Install and make GNU GCC 10 default in Ubuntu 20.04 Focal

The best way to install and use GNU GCC 10 is to install first, build-essential package, which will pull in the GNU GCC 9.2, and then install the GNU GCC 10. In fact, it is possible to install only GNU GCC 10 packages, but build-essential brings with it many additional packages, which are mandatory for the configuration and compiling stages.
GNU GCC is included in the official Ubuntu Focal repository! It just needs to be installed and made to be the default compiler.

Install build-essential ensures all generic packages to be installed, which are involved in the building process of a software product.

There are three steps to install and use GNU GCC 10 under Ubuntu 20.04:

  1. Install build-essential package.
  2. Install gcc-10 packages (g++, too).
  3. Make GNU GCC 10 default compiler – use update-alternatives to point the GNU GCC 10 as the default compiler

Four simple lines and the third is a little bit more complex:

apt update -y
apt upgrade -y
apt install -y build-essential
apt install -y gcc-10 g++-10 cpp-10
update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 100 --slave /usr/bin/g++ g++ /usr/bin/g++-10 --slave /usr/bin/gcov gcov /usr/bin/gcov-10

Always update and upgrade before installing new software. Use sudo before each command, if installation is performed by a user other than root:

sudo apt update -y
sudo apt upgrade -y
sudo apt install -y build-essential
sudo apt install -y gcc-10 g++-10 cpp-10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 100 --slave /usr/bin/g++ g++ /usr/bin/g++-10 --slave /usr/bin/gcov gcov /usr/bin/gcov-10

It is a good idea to install cmake package, in addition to the above, because cmake is not included in build-essential:

apt install -y cmake

The apt output of installing GNU GCC 10

Many additional packages like multiple perl modules, libraries and make are installed.
Keep on reading!

Changing the queueing discipline – Error: Cannot delete qdisc with handle of zero.

If trying to delete a qdisc root to set no rules and no queuing algorithm probably for the purpose to add a new one a replace command is the right option!
An error saying there are no existing rules:

[root@srv ~]# tc qdisc del dev ens1f0 root
Error: Cannot delete qdisc with handle of zero.

Changing the qdisc with another. The example below replaces the MQ (multiqueues) with FQ (Fair Queue policy):

[root@srv ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens1f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq state UP group default qlen 1000
    link/ether b4:96:54:9f:10:71 brd ff:ff:ff:ff:ff:ff
    inet 84.16.231.24/26 brd 84.16.231.63 scope global noprefixroute ens1f0
       valid_lft forever preferred_lft forever
    inet6 fe80::b696:91ff:fe8e:860/64 scope link 
       valid_lft forever preferred_lft forever
[root@srv ~]# tc qdisc replace dev ens1f0 root fq
[root@srv ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens1f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether b4:96:54:9f:10:71 brd ff:ff:ff:ff:ff:ff
    inet 84.16.231.24/26 brd 84.16.231.63 scope global noprefixroute ens1f0
       valid_lft forever preferred_lft forever
    inet6 fe80::b696:91ff:fe8e:860/64 scope link 
       valid_lft forever preferred_lft forever

The replace command is used,but the add command has the same effect in this case. del cannot remove the queueing discipline from a physical network device. noqueue might be only special devices like loopback (i.e. localhost), bonding network devices and so on.

In CentOS, for additional kernel modules use kernel-modules-extra package if some qdiscs are missing.

OpenVPN stops working after network restart

Encountering the following problem – OpenVPN works perfectly when started or restarted, but when the network connection of the computer restarts or for example, the WIFI device resets (or loses the wifi network and connects again when it becomes available) the VPN never recovers. All networks routed via the VPN never seem to work again and they become dead ends to the computer despite the Internet connectivity is OK.
The logs show only attempts to connect again to the servers, but apparently with no success:

....
Oct 13 02:22:55 www openvpn[7744]: Attempting to establish TCP connection with [AF_INET]111.111.111.111:12345 [nonblock]
....
Oct 13 02:24:55 www openvpn[7744]: TCP: connect to [AF_INET]111.111.111.111:12345 failed: Connection timed out
....
Oct 13 02:22:55 www openvpn[7744]: Attempting to establish TCP connection with [AF_INET]111.111.111.111:12345 [nonblock]
....
Oct 13 02:24:55 www openvpn[7744]: TCP: connect to [AF_INET]111.111.111.111:12345 failed: Connection timed out

The server 111.111.111.111 is unreachable and it stays unreachable even the network connectivity recovered and the Internet of the computer is OK.
In this case, the OpenVPN server is part of a route network push to the client, and the OpenVPN IP is part of the pushed network to be routed via the VPN. And when the client’s network connection resets, the additional server’s IP route to the gateway disappears, but the pushed route does not, and now the OpenVPN server’s IP is part of a VPN route, which is dead because the VPN channel is dead. A restart of all OpenVPN routes is required (remove the special VPN device tun device with its routes and then add the device and routes again after successful reconnection to the OpenVPN server), but when an OpenVPN client option persist-tun is in the configuration, the restart won’t happen in the mentioned way. Only a restart of the service will remove the tun and its routes and then add them after a successful reconnection to the OpenVPN server.

Removing the persist-tun from the client’s configuration will trigger a full restart of the VPN channel – remove the special tun device and all OpenVPN routes and then reconnect and initialize the special tun device and then add the pushed routes.

Here is the example:

  • The OpenVPN server’s IP is 111.111.111.111.
  • The OpenVPN server pushes several networks to the client. Networks, which must be routed via the VPN. One of them happened to be 111.111.111.0/24, which includes the OpenVPN server’s IP.
  • The OpenVPN server adds a route for its IP to be routed via the default client’s gateway, which is 192.168.0.1. This is how the VPN channel works despite it pushed the whole network 111.111.111.0/24 via the VPN.

The problem appears when the network resets and the client’s OpenVPN process removes the route for the OpenVPN IP via the gateway because the gateway is not valid anymore! With persist-tun the pushed OpenVPN routes won’t be removed only reconnect attempts will be tried. But the OpenVPN IP now routes via the pushed server’s route via the dead VPN channel.
Keep on reading!

Transfer only a list of files with rsync

Transferring a list of files from one server to another maybe not so easy as it looks like, if the list consists of files with symlinks in the paths. Consider the following example:

/mnt/storage1/dir1/subdir1/file1
/mnt/storage1/dir1/subdir2/file2
/mnt/storage1/dir1/subdir3/file3

But what if the subdir3 is a symlink to a sub-directory:

/mnt/storage1/dir1/subdir3 -> /mnt/storage2/dir1/subdir3

STEP 1) Generate a list of only files following the symlinks if they exist.

The best way is to use Linux command find:

find -L /mnt/storage1/ -type f &> find.files.log

The option “-L” instructs the find to follow symbolic links and the test for the file (-type f) will always match against the type of the file that the symbolic link points to and not the symlink itself.

STEP 2) rsync the list of the files

There are several options (–copy-links –copy-dirlinks), which must be used with rsync command to be able to transfer the list of files, which may include symlink directories in the files’ paths:

rsync --copy-links --copy-dirlinks --partial --files-from=/root/find.files.log --verbose --progress --stats --times --perms --owner --group 10.10.10.10::storage /

The command above uses the rsync daemon started on the source server with shared root under the name “root” in the rsync configuration. Here is a sample rsync daemon configuration (/etc/rsyncd.conf):

pid file = /run/rsyncd.pid
use chroot = yes
read only = yes
hosts allow = 10.10.10.10/24
hosts deny = *

[root]
        uid=0
        gid=0
        path = /
        comment = root partition
        exclude = /proc /sys

Of course, a relative path could be used in the rsync daemon configuration if the file generated is also a relative path. For simplicity, here the whole real path is used.

In addition, the rsync could be used without a rsync daemon, but in conjunction with ssh daemon:

rsync --rsh='ssh -p 22 -l root' --copy-links --copy-dirlinks --partial --files-from=/root/find.files.log --verbose --progress --stats --times --perms --owner --group 10.10.10.10:/ /

Again, because the files in the find.files.log are with absolute paths the root / must be used in the rsync command. Relative paths may be used, too.

Stopping the glusterfs volume releases disk sleep process hangs

A quick tip for GlusterFS volume. There are multiple possible reasons for a Linux process to hang in “Disk Sleep” state, which even the KILL -9 cannot interrupt:

  • a bug in GlusterFS
  • just bad options turn on online
  • other device relying on a GlusterFS, which is unavailable.
[17294588.184470] INFO: task gdisk:12505 blocked for more than 120 seconds.
[17294588.184538] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[17294588.184628] gdisk           D ffff8ce01fb9acc0     0 12505  26866 0x00000080
[17294588.184780] Call Trace:
[17294588.184844]  [<ffffffffbaed3d81>] ? __wake_up_common_lock+0x91/0xc0
[17294588.184910]  [<ffffffffbb585da9>] schedule+0x29/0x70
[17294588.184974]  [<ffffffffbb5838b1>] schedule_timeout+0x221/0x2d0
[17294588.185037]  [<ffffffffbaed3dc3>] ? __wake_up+0x13/0x20
[17294588.185102]  [<ffffffffc0a05d2e>] ? loop_make_request+0x12e/0x210 [loop]
[17294588.185169]  [<ffffffffbaf06d32>] ? ktime_get_ts64+0x52/0xf0
[17294588.185232]  [<ffffffffbb58549d>] io_schedule_timeout+0xad/0x130
[17294588.185304]  [<ffffffffbb5863dd>] wait_for_completion_io+0xfd/0x140
[17294588.185369]  [<ffffffffbaedb990>] ? wake_up_state+0x20/0x20
[17294588.185468]  [<ffffffffbb157e64>] blkdev_issue_flush+0xb4/0x110
[17294588.185533]  [<ffffffffbb08d335>] blkdev_fsync+0x35/0x50
[17294588.185598]  [<ffffffffbb082f57>] do_fsync+0x67/0xb0
[17294588.185671]  [<ffffffffbb083240>] SyS_fsync+0x10/0x20
[17294588.185734]  [<ffffffffbb592ed2>] system_call_fastpath+0x25/0x2a
[17294708.187598] INFO: task gdisk:12505 blocked for more than 120 seconds.
[17294708.187664] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[17294708.187753] gdisk           D ffff8ce01fb9acc0     0 12505  26866 0x00000080
[17294708.187905] Call Trace:
[17294708.187968]  [<ffffffffbaed3d81>] ? __wake_up_common_lock+0x91/0xc0
[17294708.188033]  [<ffffffffbb585da9>] schedule+0x29/0x70
[17294708.188096]  [<ffffffffbb5838b1>] schedule_timeout+0x221/0x2d0
[17294708.188159]  [<ffffffffbaed3dc3>] ? __wake_up+0x13/0x20
[17294708.188223]  [<ffffffffc0a05d2e>] ? loop_make_request+0x12e/0x210 [loop]
[17294708.188289]  [<ffffffffbaf06d32>] ? ktime_get_ts64+0x52/0xf0
[17294708.188352]  [<ffffffffbb58549d>] io_schedule_timeout+0xad/0x130
[17294708.188416]  [<ffffffffbb5863dd>] wait_for_completion_io+0xfd/0x140
[17294708.188480]  [<ffffffffbaedb990>] ? wake_up_state+0x20/0x20
[17294708.188545]  [<ffffffffbb157e64>] blkdev_issue_flush+0xb4/0x110
[17294708.188624]  [<ffffffffbb08d335>] blkdev_fsync+0x35/0x50
[17294708.188690]  [<ffffffffbb082f57>] do_fsync+0x67/0xb0
[17294708.188754]  [<ffffffffbb083240>] SyS_fsync+0x10/0x20
[17294708.188828]  [<ffffffffbb592ed2>] system_call_fastpath+0x25/0x2a

The above example of dmesg log shows the gdisk process stuck in “Disk Sleep” state, because of a loop device from a file on an unavailable GlusterFS volume! Kill -9 won’t help, the process will remain in this bad state and even a restart would be difficult to perform!

[root@srv1 ~]# gluster volume stop VOL2 
Stopping volume will make its data inaccessible. Do you want to continue? (y/n) y
volume stop: VOL2: success
[root@srv1 ~]# gluster volume start VOL2 
volume start: VOL2: success

The solution is to stop the GlusterFS Volume and all the blocked processes on bad devices such as above would be released. The processes will carry on executing or will end their execution after issuing a stop command to the volume. No problem to start the GlusterFS volume immediately after the stop!
NOTE: executing STOP command would affect all servers using this volume. The volume becomes inaccessible for all!

Repairing damaged backup GPT with gdisk

Problem with network shared storage could lead to a damaged file system or even GPT tables, so the gdisk may help in this case.
Here it is a nasty the error:

[root@srv1 ~]# kpartx /dev/loop0
Alternate GPT is invalid, using primary GPT.
loop0p1 : 0 83881984 /dev/loop0 2048
[root@srv1 ~]# parted /dev/loop0
GNU Parted 3.1
Using /dev/loop0
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p                                                                
Error: The backup GPT table is corrupt, but the primary appears OK, so that will be used.
OK/Cancel? OK                                                             
Model: Loopback device (loopback)
Disk /dev/loop0: 42.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name     Flags
 1      1049kB  42.9GB  42.9GB               primary

(parted)

So parted reports the backup GPT is damaged, but how to fix it? The solution is to use gdisk and use write “w” command in it. gdisk also shows the exact error with the GPT table with “v” option:

[root@srv1 ~]# gdisk 
GPT fdisk (gdisk) version 0.8.10

Type device filename, or press <Enter> to exit: /dev/loop0
Warning! Main and backup partition tables differ! Use the 'c' and 'e' options
on the recovery & transformation menu to examine the two tables.

Warning! One or more CRCs don't match. You should repair the disk!

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: damaged

****************************************************************************
Caution: Found protective or hybrid MBR and corrupt GPT. Using GPT, but disk
verification and recovery are STRONGLY recommended.
****************************************************************************

Command (? for help): p
Disk /dev/loop0: 83886080 sectors, 40.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 7EDF123B-FBC4-4C09-B636-922BD165F862
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 83886046
Partitions will be aligned on 2048-sector boundaries
Total free space is 4029 sectors (2.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048        83884031   40.0 GiB    0700  primary

Command (? for help): v

Caution: The CRC for the backup partition table is invalid. This table may
be corrupt. This program will automatically create a new backup partition
table when you save your partitions.

Identified 1 problems!

Command (? for help): p
Disk /dev/loop0: 83886080 sectors, 40.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 7EDF123B-FBC4-4C09-B636-922BD165F862
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 83886046
Partitions will be aligned on 2048-sector boundaries
Total free space is 4029 sectors (2.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048        83884031   40.0 GiB    0700  primary

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): Y
OK; writing new GUID partition table (GPT) to /dev/loop0.

Warning: The kernel is still using the old partition table.
The new table will be used at the next reboot.
The operation has completed successfully.

And the GPT backup in this loop device is fixed. Executing parted again reports no problems:

[root@srv1 ~]# parted /dev/loop0 print
Model: Loopback device (loopback)
Disk /dev/loop0: 42.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name     Flags
 1      1049kB  42.9GB  42.9GB               primary

Verify also reports nor error. More options are available:

[root@srv1 ~]# gdisk /dev/loop0
GPT fdisk (gdisk) version 0.8.10

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): h
b  back up GPT data to a file
c  change a partition's name
d  delete a partition
i  show detailed information on a partition
l  list known partition types
n  add a new partition
o  create a new empty GUID partition table (GPT)
p  print the partition table
q  quit without saving changes
r  recovery and transformation options (experts only)
s  sort partitions
t  change a partition's type code
v  verify disk
w  write table to disk and exit
x  extra functionality (experts only)
?  print this menu

Command (? for help): v

No problems found. 4029 free sectors (2.0 MiB) available in 2
segments, the largest of which is 2015 (1007.5 KiB) in size.

Command (? for help): q

Force losetup detach of local file after it became unavailable

Mounting a file as loop devices is simple enough operation! But what if the file just disappears because of the network storage got unreachable?

In our case the shared network storage had got unavailable and the ext4 file system of the loop device got read-only! Unfortunately after the reset of the shared network storage and mounting it in the same place, the loop device (/dev/loop0) still maintained the old file descriptor to the unavailable file. And the losetup could not detach the device, at all.

root@srv ~# losetup -d /dev/loop0
root@srv ~# losetup -l
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE
/dev/loop0         0      0         0  0 /mnt/storage4/servers/test_raw_image.img
[root@lsrv1 ~]# kpartx -df /dev/loop0
read error, sector 0
read error, sector 1
read error, sector 29

The above command could not detach the device. Unfortunately, the losetup does not have the force detach, so the server ended with blocked loop0 device pointing to unavailable file. kpartx does not work, neither.

The solution is to use dmsetup!

root@srv ~# dmsetup remove /dev/mapper/loop0p1
root@srv ~# losetup -l
root@srv ~#

And there is no loop device any more. The wrong pointing loop device has been removed successfully! Now the user can use the loop0 for another device and in many cases, this helps to umount the filesystem!

removing the default kernel in CentOS 8 – remove elrepo kernel

Removing the default kernel aka the loaded kernel in CentOS 8 maybe challenging because the package is protected and cannot be removed by the yum or dnf.
Here is the case: an elrepo kernel-ml loaded and the dnf prints it cannot remove the package, because it is protected:

[root@srv ~]# dnf remove kernel-ml kernel-ml-core kernel-ml-modules
Error: 
 Problem: The operation would result in removing the following protected packages: kernel-ml-core
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)
[root@srv ~]# uname -a
Linux srv.localhost 5.10.4-1.el8.elrepo.x86_64 #1 SMP Tue Dec 29 11:04:23 EST 2020 x86_64 x86_64 x86_64 GNU/Linux
[root@srv ~]# grubby --default-kernel
/boot/vmlinuz-5.10.4-1.el8.elrepo.x86_64

The system is booted up with the kernel we are trying to remove, which is impossible.

The solution is to set a new default kernel and load it. Then dnf will be able to remove the first kernel.

For CentOS 7, just use the yum instead of dnf command.
Using grubby is really easy and straightforward:

STEP 1) List all installed and available to boot kernels

[root@srv ~]# grubby --info=ALL |grep ^kernel
kernel="/boot/vmlinuz-5.10.4-1.el8.elrepo.x86_64"
kernel="/boot/vmlinuz-4.18.0-259.el8.x86_64"
kernel="/boot/vmlinuz-4.18.0-257.el8.x86_64"
kernel="/boot/vmlinuz-0-rescue-45e12f0814fd4947b99cbdcb88950361"

STEP 2) Select the kernel to load the next time

[root@srv ~]# grubby --set-default "/boot/vmlinuz-4.18.0-259.el8.x86_64"
The default is /boot/loader/entries/45e12f0814fd4947b99cbdcb88950361-4.18.0-259.el8.x86_64.conf with index 1 and kernel /boot/vmlinuz-4.18.0-259.el8.x86_64

Keep on reading!

Booting network installation from ipxe disk using IPMI KVM

There is a project for extended PXE Boot features https://ipxe.org/. This article is not for describing what this project may offer, but to show how to boot any Linux distribution (in fact, Windows 10, too) network installation wizard using the virtual CD/DVD of an IPMI KVM, DELL’s DRAC, HP iLO, IBM RSA/IMM and in general, KVM over IP.
Using the iPXE CD bootable disk mounted in the virtual CD/DVD of the server’s remote console (IPMI KVM and so on) will allow:

  • Booting from a CD/DVD with only a 1M size.
  • Extends the PXE features of the server’s network card.
  • Manual set IP address, i.e. not relying on DHCP server. In addition of the DHCP feature, but DHCP feature requires DHCP server, which is not always the case.
  • Load a Linux kernel and initramfs from a URL.
  • Boot a Linux live or installation CD/DVD from an URL. The server could load the instllation wizard from an official mirror in the Internet.
  • Manual install – boot from 1M CD and continue with multi gigabyte installation from an URL. For comparision the CentOS 8 network installation disk is more than 600M versus 1M iPXE CD disk. Booting directly from a 600M CentOS 8 network installation disk is unstable and really slow when the disk is mounted in user’s KVM. And not alwyas is possible to mount a disk next to the server location (or in the same co-location).
  • Automated install – simple unattended installation with kickstart files without the need of speacial features of the dedicated service provider.
  • No software installation or code writting needed.

This article uses the iPXE CD to boot and manually set an IP and then load the Linux kernel and initramfs of the CentOS 8 installation disk using an official URL mirror on the Internet. All types of server’s KVM, which supports CD/DVD virtual device, can be used.

Just 1 Mbytes of CD/DVD is required to boot an installation of a (connected to the Internet) server/machine.

Here are the steps and correct (all lines are tested) command lines to boot an installation wizard. The server is a SUPERMICRO server with IPMI KVM for remote management.
The iPXE ISO file is located here http://boot.ipxe.org/ipxe.iso

SCREENSHOT 1) Open the IPMI KVM and click on “Virtual Storage” menu to open the image mount dialog.

main menu
Virtual Storage menu

Keep on reading!

xdg and autostart in Linux X server regardless the desktop environment

There is a tool xdg, which manages application integration with the different GUI Desktops in the Linux world. One of the features it offers is to autostart an application when the X window system starts and it is perfectly normal to have a bunch of running programs that cannot be found in the Windowing manager settings like KDE System Settings -> Autostart, GNOME Tweak tool and Autostart and so on.

xdg offers autostart of Linux appilcations mainly Desktop when the GUI windowing system starts

There two main paths to look for entries to autostart:

  1. /etc/xdg/autostart – called system-wide and most of the application will place files when they are installed.
  2. [user’s home]/.config/autostart – user’s applications to start when the user logs in .

With xdg autostart feature the user can explain himself why the Windowing systems like KDE or GNOME start tens of applications (not exactly related to the base GUI windowing system).

There is a security problem here, which is sometimes installing a package will place an autostart file there because the maintainer decided it is important but the package might be just a dependency and the next time the user logs in unwanted program might execute and open ports!

For example, Rygel is an open-source UPnP/DLNA MediaServer and it might be installed as a dependency but it places an autostart file, which starts a UPnP/DLNA server and exports the /home/[user’s directory]/Videos, /home/[user’s directory]/Pictures and more to the local network. Another example is with the GNOME index system tracker and the tracker-store, which may easily eat the RAM, disk, CPU, battery on a system without GNOME but with a different GUI!

Here is what a typical Ubuntu 18.04 system might autostart

Keep on reading!