 | + [~]$ systemctl status docker |
| 57 | + ``` |
| 58 | + |
| 59 | +- Besides **`active (running)`** state there are few other state that you should be aware off. |
| 60 | + |
| 61 | +  |
| 62 | + |
| 63 | +- Running **`systemctl daemon reload`** command after making changes to service unit file reloads the system manager configuration and makes the systemd aware of the changes. |
| 64 | + |
| 65 | +- To edit the service file use command **`systemctl edit project-mercury.service --full`** this will open a text editor, you can make the changes and re-write the settings as needed, making changing this way applied immediately without running the **`systemctl daemon reload`** command |
| 66 | + |
| 67 | + ``` |
| 68 | + [~]$ systemctl daemon-reload |
| 69 | + [~]$ systemctl edit project-mercury.service --full |
| 70 | + ``` |
| 71 | +- To see the current runlevel use **`systemctl get-default`** |
| 72 | + |
| 73 | + ``` |
| 74 | + [~]$ systemctl get default |
| 75 | + ``` |
| 76 | + |
| 77 | +- To change the runleve to a different target use **`systemctl set-default multi-user.target`** |
| 78 | + |
| 79 | + ``` |
| 80 | + [~]$ systemctl set-default multi-user.target |
| 81 | + ``` |
| 82 | + |
| 83 | +- To list all the units that systemd has loaded use **`systemctl list-units --all`**, this lists all the unit which are active, inactive or anyother state. |
| 84 | + |
| 85 | + ``` |
| 86 | + [~]$ systemctl list-units --all |
| 87 | + ``` |
| 88 | + |
| 89 | +- To list only active units use **`systemctl list-units`** command |
| 90 | + |
| 91 | + ``` |
| 92 | + [~]$ systemctl list-units |
| 93 | + ``` |
| 94 | + |
| 95 | +- To view, and also locate a unit file use **`systemctl cat`** command. A comment line containing the path to the unit file is printed as the first line of output. |
| 96 | + |
| 97 | + ``` |
| 98 | + [~]$ systemctl cat project-mercury.service |
| 99 | + ``` |
| 100 | + |
| 101 | +## JOURNALCTL |
| 102 | + |
| 103 | + - __Journalctl__ is a command for quering/viewing logs collected by systemd. |
| 104 | + - The systemd-journald service is responsible for systemd’s log collection, and it retrieves messages from the kernel systemd services, and other sources. |
| 105 | + - Very useful when you are troubleshooting issues with systemd services. |
| 106 | + |
| 107 | +  |
| 108 | + |
| 109 | + - Using **`journalctl`** commands print all the log entries from oldest to the newest. |
| 110 | + |
| 111 | + ``` |
| 112 | + [~]$ journalctl |
| 113 | + ``` |
| 114 | + - Using **`journalctl -b`** command print all the logs from the current boot. |
| 115 | +
|
| 116 | + ``` |
| 117 | + [~]$ journalctl -b |
| 118 | + ``` |
| 119 | + - Using **`journalctl -u docker.service`** command print all the logs specific to the unit specified, for example docker in this case. |
| 120 | +
|
| 121 | + ``` |
| 122 | + [~]$ journalctl -u docker.service |
| 123 | + ``` |
| 124 | +
|
| 125 | + - Using **`journalctl -u docker.service --since`** command print all the logs specific to the unit specified since the given time, for example docker in this case. |
| 126 | +
|
| 127 | + ``` |
| 128 | + [~]$ journalctl -u docker.service --since "2022-01-01 13:45:00" |
| 129 | + ``` |
| 130 | +
|
121 | 131 | ## HANDS-ON LABS |
122 | 132 |
|
123 | 133 | - Now lets troubleshoot and help **`Bob`** [Let's Help Bob](https://kodekloud.com/courses/the-linux-basics-course/lectures/17074647) |
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