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 (last edited 2020-06-22 09:50:16 by FrBrGeorge)