System

Linux system tools, administration and tips

ArchLinux Upgrade Issues
CentOS Installation Issues
Changing Default S2RAM to USWSUSP Suspend Module
Fixing Incorrect Lid State by Hacking DSDT
JournalD Administration
Linux on Macbook Administration
SELinux - Services Blocked by SELinux
Standard CentOS Workstation Setup

ArchLinux Upgrade Issues

Error: key "ABCDE1282828181" could not be looked up remotely

Upgrade archlinux-keyring: pacman -S archlinux-keyring

Unable to get past login window after upgrading

This is caused by Nvidia driver being upgraded

nvidia-dkms: pacman -S nvidia-libgl

Failed to start load kernel modules after upgrade:

Possible causes:

broadcom-wl module
Solved by re-"makepkg" broadcom-wl from AUR
Find error message in systemctl status systemd-modules-load.service

CentOS Installation Issues

HP Microserver Gen 7

Kernel Panic on Boot (Both Live USB and New Installation)

Add the following lines to the kernel boot parameters: nolapic clocksource=hpet

Blank Screen on Startup

Append nomodeset to kernel param

Changing Default S2RAM to USWSUSP Suspend Module

If you have any issues to suspend your laptop e.g. suspend command doesn't work on your laptop, try changing the default sleep module to uswsusp:

Edit /etc/pm/config.d/module and add the following line: SLEEP_MODULE=uswsusp
Edit /etc/pm/config.d/defaults and add the following line: S2RAM_OPTS="-f"
Reboot and try to let her sleep.

References

Fixing Incorrect Lid State by Hacking DSDT

When I install a Linux distro to my VAIO notebook, I found that there is an annoying bug with the lid switch. It does not get updated whenever I suspend on lid close, it means cat /proc/acpi/button/lid/LID/state will output state: close. When I close the lid again, it won't suspend, instead, it will change the state to open. So in order for it to suspend again on lid close after the first suspend, I have to close it, reopen the lid and close it again.

I have tried installing Linux Mint, Fedora, Fuduntu and Xubuntu, but it is not fixed in any of the distros. So, I don't think it is distro problems. While researching this issues (which I spent two full days), I found that Linux got an amazing feature that enable users to dynamically loading DSDT at boot time, there is no need to update the BIOS. So here's the instuctions:

Install iasl using yum, apt-get or whatever package management you are using.

Extract DSDT:

$ sudo cat/sys/firmware/acpi/tables/DSDT > dsdt.aml

Disassemble dsdt.aml using the following command, this should create a new file dsdt.dsl:
```
$ iasl -d dsdt.aml
```
Compile it using:
```
$ iasl -tc dsdt.dsl
```
Fix any compiler errors, warnings and remarks. On my machine, the output is:
```
dsdt.dsl  1352:                         And (CTRL, 0x1E)
Warning  1106 -                                 ^ Result is not used, operator has no effect

dsdt.dsl  1584:                     0x00000000,         // Length
Error    4122 -                              ^ Invalid combination of Length and Min/Max fixed flags

dsdt.dsl  2443:                                 Name (_T_0, 0x00)
Remark   5111 -            Use of compiler reserved name ^  (_T_0)

dsdt.dsl  2521:                                 Name (_T_0, 0x00)
Remark   5111 -            Use of compiler reserved name ^  (_T_0)
```
a. The first one is on line 1352 can be fixed simply by changing And (CTRL, 0x1E) to And (CTRL, 0x1E, CTRL).
b. The second one is on line 1584, the length should be Range Maximum - Range Minimum + 1, on my machine, so fire up a hex calculator and start subtracting. On my machine, it's 0xE0000000 (0xDFFFFFFF - 0x00000000 + 0x00000001).
c. The third and fourth line is on line 2443 and 2521, because it uses a reserved name, simply replacing all instances of _T_0 to T_0 will stop the complaints. In vim, it is as simple as issuing :%s/_T_0/T_0/g in command mode.
Once everything is fixed (no errors, warning or remarks), add the following line to _WAK method, simply search for _WAK in dsdt.dsl:
```
If (LNotEqual (0x00, LIDS))
{
Store (0x00, LIDS)
Notify (\_SB.LID, 0x80)
}
```
NOTE 1: You might need to change \_SB.LID to match your path to LID method or on some machine LID0. Method name is preceded by an _ (underscore), so you can search for _LID in dsdt.dsl. After you found it, you have to determine the scope, scroll up until you found Scope keyword that your LID or LID0 method belongs to, inside the bracket is the scope name. It may be in more than one scope, so, it might be \_PCI0.SB.LID. If you specify an incorrect path to LID method, you will receive the following error:
```
dsdt.dsl 300: Notify (LID, 0x80)
Error 4068 - ^ Object is not accessible from this scope (LID_)
```
NOTE 2: What this function does is just to update the lid state once it is resumed from sleep. According to the ACPICA documentation, _WAK method is called by AcpiLeaveSleepState() function of ACPI. If the lid is open, the LIDS variable is 0x00, or 0x01 otherwise. So these few lines translate to "if lid state is not open (closed), change lid state to open and call LIDmethod".
Compile it using iasl -tc dsdt.dsl.

If no errors, warnings or remarks, add the following lines to /etc/grub.d/01_acpi:

# Uncomment to load custom ACPI table
GRUB_CUSTOM_ACPI="/boot/dsdt.aml"

# DON'T MODIFY ANYTHING BELOW THIS LINE!

prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib

. /usr/share/grub/grub-mkconfig_lib
#. ${libdir}/grub/grub-mkconfig_lib

# Load custom ACPI table
if [ x${GRUB_CUSTOM_ACPI} != x ] && [ -f ${GRUB_CUSTOM_ACPI} ] \
   && is_path_readable_by_grub ${GRUB_CUSTOM_ACPI}; then
   echo "Found custom ACPI table: ${GRUB_CUSTOM_ACPI}" >&2
   prepare_grub_to_access_device `${grub_probe} --target=device 
${GRUB_CUSTOM_ACPI}` | sed -e "s/^/  /"
   cat << EOF
acpi (\$root)`make_system_path_relative_to_its_root 
${GRUB_CUSTOM_ACPI}`
EOF
fi

Add executable bit to it:
```
$ sudo chmod +x /etc/grub.d/01_acpi
```
Copy the new dsdt.aml to /boot:
```
$ sudo cp dsdt.aml /boot
```

Regenerate grub.cfg:

$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg

Reboot

References

JournalD Administration

Optimizing JournalD Disk Space Usage

Edit /etc/systemd/journald.conf and change the following line:

SystemMaxUse=200M

To check disk space used by journald: journalctl --disk-usage

Linux on Macbook Administration

Blessing the Linux Kernel

Boot into Mac Recovery
Start terminal and enter:

bless --folder /Volumes/ARCH_EFI/EFI/arch/grub/ --file /Volumes/ARCH_EFI/EFI/arch/grub/grubx64.efi

Changing Apple keyboards (Macbook or USB) fnmode in Linux

Changing it temporarily, as root:

echo 2 > /sys/module/hid_apple/parameters/fnmode

Changing it Permanently:

Edit /etc/modprobe.d/hid_apple.conf and add the following line:

options hid_apple fnmode=2

SELinux - Services Blocked by SELinux

SELinux Blocked Apache Access to Files

setsebool -P httpd_unified 1
sudo /sbin/restorecon -R /var/www/html

VSFTPD OOPS Error

Issue the following command: setsebool -P ftp_home_dir 1

SSH bind port error permission denied

Issue the following command: semanage port –a –t ssh_port_t –p tcp 1234

Permission denied HTTP Error 403

Issue the following command: chcon -R --reference=/var/www /path/to/webroot

SELinux Denied HTTPD Access to MYSQLD on 127.0.0.1

grep mysqld /var/log/audit/audit.log | audit2allow -M mysqld
semodule -i mysqld.pp

SELinux Denied FTP Access to SMB Share

Try to login with ncftp first and you will see the error "OOPS: cannot change directory: /path/to/samba_share"
Execute command: su -c "grep ftpd_t /var/log/audit/audit.log | allow2audit -M ftpd_smb && semodule -i ftpd_smb"
Try to login again with ncftp and ls command will return empty list a although it isn't
Execute command: su -c "grep ftpd_t /var/log/audit/audit.log | allow2audit -M ftpd_smb && semodule -i ftpd_smb"
Execute command => sudo setsebool -P allow_ftpd_full_access on
Execute command => sudo setsebool -P ftp_home_dir on

Owncloud Custom Data Directory Denied

Assume owncloud data directory: /var/data

Install policycoreutils-python
/etc/init.d/restorecond start
chkconfig restorecond on
semanage fcontext -a -t httpd_sys_content_t '/var/data(/.*)?' 
restorecon -Rv /var/data

Standard CentOS Workstation Setup

Install GUI (MATE Desktop)

sudo yum install epel-release
sudo yum groupinstall 'X Window System'
sudo yum groupinstall 'MATE Desktop'
sudo systemctl isolate graphical.target
sudo systemctl set-default graphical.target

Install Printer

sudo yum install cups
sudo yum groupinstall "Development Tools"
sudo systemctl enable cups
sudo systemctl start cups
sudo yum install foomatic

Install drivers for the printer available at Open Printing

Optional - GUI WiFi Support

sudo yum install NetworkManager-wifi