06. Services

Services

For some theory, see Managing Services with systemd by RedHat.

Mounting a disk with systemd

  1. Create a new Virtual Disk in VirtualBox.

    • 1

    2

    • 3

    4

  2. Boot the Virtual Machine.
  3. See the created disk. 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ su -
comp-core-i7-3615qm-0dbf32 ~ # fdisk -l

    5

  4. Run GParted to create partitions. 
    comp-core-i7-3615qm-0dbf32 ~ # gparted /dev/sdb

    6

    • 7

  5. Run fdisk to see the created partition. 
    comp-core-i7-3615qm-0dbf32 ~ # fdisk -l
    Output: 
    Device     Start    End Sectors  Size Type
/dev/sdb1   2048 260095  258048  126M Linux filesystem
  6. See information on currently mounted partitions. 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ df
Filesystem      Size  Used Avail Use% Mounted on
udevfs          985M     0  985M   0% /dev
runfs           993M  1.1M  992M   1% /run
/dev/sda2        30G  7.9G   21G  28% /
tmpfs           993M  4.0K  993M   1% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           993M     0  993M   0% /sys/fs/cgroup
tmpfs           993M  8.0K  993M   1% /tmp
tmpfs           199M  8.0K  199M   1% /run/user/500
  7. See manual page on mount unit configuration. 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ man systemd.mount
  8. See locations of systemd units. Non-modifiable units: 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ ls /lib/systemd/system -l
    Configurable units: 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ ls /etc/systemd/system -l
  9. See IDs of disk devices: 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ su -
Password:

comp-core-i7-3615qm-0dbf32 ~ # blkid
/dev/sda1: UUID="8adb69dd-b152-45b6-b4b0-4824f2282d2c" TYPE="swap"
/dev/sda2: UUID="a4ba36d4-a42e-48a6-ae91-7e2acbd71ce8" TYPE="ext4"
/dev/sr0: UUID="2020-04-02-21-43-51-00" LABEL="Simply Linux live 9.0 x86_64" TYPE="iso9660" PTUUID="333d32d7" PTTYPE="dos"
/dev/pktcdvd/pktcdvd0: UUID="2020-04-02-21-43-51-00" LABEL="Simply Linux live 9.0 x86_64" TYPE="iso9660" PTUUID="333d32d7" PTTYPE="dos"
/dev/sdb1: UUID="be221b17-728f-4636-9a6c-6cc2c2f97b4e" TYPE="ext4" PARTUUID="ab228d6f-ead7-4d5d-b436-1cd539d7f79b"

comp-core-i7-3615qm-0dbf32 ~ # ls /dev/disk/by-uuid/
2020-04-02-21-43-51-00                a4ba36d4-a42e-48a6-ae91-7e2acbd71ce8
8adb69dd-b152-45b6-b4b0-4824f2282d2c  be221b17-728f-4636-9a6c-6cc2c2f97b4e

comp-core-i7-3615qm-0dbf32 ~ # ls /dev/disk/by-id/ -l
total 0
lrwxrwxrwx 1 root root  9 May 12 19:10 ata-VBOX_CD-ROM_VB2-01700376 -> ../../sr0
lrwxrwxrwx 1 root root  9 May 12 23:30 ata-VBOX_HARDDISK_VB95f922ef-001cd0ee -> ../../sdb
lrwxrwxrwx 1 root root 10 May 12 23:30 ata-VBOX_HARDDISK_VB95f922ef-001cd0ee-part1 -> ../../sdb1
lrwxrwxrwx 1 root root  9 May 12 22:21 ata-VBOX_HARDDISK_VBe293c3d6-9409ce04 -> ../../sda
lrwxrwxrwx 1 root root 10 May 12 22:21 ata-VBOX_HARDDISK_VBe293c3d6-9409ce04-part1 -> ../../sda1
lrwxrwxrwx 1 root root 10 May 12 22:21 ata-VBOX_HARDDISK_VBe293c3d6-9409ce04-part2 -> ../../sda2
  10. Create new mount unit. 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ mcedit /etc/systemd/system/srv.mount
    Mount unit configuration: 
    [Unit]
Description=Additional drive

[Mount]
What=/dev/disk/by-id/ata-VBOX_HARDDISK_VB95f922ef-001cd0ee-part1
Where=/srv
Type=ext4
Options=defaults

[Install]
WantedBy=multi-user.target

  11. Verify the created unit (shoud not complain about your unit srv.mount): 

    comp-core-i7-3615qm-0dbf32 ~ # systemd-analyze verify srv.mount
/lib/systemd/system/alteratord.socket:6: ListenStream= references a path below legacy directory /var/run/, updating /var/run/alteratord/.socket → /run/alteratord/.socket; please update the unit file accordingly.
/lib/systemd/system/smb.service:10: PIDFile= references a path below legacy directory /var/run/, updating /var/run/smbd.pid → /run/smbd.pid; please update the unit file accordingly.
/lib/systemd/system/winbind.service:9: PIDFile= references a path below legacy directory /var/run/, updating /var/run/winbindd.pid → /run/winbindd.pid; please update the unit file accordingly.
/lib/systemd/system/nmb.service:10: PIDFile= references a path below legacy directory /var/run/, updating /var/run/nmbd.pid → /run/nmbd.pid; please update the unit file accordingly.
/lib/systemd/system/chronyd.service:10: PIDFile= references a path below legacy directory /var/run/, updating /var/run/chrony/chronyd.pid → /run/chrony/chronyd.pid; please update the unit file accordingly.
  12. Check the service status. 
    comp-core-i7-3615qm-0dbf32 ~ # systemctl status srv.mount
● srv.mount - Additional drive
   Loaded: loaded (/etc/systemd/system/srv.mount; disabled; vendor preset: disabled)
   Active: inactive (dead)
    Where: /srv
     What: /dev/disk/by-id/ata-VBOX_HARDDISK_VB95f922ef-001cd0ee-part1
  13. Start the service and check it status again. 
    comp-core-i7-3615qm-0dbf32 ~ # systemctl start srv.mount
comp-core-i7-3615qm-0dbf32 ~ # systemctl status srv.mount
● srv.mount - Additional drive
   Loaded: loaded (/etc/systemd/system/srv.mount; disabled; vendor preset: disabled)
   Active: active (mounted) since Wed 2020-05-13 00:21:09 MSK; 1s ago
    Where: /srv
     What: /dev/sdb1
    Tasks: 0 (limit: 2361)
   Memory: 84.0K
   CGroup: /system.slice/srv.mount

May 13 00:21:09 comp-core-i7-3615qm-0dbf32 systemd[1]: Mounting Additional drive...
May 13 00:21:09 comp-core-i7-3615qm-0dbf32 systemd[1]: Mounted Additional drive.
comp-core-i7-3615qm-0dbf32 ~ #
  14. See the newly mounted disk. 
    comp-core-i7-3615qm-0dbf32 ~ # df
Filesystem      Size  Used Avail Use% Mounted on
udevfs          985M     0  985M   0% /dev
runfs           993M  1.1M  992M   1% /run
/dev/sda2        30G  7.9G   21G  28% /
tmpfs           993M  4.0K  993M   1% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           993M     0  993M   0% /sys/fs/cgroup
tmpfs           993M  8.0K  993M   1% /tmp
tmpfs           199M  8.0K  199M   1% /run/user/500
/dev/sdb1       119M  1.6M  108M   2% /srv
  15. Enable the service. 
    comp-core-i7-3615qm-0dbf32 ~ # systemctl enable srv.mount
Created symlink /etc/systemd/system/multi-user.target.wants/srv.mount → /etc/systemd/system/srv.mount.
comp-core-i7-3615qm-0dbf32 ~ #
  16. See service dependencies. 
    comp-core-i7-3615qm-0dbf32 ~ # systemctl list-dependencies srv.mount
srv.mount
● ├─-.mount
● ├─dev-disk-by\x2did-ata\x2dVBOX_HARDDISK_VB95f922ef\x2d001cd0ee\x2dpart1.device
● ├─dev-sdb1.device
● └─system.slice
  17. For note: classical approach to disk mounting: 
    comp-core-i7-3615qm-0dbf32 ~ # cat /etc/fstab
proc            /proc                   proc    nosuid,noexec,gid=proc          0 0
devpts          /dev/pts                devpts  nosuid,noexec,gid=tty,mode=620  0 0
tmpfs           /tmp                    tmpfs   nosuid                          0 0
UUID=a4ba36d4-a42e-48a6-ae91-7e2acbd71ce8       /       ext4    relatime        1       1
UUID=8adb69dd-b152-45b6-b4b0-4824f2282d2c       swap    swap    defaults        0       0

Running a service with systemd

  1. Install a compiler if it is not already installed. 
    comp-core-i7-3615qm-0dbf32 ~ # apt-get install gcc

  2. Take TCP echo server from the lecture and compile it. 

    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ cc tcp_echo_serverSR.c -o echosrv
  3. Copy the compiled program to a system folder. 
    comp-core-i7-3615qm-0dbf32 ~ # cp /home/andrewt/echosrv /usr/local/sbin/
    See the destination folder: 
    comp-core-i7-3615qm-0dbf32 ~ # ls  /usr/local/sbin/
echosrv
    Test the program: 
    comp-core-i7-3615qm-0dbf32 ~ # echosrv 0.0.0.0 1234 &
[1] 4905
comp-core-i7-3615qm-0dbf32 ~ # netcat localhost 1234
hello!
Received 7 bytes from 127.0.0.1, port 36514
hello!
comp-core-i7-3615qm-0dbf32 ~ # kill 4905
comp-core-i7-3615qm-0dbf32 ~ # [1]+  Завершено      echosrv 0.0.0.0 1234
  4. See manual page on service unit configuration. 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ man systemd.service
  5. Register TCP echo server as a service. Create a service unit: 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ su -
Password:
comp-core-i7-3615qm-0dbf32 ~ # mcedit /etc/systemd/system/echosrv.service
    With the following content: 
    [Unit]
Description=Echo service
After=network.target

[Service]
Type=simple
User=nobody
ExecStart=/usr/local/sbin/echosrv 0.0.0.0 1234

[Install]
WantedBy=multi-user.target
  6. Verify the created service unit. 
    comp-core-i7-3615qm-0dbf32 ~ # systemd-analyze verify echosrv.service
  7. Check the service status. 
    comp-core-i7-3615qm-0dbf32 ~ # systemctl status  echosrv.service
● echosrv.service - Echo service
   Loaded: loaded (/etc/systemd/system/echosrv.service; disabled; vendor preset: disabled)
   Active: inactive (dead)
  8. Start the service and check its status again. 
    comp-core-i7-3615qm-0dbf32 ~ # systemctl start  echosrv.service
comp-core-i7-3615qm-0dbf32 ~ # systemctl status  echosrv.service
● echosrv.service - Echo service
   Loaded: loaded (/etc/systemd/system/echosrv.service; disabled; vendor preset: disabled)
   Active: active (running) since Wed 2020-05-13 01:27:42 MSK; 3s ago
 Main PID: 4956 (echosrv)
    Tasks: 1 (limit: 2361)
   Memory: 156.0K
   CGroup: /system.slice/echosrv.service
           └─4956 /usr/local/sbin/echosrv 0.0.0.0 1234
  9. See who is listening sockets. 
    comp-core-i7-3615qm-0dbf32 ~ # netstat -ltp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 *:netbios-ssn               *:*                         LISTEN      2334/smbd
tcp        0      0 *:1234                      *:*                         LISTEN      4956/echosrv
tcp        0      0 localhost.localdomai:domain *:*                         LISTEN      4275/dnsmasq
tcp        0      0 *:ssh                       *:*                         LISTEN      2066/sshd
tcp        0      0 localhost.localdomain:ipp   *:*                         LISTEN      2041/cupsd
tcp        0      0 *:microsoft-ds              *:*                         LISTEN      2334/smbd
  10. Test the TCP echo service. 
    comp-core-i7-3615qm-0dbf32 ~ # netcat 0.0.0.0 1234
hello!
hello!

H/W

  1. Create 06_Services catalog on sugon server. All files should reside there.

  2. Finish all the tasks.
  3. Save information on the status of the services to text files. 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ systemctl status srv.mount > srv

andrewt@comp-core-i7-3615qm-0dbf32 ~ $ systemctl status echosrv.service > echosrv
  4. Upload the files to the 'sugon' server. To copy files to a folder on a remote server, use the 'scp' command: 
    scp /path/to/local/file username@hostname:/path/to/remote/file

scp username1@hostname1:/path/to/file username2@hostname2:/path/to/other/file
    For example: 
    andrewt@comp-core-i7-3615qm-0dbf32 ~ $ scp -P 2131 srv andrey@sugon:/home/andrey/06_Services
andrey@sugon's password:
srv                         100%  472    80.8KB/s   00:00

andrewt@comp-core-i7-3615qm-0dbf32 ~ $ scp -P 2131 echosrv andrey@sugon:/home/andrey/06_Services
andrey@sugon's password:
echosrv                    100%  447    71.1KB/s   00:00

    Note: I do not publish here 'sugon' IP. Please insert the valid IP yourself.

HSE/ArchitectureOS/Lab_06_Services (последним исправлял пользователь FrBrGeorge 2020-06-22 12:50:16)